Patent Publication Number: US-2016243226-A1

Title: Combination Therapy With Anti-CD74 and Anti-CD20 Antibodies Provides Enhanced Toxicity to B-Cell Diseases

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 14/520,596, filed Oct. 22, 2014, which was a divisional of U.S. patent application Ser. No. 13/904,534, filed May 29, 2013 (now U.S. Pat. No. 8,906,378), which was a divisional of U.S. patent application Ser. No. 13/209,954, filed Aug. 15, 2011 (now U.S. Pat. No. 8,475,794), which claimed the benefit under 35 U.S.C. 119(e) of provisional U.S. Patent Application Ser. No. 61/374,751, filed Aug. 18, 2010; 61/374,772, filed Aug. 18, 2010; and 61/508,871, filed Jul. 18, 2011. U.S. Ser. No. 13/904,534 was a continuation-in-part of U.S. patent application Ser. No. 13/086,786, filed Apr. 14, 2011; Ser. No. 13/036,820, filed Feb. 28, 2011 (now U.S. Pat. No. 8,883,160); Ser. No. 13/021,302, filed Feb. 4, 2011 (now U.S. Pat. No. 8,246,960), (which was a divisional of U.S. Pat. No. 7,906,121; which was a divisional of U.S. Pat. No. 7,534,866); Ser. No. 13/012,977, filed Jan. 25, 2011, (which was a divisional of U.S. Pat. No. 7,906,118); Ser. No. 13/010,993, filed Jan. 21, 2011, (which was a divisional of U.S. Pat. No. 7,901,680); Ser. No. 13/004,349, filed Jan. 11, 2011; Ser. No. 12/968,936, filed Dec. 15, 2010 (now U.S. Pat. No. 8,906,377), (which was a divisional of U.S. Pat. No. 7,871,622; which was a divisional of U.S. Pat. No. 7,521,056); Ser. No. 12/964,021, filed Dec. 9, 2010; Ser. No. 12/949,536, filed Nov. 18, 2010, (which was a divisional of U.S. Pat. No. 7,858,070; which was a divisional of U.S. Pat. No. 7,527,787); Ser. No. 12/915,515, filed Oct. 29, 2010; Ser. No. 12/871,345, filed Aug. 30, 2010; Ser. No. 12/869,823, filed Aug. 27, 2010; Ser. No. 12/754,740, filed Apr. 6, 2010; Ser. No. 12/752,649, filed Apr. 1, 2010; Ser. No. 12/731,781, filed Mar. 25, 2010; Ser. No. 13/150,613, filed Jun. 1, 2011, (which was a divisional of U.S. Pat. No. 7,981,398; which was a divisional of U.S. Pat. No. 7,666,400); and Ser. No. 12/468,589, filed May 19, 2009, (which was a divisional of U.S. Pat. No. 7,550,143). Those applications claimed the benefit under 35 U.S.C. 119(e) of provisional U.S. Patent Applications 61/414,592, filed Nov. 17, 2010; 61/378,059, filed Aug. 30, 2010; 61/374,449, filed Aug. 17, 2010; 61/324,111, filed Apr. 14, 2010; 61/323,001, filed Apr. 12, 2010; 61/323,960, filed Apr. 14, 2010; 61/316,996, filed Mar. 24, 2010; 61/302,682, filed Feb. 9, 2010; 61/293,846, filed Jan. 11, 2010; 61/267,877, filed Dec. 9, 2009; 61/266,305, filed Dec. 3, 2009; 61/258,729, filed Nov. 6, 2009; 61/258,369, filed Nov. 5, 2009; 61/238,424, filed Aug. 31, 2009; 61/238,473, filed Aug. 31, 2009; 61/168,668, filed Apr. 13, 2009; 61/168,657, filed Apr. 13, 2009; 61/168,290, filed Apr. 10, 2009; 61/163,666, filed Mar. 26, 2009; 61/119,542, filed Dec. 3, 2008; 61/104,916, filed Oct. 13, 2008; 61/090,487, filed Aug. 20, 2008; 61/043,932, filed Apr. 10, 2008; 60/864,530, filed Nov. 6, 2006; 60/782,332, filed Mar. 14, 2006; 60/751,196, filed Dec. 16, 2005; 60/728,292, filed Oct. 19, 2005; 60/668,603, filed Apr. 6, 2005. 
    
    
     SEQUENCE LISTING 
     The instant application contains a Sequence Listing which has been submitted in ASCII format via EFS-Web and is hereby incorporated by reference in its entirety. Said ASCII copy, created on Aug. 15, 2011, is named IMM331US.txt and is 64,529 bytes in size. 
     FIELD OF THE INVENTION 
     The present invention concerns compositions and methods of use of combination therapy using at least one anti-CD74 antibody or antigen-binding fragment thereof and at least one other therapeutic agent. In preferred embodiments, the other therapeutic agent may be another antibody or fragment thereof against the same or a different target antigen, including but not limited to CD19, CD20, CD21, CD22, CD23, CD37, CD40, CD40L, CD52, CD80, IL-6, CXCR4 or HLA-DR. In other embodiments, the other therapeutic agent may be an immunomodulator, a cytotoxic agent, a drug, a toxin, an anti-angiogenic agent, a proapoptotic agent or a radionuclide. In more preferred embodiments, the anti-CD74 antibody or fragment may be administered in combination with another antibody or therapeutic agent as part of a dock-and-lock (DNL) complex, as described in detail below. Alternatively, the anti-CD74 and other therapeutic agent may be administered together or separately, with the other therapeutic agent administered before, concurrently with or after the anti-CD74 antibody. In most preferred embodiments, the combination of anti-CD74 antibody and second antibody or other therapeutic agent is significantly more efficacious for treating a disease than either agent administered alone or the sum of effects of the two agents administered separately. The combination may be highly effective for treating a disease in which CD74 is overexpressed in target cells, such as B cell lymphoma or leukemia (e.g., mantle cell lymphoma, multiple myeloma, Hodgkin&#39;s lymphoma, non-Hodgkin&#39;s lymphoma, diffuse large B cell lymphoma, Burkitt lymphoma, follicular lymphoma, acute lymphocytic leukemia, chronic lymphocytic leukemia, and hairy cell leukemia), solid tumors (e.g., glioblastoma, gastric cancer, bladder cancer, prostate cancer, thymic cancer, colorectal cancer, lung cancer, renal cancer, pancreatic cancer and breast cancer), autoimmune disease, immune dysfunction disease (e.g., graft-versus-host disease, organ transplant rejection), type-1 or type-2 diabetes. 
     BACKGROUND 
     To address the clinical concerns of immunogenicity and suboptimal pharmacokinetics, cancer therapy with monoclonal antibodies has evolved from murine to chimeric, humanized, and fully human constructs. Parallel to these improvements have been continuing efforts to develop more effective forms of antibodies, which to date include different antibody isotypes, single-chain antibody fragments with monomeric or multimeric binding moieties, specific mutations in the Fc region to modulate effector function or circulating half-life, and bispecific antibodies of numerous designs that vary in valency, structure, and constituents (Chames et al., Br J Pharmacol 2009, 157:220-233). 
     Because signaling pathway redundancies can result in lack of response to a single antibody, diverse strategies to use combination therapy with antibodies that bind to different epitopes or different antigens on the same target cell have been proposed. Combinations such as anti-CD20 and anti-CD22 (Stein et al., Clin Cancer Res 2004, 10:2868-2878), anti-CD20 and anti-HLA-DR (Tobin et al., Leuk Lymphoma 2007, 48:944-956), anti-CD20 and anti-TRAIL-R1 (Maddipatla et al., Clin Cancer Res 2007, 13:4556-4564), anti-IGF-1R and anti-EGFR (Goetsche et al., Int J Cancer 2005, 113:316-328), anti-IGF-1R and anti-VEGF (Shang et al., Mol Cancer Ther 2008, 7:2599-2608), or trastuzumab and pertuzumab that target different regions of human EGFR2 (Nahta et al., Cancer Res 2004, 64:2343-2346) have been evaluated preclinically, showing enhanced or synergistic antitumor activity in vitro and in vivo. 
     The first clinical evidence of an apparent advantage of combining two antibodies against different cancer cell antigens involved the administration of rituximab (chimeric anti-CD20) and epratuzumab (humanized anti-CD22 antibody) in patients with non-Hodgkin lymphoma (NHL). The combination was found to enhance anti-lymphoma efficacy without a commensurate increase in toxicity, based on 3 independent clinical trials (Leonard et al., J Clin Oncol 2005, 23:5044-5051; Strauss et al., J Clin Oncol 2006, 24:3880-86; Leonard and Goldenberg, Oncogene 2007, 26:3704-13). Although these results are promising, a need exists in the field for more effective antibody-based combination therapies. 
     SUMMARY 
     The present invention concerns improved compositions and methods of use of combination therapy with at least one anti-CD74 antibody or fragment thereof and a second antibody or fragment thereof or other therapeutic agent. In preferred embodiments, the combination is a trivalent, tetravalent or hexavalent construct made by the dock-and-lock (DNL) technique (see, e.g., U.S. Pat. Nos. 7,521,056; 7,527,787; 7,534,866; 7,550,143; 7,666,400; 7,858,070; 7,871,622; 7,901,680; 7,906,118 and 7,906,121, the Examples section of each of which is incorporated herein by reference.) The DNL technique takes advantage of the specific, high-affinity binding interaction between a dimerization and docking domain (DDD) sequence from the regulatory subunit of human cAMP-dependent protein kinase (PKA), such as human PKA RIα, RIβ, RIIα or RIIβ, and an anchor domain (AD) sequence from any of a variety of AKAP proteins. The DDD and AD peptides may be attached to any protein, peptide or other molecule. 
     Because the DDD sequences spontaneously dimerize and bind to the AD sequence, the DNL technique allows the formation of complexes between any selected molecules that may be attached to DDD or AD sequences. Although the standard DNL complex comprises a trimer with two DDD-linked molecules attached to one AD-linked molecule, variations in complex structure allow the formation of dimers, trimers, tetramers, pentamers, hexamers and other multimers. In some embodiments, the DNL complex may comprise two or more antibodies, antibody fragments or fusion proteins which bind to the same antigenic determinant or to two or more different antigens. The DNL complex may also comprise one or more other effectors, such as a cytokine, toxin or PEG moiety. 
     In preferred embodiments, hexavalent DNL constructs comprise an IgG molecule covalently attached to two copies of an AD moiety, which binds to four Fab fragments, each covalently attached to a DDD moiety. The hexavalent DNL construct therefore comprises six Fab moieties attached to an Fc moiety. By formation of disulfide bonds between the AD and DDD subunits, the entire DNL complex is highly stable under in vivo conditions and each Fab moiety retains the binding specificity and affinity of the parent antibody. In alternative embodiments, the hexavalent DNL construct may comprise 6 anti-CD74 Fabs; 4 anti-CD74 and 2 anti-CD20 Fabs; 2 anti-CD20 and 4 anti-CD74 Fabs; 4 anti-CD74 and 2 anti-CD22 Fabs; 2 anti-CD74 and 4 anti-CD22 Fabs; or other combinations of anti-CD74 with a second antibody, attached to an Fc moiety. The skilled artisan will realize that the constructs are not so limited, and DNL constructs comprising combinations of anti-CD74 antibody with antibodies against other known antigens, such as CD19, CD21, CD23, CD37, CD40, CD40L, CD52, CD80 IL-6, CXCR4, or HLA-DR may also be used. Previous studies have shown that such hexavalent constructs have distinct properties compared with their parental counterparts, including enhanced anti-lymphoma activity in vitro and comparable efficacy in vivo, despite showing shorter circulating half-lives (Rossi et al., Blood 2009, 113:6161-6171; Rossi et al., Cancer Res 2008, 68:8384-8392). 
     Although in preferred embodiments, the combination therapy with anti-CD74 antibody or fragment thereof and second antibody or other therapeutic agent may involve a DNL complex, in alternative embodiments the combination therapy may involve an anti-CD74 antibody or fragment thereof used in combination with a second antibody or fragment thereof or another therapeutic agent. The skilled artisan will be aware of many therapeutic agents of use for treatment of cancer, autoimmune disease or other B cell associated diseases that may be used in combination with an anti-CD74 antibody, such as the hLL1 antibody. 
     Many examples of anti-CD74 antibodies are known in the art and any such known antibody or fragment thereof may be utilized. In a preferred embodiment, the anti-CD74 antibody is an hLL1 antibody (also known as milatuzumab) that comprises the light chain complementarity-determining region (CDR) sequences CDR1 (RSSQSLVHRNGNTYLH; SEQ ID NO:1), CDR2 (TVSNRFS; SEQ ID NO:2), and CDR3 (SQSSHVPPT; SEQ ID NO:3) and the heavy chain variable region CDR sequences CDR1 (NYGVN; SEQ ID NO:4), CDR2 (WINPNTGEPTFDDDFKG; SEQ ID NO:5), and CDR3 (SRGKNEAWFAY; SEQ ID NO:6). A humanized LL1 (hLL1) anti-CD74 antibody suitable for use is disclosed in U.S. Pat. No. 7,312,318, incorporated herein by reference from Col. 35, line 1 through Col. 42, line 27 and  FIG. 1  through  FIG. 4 . However, in alternative embodiments, other known and/or commercially available anti-CD74 antibodies may be utilized, such as LS-B1963, LS-B2594, LS-B1859, LS-B2598, LS-05525, LS-C44929, etc. (LSBio, Seattle, Wash.); LN2 (BIOLEGEND®, San Diego, Calif.); PIN.1, SPM523, LN3, CerCLIP.1 (ABCAM®, Cambridge, Mass.); At14/19, Bu45 (SEROTEC®, Raleigh, N.C.); 1D1 (ABNOVA®, Taipei City, Taiwan); 5-329 (EBIOSCIENCE®, San Diego, Calif.); and any other antagonistic anti-CD74 antibody known in the art. 
     The anti-CD74 antibody may be selected such that it competes with or blocks binding to CD74 of an LL1 antibody comprising the light chain CDR sequences CDR1 (RSSQSLVHRNGNTYLH; SEQ ID NO:1), CDR2 (TVSNRFS; SEQ ID NO:2), and CDR3 (SQSSHVPPT; SEQ ID NO:3) and the heavy chain variable region CDR sequences CDR1 (NYGVN; SEQ ID NO:4), CDR2 (WINPNTGEPTFDDDFKG; SEQ ID NO:5), and CDR3 (SRGKNEAWFAY; SEQ ID NO:6). Alternatively, the anti-CD74 antibody may bind to the same epitope of CD74 as an LL1 antibody. 
     Many examples of anti-CD20 antibodies are known in the art and any such known antibody or fragment thereof may be utilized. In a preferred embodiment, the anti-CD20 antibody is an hA20 antibody (also known as veltuzumab) that comprises the light chain complementarity-determining region (CDR) sequences CDR1 (RASSSVSYIH; SEQ ID NO:7), CDR2 (ATSNLAS; SEQ ID NO:8), and CDR3 (QQWTSNPPT; SEQ ID NO:9) and the heavy chain variable region CDR sequences CDR1 (SYNMH; SEQ ID NO:10), CDR2 (AIYPGNGDTSYNQKFKG; SEQ ID NO:11), and CDR3 (STYYGGDWYFDV; SEQ ID NO:12). 
     A humanized anti-CD20 antibody suitable for use is disclosed in U.S. Pat. No. 7,435,803, incorporated herein by reference from Col. 36, line 4 through Col. 46, line 52 and  FIGS. 1, 2, 4, 5 and 7 . However, in alternative embodiments, other known and/or commercially available anti-CD20 antibodies may be utilized, such as rituximab; ofatumumab; ibritumomab; tositumomab; ocrelizumab; GA101; BCX-301; DXL 625; L26, B-Lyl, MEM-97, LT20, 2H7, AT80, B-H20 (ABCAM®, Cambridge, Mass.); HI20a, HI47, 13.6E12 (ABBIOTEC®, San Diego, Calif.); 4f11, 5c11, 7d1 (ABD SEROTEC®, Raleigh, N.C.) and any other anti-CD20 antibody known in the art. 
     The anti-CD20 antibody may be selected such that it competes with or blocks binding to CD20 of an hA20 antibody comprising the light chain complementarity-determining region (CDR) sequences CDR1 (RASSSVSYIH; SEQ ID NO:7), CDR2 (ATSNLAS; SEQ ID NO:8), and CDR3 (QQWTSNPPT; SEQ ID NO:9) and the heavy chain variable region CDR sequences CDR1 (SYNMH; SEQ ID NO:10), CDR2 (AIYPGNGDTSYNQKFKG; SEQ ID NO:11), and CDR3 (STYYGGDWYFDV; SEQ ID NO:12). Alternatively, the anti-CD20 antibody may bind to the same epitope of CD20 as a hA20 antibody. 
     Many examples of anti-CD22 antibodies are also known in the art and any such known antibody or fragment thereof may be utilized. In a preferred embodiment, the anti-CD22 antibody is an hLL2 antibody (also known as epratuzumab) that comprises the light chain CDR sequences CDR1 (KSSQSVLYSANHKYLA, SEQ ID NO:13), CDR2 (WASTRES, SEQ ID NO:14), and CDR3 (HQYLSSWTF, SEQ ID NO:15) and the heavy chain CDR sequences CDR1 (SYWLH, SEQ ID NO:16), CDR2 (YINPRNDYTEYNQNFKD, SEQ ID NO:17), and CDR3 (RDITTFY, SEQ ID NO:18). A humanized LL2 anti-CD22 antibody suitable for use is disclosed in U.S. Pat. No. 6,187,287, incorporated herein by reference from Col. 11, line 40 through Col. 20, line 38 and  FIGS. 1, 4 and 5 . However, in alternative embodiments, other known and/or commercially available anti-CD22 antibodies may be utilized, such as 1F5; HIB22 (ABBIOTEC®, San Diego, Calif.); FPC1, LT22, MEM-1, RFB4 (ABCAM®, Cambridge, Mass.); bu59, fpc1, mc64-12 (ABD SEROTEC®, Raleigh, N.C.); IS7 (ABNOVA®, Taipei City, Taiwan) and any other anti-CD22 antibody known in the art. 
     The anti-CD22 antibody may be selected such that it competes with or blocks binding to CD22 of an LL2 antibody comprising the light chain CDR sequences CDR1 (KSSQSVLYSANHKYLA, SEQ ID NO:13), CDR2 (WASTRES, SEQ ID NO:14), and CDR3 (HQYLSSWTF, SEQ ID NO:15) and the heavy chain CDR sequences CDR1 (SYWLH, SEQ ID NO:16), CDR2 (YINPRNDYTEYNQNFKD, SEQ ID NO:17), and CDR3 (RDITTFY, SEQ ID NO:18). Alternatively, the anti-CD22 antibody may bind to the same epitope of CD22 as an LL2 antibody. 
     Many examples of anti-HLA-DR antibodies are also known in the art and any such known antibody or fragment thereof may be utilized. In a preferred embodiment, the anti-HLA-DR antibody is an hL243 antibody (also known as IMMU-114) that comprises the heavy chain CDR sequences CDR1 (NYGMN, SEQ ID NO:19), CDR2 (WINTYTREPTYADDFKG, SEQ ID NO:20), and CDR3 (DITAVVPTGFDY, SEQ ID NO:21) and the light chain CDR sequences CDR1 (RASENIYSNLA, SEQ ID NO:22), CDR2 (AASNLAD, SEQ ID NO:23), and CDR3 (QHFWTTPWA, SEQ ID NO:24). A humanized L243 anti-HLA-DR antibody suitable for use is disclosed in U.S. Pat. No. 7,612,180, incorporated herein by reference from Col. 46, line 45 through Col. 60, line 50 and  FIG. 1  through  FIG. 6 . However, in alternative embodiments, other known and/or commercially available anti-HLA-DR antibodies may be utilized, such as 1D10 (apolizumab) (Kostelny et al., 2001, Int J Cancer 93:556-65); MS-GPC-1, MS-GPC-6, MS-GPC-8, MS-GPC-10, etc. (U.S. Pat. No. 7,521,047); Lym-1, TAL 8.1, 520B, ML11C11, SPM289, MEM-267, TAL 15.1, TAL 1B5, G-7, 4D12, Bra30 (Santa Cruz Biotechnology, Inc., Santa Cruz, Calif.); TAL 16.1, TU36, C120 (ABCAM®, Cambridge, Mass.); and any other anti-HLA-DR antibody known in the art. 
     The anti-HLA-DR antibody may be selected such that it competes with or blocks binding to HLA-DR of an L243 antibody comprising the heavy chain CDR sequences CDR1 (NYGMN, SEQ ID NO:19), CDR2 (WINTYTREPTYADDFKG, SEQ ID NO:20), and CDR3 (DITAVVPTGFDY, SEQ ID NO:21) and the light chain CDR sequences CDR1 (RASENIYSNLA, SEQ ID NO:22), CDR2 (AASNLAD, SEQ ID NO:23), and CDR3 (QHFWTTPWA, SEQ ID NO:24). Alternatively, the anti-HLA-DR antibody may bind to the same epitope of HLA-DR as an L243 antibody. 
     The anti-CD74 and/or other antibodies or fragments thereof may be used as naked antibodies, alone or in combination with one or more therapeutic agents. Alternatively, the antibodies or fragments may be utilized as immunoconjugates, attached to one or more therapeutic agents. (For methods of making immunoconjugates, see, e.g., U.S. Pat. Nos. 4,699,784; 4,824,659; 5,525,338; 5,677,427; 5,697,902; 5,716,595; 6,071,490; 6,187,284; 6,306,393; 6,548,275; 6,653,104; 6,962,702; 7,033,572; 7,147,856; and 7,259,240, the Examples section of each incorporated herein by reference.) Therapeutic agents may be selected from the group consisting of a radionuclide, a cytotoxin, a chemotherapeutic agent, a drug, a pro-drug, a toxin, an enzyme, an immunomodulator, an anti-angiogenic agent, a pro-apoptotic agent, a cytokine, a hormone, an oligonucleotide molecule (e.g., an antisense molecule or a gene) or a second antibody or fragment thereof. 
     The therapeutic agent may be selected from the group consisting of aplidin, azaribine, anastrozole, azacytidine, bleomycin, bortezomib, bryostatin-1, busulfan, calicheamycin, camptothecin, 10-hydroxycamptothecin, carmustine, celebrex, chlorambucil, cisplatin, irinotecan (CPT-11), SN-38, carboplatin, cladribine, cyclophosphamide, cytarabine, dacarbazine, docetaxel, dactinomycin, daunomycin glucuronide, daunorubicin, dexamethasone, diethylstilbestrol, doxorubicin, doxorubicin glucuronide, epirubicin glucuronide, ethinyl estradiol, estramustine, etoposide, etoposide glucuronide, etoposide phosphate, floxuridine (FUdR), 3′,5′-O-dioleoyl-FudR (FUdR-dO), fludarabine, flutamide, fluorouracil, fluoxymesterone, gemcitabine, hydroxyprogesterone caproate, hydroxyurea, idarubicin, ifosfamide, L-asparaginase, leucovorin, lomustine, mechlorethamine, medroprogesterone acetate, megestrol acetate, melphalan, mercaptopurine, 6-mercaptopurine, methotrexate, mitoxantrone, mithramycin, mitomycin, mitotane, phenyl butyrate, prednisone, procarbazine, paclitaxel, pentostatin, PSI-341, semustine streptozocin, tamoxifen, taxanes, taxol, testosterone propionate, thalidomide, thioguanine, thiotepa, teniposide, topotecan, uracil mustard, velcade, vinblastine, vinorelbine, vincristine, ricin, abrin, ribonuclease, onconase, rapLR1, DNase I, Staphylococcal enterotoxin-A, pokeweed antiviral protein, gelonin, diphtheria toxin,  Pseudomonas  exotoxin, and  Pseudomonas  endotoxin. 
     The therapeutic agent may comprise a radionuclide selected from the group consisting of  103m Rh,  103 Ru,  105 Rh,  105 Ru,  107 Hg,  109 Pd,  109 Pt,  111 Ag,  111 In,  113m In,  119 Sb,  11 C,  121m Te,  122m Te,  125 I,  125m Te,  126 I,  131 I,  133 I,  13 N,  142 Pr,  143 Pr,  149 Pm,  152 Dy,  153 Sm,  15 O,  161 Ho,  161 Tb,  165 Tm,  166 Dy,  166 Ho,  167 Tm,  168 Tm,  169 Er,  169 Yb,  177 Lu,  186 Re,  188 Re,  189m Os,  189 Re,  192 Ir,  194 Ir,  197 Pt,  198 Au,  199 Au,  201 Tl,  203 Hg,  211 At,  211 Bi,  211 Pb,  212 Bi,  212 Pb,  213 Bi,  215 Po,  217 At,  219 Rn,  221 Fr,  223 Ra,  224 Ac,  225 Ac,  225 Fm,  32 P,  33 P,  47 Sc,  51 Cr,  57 Co,  58 Co,  59 Fe,  62 Cu,  67 Cu,  67 Ga,  75 Br,  75 Se,  76 Br,  77 As,  77 Br,  80m Br,  89 Sr,  90 Y,  95 Ru,  97 Ru,  99 Mo and  99m Tc. 
     The therapeutic agent may be an enzyme selected from the group consisting of malate dehydrogenase, staphylococcal nuclease, delta-V-steroid isomerase, yeast alcohol dehydrogenase, alpha-glycerophosphate dehydrogenase, triose phosphate isomerase, horseradish peroxidase, alkaline phosphatase, asparaginase, glucose oxidase, beta-galactosidase, ribonuclease, urease, catalase, glucose-6-phosphate dehydrogenase, glucoamylase and acetylcholinesterase. 
     An immunomodulator of use may be selected from the group consisting of a cytokine, a stem cell growth factor, a lymphotoxin, a hematopoietic factor, a colony stimulating factor (CSF), an interferon (IFN), erythropoietin, thrombopoietin and combinations thereof. Exemplary immunomodulators may include IL-1, IL-2, IL-3, IL-6, IL-10, IL-12, IL-18, IL-21, interferon-α, interferon-β, interferon-γ, G-CSF, GM-CSF, and mixtures thereof. 
     Exemplary anti-angiogenic agents may include angiostatin, endostatin, baculostatin, canstatin, maspin, anti-VEGF binding molecules, anti-placental growth factor binding molecules, or anti-vascular growth factor binding molecules. 
     In certain embodiments, the antibody or fragment may comprise one or more chelating moieties, such as NOTA, DOTA, DTPA, TETA, Tscg-Cys, or Tsca-Cys. In certain embodiments, the chelating moiety may form a complex with a therapeutic or diagnostic cation, such as Group II, Group III, Group IV, Group V, transition, lanthanide or actinide metal cations, Tc, Re, Bi, Cu, As, Ag, Au, At, or Pb. 
     In some embodiments, the antibody or fragment thereof may be a human, chimeric, or humanized antibody or fragment thereof. A humanized antibody or fragment thereof may comprise the complementarity-determining regions (CDRs) of a murine antibody and the constant and framework (FR) region sequences of a human antibody, which may be substituted with at least one amino acid from corresponding FRs of a murine antibody. A chimeric antibody or fragment thereof may include the light and heavy chain variable regions of a murine antibody, attached to human antibody constant regions. The antibody or fragment thereof may include human constant regions of IgG1, IgG2a, IgG3, or IgG4. 
     Exemplary known antibodies of use include, but are not limited to, hR1 (anti-IGF-1R), hPAM4 (anti-mucin), hA20 (anti-CD20), hAl9 (anti-CD19), hIMMU31 (anti-AFP), hLL1 (anti-CD74), hLL2 (anti-CD22), hMu-9 (anti-CSAp), hL243 (anti-HLA-DR), hMN-14 (anti-CEACAM5), hMN-15 (anti-CEACAM6), 29H2 (anti-CEACAM1, ABCAM®), hRS7 (anti-EGP-1—also known as Trop-2), elsilimomab (anti-IL-6), ALD518 (anti-IL-6), alemtuzumab (anti-CD52), daclizumab (anti-CD25), galiximab (anti-CD80), adalimumab (anti-TNF-α), infliximab (anti-TNF-α), lucatumumab (anti-CD40), ofatumumab (anti-CD20) and hMN-3 (anti-CEACAM6). Antibodies against antigens of use include anti-CXCR4 (e.g., U.S. Pat. Nos. 7,138,496; 7,682,611; 7,521,045; 7,892,546) and IL-6 (e.g., U.S. Pat. Nos. 7,919,095; 7,935,340; 7,955,597), the Examples section of each cited patent incorporated herein by reference. 
     Although in preferred embodiments that antibodies or fragments thereof incorporated into the hexavalent constructs bind to CD74 and/or CD20, in alternative embodiments antibodies or fragments may bind to one or more target antigens selected from the group consisting of carbonic anhydrase IX, alpha-fetoprotein, α-actinin-4, A3, antigen specific for A33 antibody, ART-4, B7, Ba 733, BAGE, BrE3-antigen, CAl25, CAMEL, CAP-1, CASP-8/m, CCCL19, CCCL21, CD1, CD1a, CD2, CD3, CD4, CD5, CD8, CD11A, CD14, CD15, CD16, CD18, CD19, CD20, CD21, CD22, CD23, CD25, CD29, CD30, CD32b, CD33, CD37, CD38, CD40, CD40L, CD45, CD46, CD52, CD54, CD55, CD59, CD64, CD66a-e, CD67, CD70, CD74, CD79a, CD80, CD83, CD95, CD126, CD132, CD133, CD138, CD147, CD154, CDC27, CDK-4/m, CDKN2A, CXCR4, colon-specific antigen-p (CSAp), CEA (CEACAM5), CEACAM1, CEACAM6, c-met, DAM, EGFR, EGFRvIII, EGP-1, EGP-2, ELF2-M, Ep-CAM, Flt-1, Flt-3, folate receptor, G250 antigen, GAGE, gp100, GROB, HLA-DR, HM1.24, human chorionic gonadotropin (HCG) and its subunits, HER2/neu, HMGB-1, hypoxia inducible factor (HIF-1), HSP70-2M, HST-2, Ia, IGF-1R, IFN-γ, IFN-α, IFN-β, IL-2, IL-4R, IL-6R, IL-13R, IL-15R, IL-17R, IL-18R, IL-6, IL-8, IL-12, IL-15, IL-17, IL-18, IL-23, IL-25, insulin-like growth factor-1 (IGF-1), KC4-antigen, KS-1-antigen, KS1-4, Le-Y, LDR/FUT, macrophage migration inhibitory factor (MIF), MAGE, MAGE-3, MART-1, MART-2, NY-ESO-1, TRAG-3, mCRP, MCP-1, MIP-1A, MIP-1B, MIF, MUC1, MUC2, MUC3, MUC4, MUC5, MUM-1/2, MUM-3, NCA66, NCA95, NCA90, antigen specific for PAM-4 antibody, placental growth factor, p53, PLAGL2, prostatic acid phosphatase, PSA, PRAIVIE, PSMA, PlGF, IGF, IGF-1R, IL-6, RS5, RANTES, T101, SAGE, S100, survivin, survivin-2B, TAC, TAG-72, tenascin, TRAIL receptors, TNF-α, Tn antigen, Thomson-Friedenreich antigens, tumor necrosis antigens, VEGFR, ED-B fibronectin, WT-1, 17-1A-antigen, complement factors C3, C3a, C3b, C5a, C5, an angiogenesis marker, bcl-2, bcl-6, Kras, cMET, an oncogene marker and an oncogene product (see, e.g., Sensi et al., Clin Cancer Res 2006, 12:5023-32; Parmiani et al., J Immunol 2007, 178:1975-79; Novellino et al. Cancer Immunol Immunother 2005, 54:187-207). Reports on tumor associated antigens include Mizukami et al., (2005, Nature Med. 11:992-97); Hatfield et al., (2005, Curr. Cancer Drug Targets 5:229-48); Vallbohmer et al. (2005, J. Clin. Oncol. 23:3536-44); and Ren et al. (2005, Ann. Surg. 242:55-63). 
     Also disclosed is a method for treating and/or diagnosing a disease or disorder that includes administering to a patient a therapeutic and/or diagnostic composition that includes any of the aforementioned antibodies or fragments thereof. Typically, the composition is administered to the patient intravenously, intramuscularly or subcutaneously at a dose of 20-5000 mg. In preferred embodiments, the disease or disorder is a solid tumor that overexpresses CD74, a B-cell lymphoma or leukemia, an immune dysregulation disease, an autoimmune disease, organ-graft rejection or graft-versus-host disease. Exemplary malignancies that may be treated using the claimed methods and compositions include, but are not limited to, glioblastoma, gastric cancer, bladder cancer, prostate cancer, thymic cancer, colorectal cancer, lung cancer, renal cancer, pancreatic cancer, breast cancer, indolent forms of B-cell lymphomas, aggressive forms of B-cell lymphomas, acute lymphocytic leukemia, chronic lymphocytic leukemia, Hodgkin&#39;s lymphoma, non-Hodgkin&#39;s lymphoma, mantle cell lymphoma, diffuse large B-cell lymphoma, follicular lymphoma, marginal zone lymphoma, Burkitt&#39;s lymphoma and multiple myeloma. 
     Exemplary autoimmune diseases include acute immune thrombocytopenia, chronic immune thrombocytopenia, dermatomyositis, Sydenham&#39;s chorea, myasthenia gravis, systemic lupus erythematosus, lupus nephritis, rheumatic fever, polyglandular syndromes, bullous pemphigoid, pemphigus vulgaris, diabetes mellitus (e.g., juvenile diabetes), Henoch-Schonlein purpura, post-streptococcal nephritis, erythema nodosum, Takayasu&#39;s arteritis, Addison&#39;s disease, rheumatoid arthritis, multiple sclerosis, sarcoidosis, ulcerative colitis, erythema multiforme, IgA nephropathy, polyarteritis nodosa, ankylosing spondylitis, Goodpasture&#39;s syndrome, thromboangitis obliterans, Sjogren&#39;s syndrome, primary biliary cirrhosis, Hashimoto&#39;s thyroiditis, thyrotoxicosis, scleroderma, chronic active hepatitis, polymyositis/dermatomyositis, polychondritis, pemphigus vulgaris, Wegener&#39;s granulomatosis, membranous nephropathy, amyotrophic lateral sclerosis, tabes dorsalis, giant cell arteritis/polymyalgia, pernicious anemia, rapidly progressive glomerulonephritis, psoriasis, or fibrosing alveolitis. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following Figures are provided to illustrate exemplary, but non-limiting, preferred embodiments of the invention. 
         FIG. 1A . Direct cytotoxicity induced by anti-CD20/CD74 HexAbs in NHL cell lines as determined by the MTS assay. JeKo-1, Granta-519, Mino, and Raji (5×10 4  cells per well in 48-well plate) treated with indicated concentrations of antibodies for 4 days. 
         FIG. 1B . Direct cytotoxicity induced by anti-CD20/CD74 HexAbs in NHL cell lines as determined by the MTS assay. Effect of monospecific 20-(20)-(20) on JeKo-1, Granta-519 and Mino; bispecific 20-(22)-(22) on JeKo-1; and monospecific 74-(74)-(74) on Raji. 
         FIG. 1C . Direct cytotoxicity induced by anti-CD20/CD74 HexAbs in NHL cell lines as determined by the MTS assay. Dose-response curves showing partial inhibition of 20-(74)-(74) and 74-(20)-(20) in JeKo-1 by excess hA20 or hLL1 (10 μg/ml). 
         FIG. 2A . Induction of apoptosis by anti-CD20/CD74 HexAbs. JeKo-1 cells (2×10 5  cells per well in 6-well plate) were treated with 10 nM of indicated antibodies for 48 h followed by annexin staining analysis. The two bispecific anti-CD20/CD74 HexAbs induced statistically significant apoptosis in JeKo-1 cells compared to cells treated or not treated with parental antibodies, alone or combined (P&lt;0.033). 
         FIG. 2B . Induction of apoptosis by anti-CD20/CD74 HexAbs. Annexin analysis on primary samples from MCL patients treated with indicated antibodies (10 nM) for 24 to 48 h. Data are shown as Annexin + PI −  cells (early apoptosis). The two anti-CD20/CD74 HexAbs induced statistically significant early apoptosis in MCL (P&lt;0.008) compared to the untreated controls. 
         FIG. 2C . Induction of apoptosis by anti-CD20/CD74 HexAbs. Annexin analysis on primary samples from CLL patients treated with indicated antibodies (10 nM) for 24 to 48 h. Data are shown as Annexin + PI −  cells (early apoptosis). The two anti-CD20/CD74 HexAbs induced statistically significant early apoptosis in CLL (P&lt;0.03) compared to the untreated controls. One of the patient samples (CLL 216) did not respond to any treatment. 
         FIG. 2D . Induction of apoptosis by anti-CD20/CD74 HexAbs. Both anti-CD20/CD74 HexAbs induced changes in mitochondrial membrane potential (upper panel) and generated ROS (lower panel) in Granta-519. 
         FIG. 3A . Correlation of homotypic adhesion, actin reorganization, and lysosomal involvement to cell death evoked by the bispecific anti-CD20/CD74 HexAbs. Apoptosis induced by HexAbs was reduced significantly (P&lt;0.025) in Jeko-1 with 2 μM of cytochalasin D (CsD), another inhibitor of actin polymerization. 
         FIG. 3B . Correlation of homotypic adhesion, actin reorganization, and lysosomal involvement to cell death evoked by the bispecific anti-CD20/CD74 HexAbs. Lysosomal V ATPase inhibitors, concanamycin A (Con A) and bafilomycin A1 (Bfa1), inhibited the apoptosis induced by HexAbs in JeKo-1 cells. 
         FIG. 4A . Activity of HexAbs in human blood ex vivo. 20-(74)-(74) and 74-(20)-(20), tested at 10 and 25 nM in JeKo-1 (upper panel) and normal B cells (lower panel). 
         FIG. 4B . Activity of HexAbs in human blood ex vivo. 20-(74)-(74) tested at 0.1, 0.5 and 1 nM in Jeko-1 (upper panel) and normal B cells (lower panel). The effect of the indicated antibodies on the growth of spiked JeKo-1 cells in whole blood from a healthy volunteer was determined after 48 h. JeKo-1 cells were analyzed as CD19+ events in the monocyte gate. B cells were analyzed as CD19+ events in the lymphocyte gate. Error bars represent SD. 
         FIG. 5 . Therapeutic efficacy of HexAbs in disseminated JeKo-1 xenograft model. Seven groups of 8 mice (8-wk-old female SCID mice) each were inoculated i.v. with JeKo-1 (2.5×10 7  cells per animal). After 7 days, three different does (i.e., 370 μg, 37 μs and 3.7 μs) of both HexAbs were administered via i.p. injections twice a week for two weeks. Control mice received saline injections. 74-(20)-(20) and 20-(74)-(74), at the 370 μg dose level, resulted in 30% and 60% increases in median survival compared to saline controls, respectively. 
         FIG. 6 . 20-(74)-(74) Induced potent ADCC in JeKo-1 cells. 
         FIG. 7 . Anti-CD74 antibody (milatuzumab) increases the cytotoxicity of rituximab. The Figure shows the percent of untreated control values in MTT cytotoxicity assays. Cells were incubated with the antibodies for 4 days in the presence of goat anti-human IgG as a crosslinker. The Figure shows several lines of NHL (left side), CLL (center) and ALL (right side) cell lines. 
         FIG. 8 . Anti-CD74 antibody (milatuzumab) increases the cytotoxicity of fludarabine. The Figure shows the percent of untreated control values in MTS cytotoxicity assays. Cells were incubated with fludarabine and milatuzumab for 4 days in the presence of goat anti-human IgG as a crosslinker. The Figure shows the effects on NHL (left side) and CLL (right side) cell lines. 
     
    
    
     DETAILED DESCRIPTION 
     Definitions 
     As used herein, the terms “a”, “an” and “the” may refer to either the singular or plural, unless the context otherwise makes clear that only the singular is meant. 
     An “antibody” refers to a full-length (i.e., naturally occurring or formed by normal immunoglobulin gene fragment recombinatorial processes) immunoglobulin molecule (e.g., an IgG antibody) or an immunologically active (i.e., antigen-binding) portion of an immunoglobulin molecule, like an antibody fragment. 
     An “antibody fragment” is a portion of an antibody such as F(ab′) 2 , F(ab) 2 , Fab′, Fab, Fv, scFv, single domain antibodies (DABs or VHHs) and the like, including half-molecules of IgG4 (van der Neut Kolfschoten et al. (Science 2007; 317(14 September):1554-1557). Regardless of structure, an antibody fragment binds with the same antigen that is recognized by the intact antibody. For example, an anti-CD74 antibody fragment binds with an epitope of CD74. The term “antibody fragment” also includes isolated fragments consisting of the variable regions, such as the “Fv” fragments consisting of the variable regions of the heavy and light chains and recombinant single chain polypeptide molecules in which light and heavy chain variable regions are connected by a peptide linker (“scFv proteins”). As used herein, the term “antibody fragment” does not include fragments such as Fc fragments that do not contain antigen-binding sites. 
     A “chimeric antibody” is a recombinant protein that contains the variable domains including the complementarity determining regions (CDRs) of an antibody derived from one species, preferably a rodent antibody, while the constant domains of the antibody molecule are derived from those of a human antibody. For veterinary applications, the constant domains of the chimeric antibody may be derived from that of other species, such as a cat or dog. 
     A “humanized antibody” is a recombinant protein in which the CDRs from an antibody from one species; e.g., a rodent antibody, are transferred from the heavy and light variable chains of the rodent antibody into human heavy and light variable domains. Additional FR amino acid substitutions from the parent, e.g. murine, antibody may be made. The constant domains of the antibody molecule are derived from those of a human antibody. 
     A “human antibody” is, for example, an antibody obtained from transgenic mice that have been genetically engineered to produce human antibodies in response to antigenic challenge. In this technique, elements of the human heavy and light chain locus are introduced into strains of mice derived from embryonic stem cell lines that contain targeted disruptions of the endogenous heavy chain and light chain loci. The transgenic mice can synthesize human antibodies specific for human antigens, and the mice can be used to produce human antibody-secreting hybridomas. Methods for obtaining human antibodies from transgenic mice are described by Green et al., Nature Genet. 7:13 (1994), Lonberg et al., Nature 368:856 (1994), and Taylor et al., Int. Immun. 6:579 (1994). A fully human antibody also can be constructed by genetic or chromosomal transfection methods, as well as phage display technology, all of which are known in the art. (See, e.g., McCafferty et al., Nature 348:552-553 (1990) for the production of human antibodies and fragments thereof in vitro, from immunoglobulin variable domain gene repertoires from unimmunized donors). In this technique, antibody variable domain genes are cloned in-frame into either a major or minor coat protein gene of a filamentous bacteriophage, and displayed as functional antibody fragments on the surface of the phage particle. Because the filamentous particle contains a single-stranded DNA copy of the phage genome, selections based on the functional properties of the antibody also result in selection of the gene encoding the antibody exhibiting those properties. In this way, the phage mimics some of the properties of the B cell. Phage display can be performed in a variety of formats, for their review, see, e.g. Johnson and Chiswell, Current Opinion in Structural Biology 3:5564-571 (1993). Human antibodies may also be generated by in vitro activated B cells. (See, U.S. Pat. Nos. 5,567,610 and 5,229,275). 
     A “therapeutic agent” is an atom, molecule, or compound that is useful in the treatment of a disease. Examples of therapeutic agents include but are not limited to antibodies, antibody fragments, drugs, toxins, enzymes, nucleases, hormones, immunomodulators, antisense oligonucleotides, chelators, boron compounds, photoactive agents, dyes and radioisotopes. 
     A “diagnostic agent” is an atom, molecule, or compound that is useful in diagnosing a disease. Useful diagnostic agents include, but are not limited to, radioisotopes, dyes, contrast agents, fluorescent compounds or molecules and enhancing agents (e.g., paramagnetic ions). Preferably, the diagnostic agents are selected from the group consisting of radioisotopes, enhancing agents, and fluorescent compounds. 
     An “immunoconjugate” is a conjugate of an antibody, antibody fragment, antibody fusion protein, bispecific antibody or multispecific antibody with an atom, molecule, or a higher-ordered structure (e.g., with a carrier, a therapeutic agent, or a diagnostic agent). A “naked antibody” is an antibody that is not conjugated to any other agent. 
     As used herein, the term “antibody fusion protein” is a recombinantly produced antigen-binding molecule in which an antibody or antibody fragment is covalently linked to another protein or peptide, such as the same or different antibody or antibody fragment or a DDD or AD peptide. The fusion protein may comprise a single antibody component, a multivalent or multispecific combination of different antibody components or multiple copies of the same antibody component. The fusion protein may additionally comprise an antibody or an antibody fragment and a therapeutic agent. Examples of therapeutic agents suitable for such fusion proteins include immunomodulators and toxins. One preferred toxin comprises a ribonuclease (RNase), preferably a recombinant RNase. 
     A “multispecific antibody” is an antibody that can bind simultaneously to at least two targets that are of different structure, e.g., two different antigens, two different epitopes on the same antigen, or a hapten and/or an antigen or epitope. A “multivalent antibody” is an antibody that can bind simultaneously to at least two targets that are of the same or different structure. Valency indicates how many binding arms or sites the antibody has to a single antigen or epitope; i.e., monovalent, bivalent, trivalent or multivalent. The multivalency of the antibody means that it can take advantage of multiple interactions in binding to an antigen, thus increasing the avidity of binding to the antigen. Specificity indicates how many antigens or epitopes an antibody is able to bind; i.e., monospecific, bispecific, trispecific, multispecific. Using these definitions, a natural antibody, e.g., an IgG, is bivalent because it has two binding arms but is monospecific because it binds to one epitope. Multispecific, multivalent antibodies are constructs that have more than one binding site of different specificity. For example, a diabody, where one binding site reacts with one antigen and the other with another antigen. 
     A “bispecific antibody” is an antibody that can bind simultaneously to two targets which are of different structure. 
     CD74 
     CD74 (also known as invariant chain or Ii) is a transmembrane glycoprotein that associates with MHC class II α and β chains and directs transport of αβIi complexes to endosomes and lysosomes. CD74 functions as a molecular chaperone in the processing of exogenous peptides for antigen presentation via MHC class II. More recently, CD74 has been identified as the endogenous receptor for MIF (macrophage migration inhibitory factor), a key regulatory molecule that promotes cell survival and inhibits apoptosis by activation of the Akt pathway (Lue et al., Oncogene 207, 26:5046-59). As such, the interaction of CD74 and MIF is thought to play a significant role in tumorigenesis and tumor progression (Id.) 
     CD74 is overexpressed in a variety of disease states, including many solid and hematopoietic tumors (Stein et al., Clin Cancer Res 2007, 13:5556s-63s; Gold et al., Int J Clin Exp Pathol 2011, 4:1-12). Milatuzumab (hLL1), a humanized anti-CD74 antibody, is rapidly internalized into CD74 expressing cells and has been used to target therapeutic agents to tumor cells, with excellent therapeutic effects (see, e.g., Griffiths et al., Clin Cancer Res 2003, 9:6567-71; Ochaskovskaya et al., Clin Cancer Res 2001, 7:1505-10). However, naked milatuzumab has also been shown to be cytotoxic in the presence of cross-linking antibodies (e.g., U.S. Pat. No. 7,312,318). Combinations of milatuzumab with other therapeutic agents show enhanced cytotoxicity and improved therapeutic response in multiple myeloma cell lines (Stein et al., Clin Cancer Res 2009, 15:2808-17). 
     Milatuzumab has been reported to be efficacious for a wide range of hematopoietic malignancies, including non-Hodgkin&#39;s lymphoma, Burkitt lymphoma, follicular lymphoma, multiple myeloma, chronic lymphocytic leukemia and mantle cell lymphoma (Stein et al., Clin Cancer Res 2007, 13:5556s-63s; Berkova et al., Expert Opin. Invest. Drugs 2010, 19:141-49). Since CD74 is also over-expressed in a number of solid tumors, use of milatuzumab or other anti-CD74 antibodies for therapy of colorectal carcinoma, pancreatic carcinoma, gastric carcinoma, non-small cell lung carcinoma, glioblastoma, thymic carcinoma, pancreatic cancer, breast cancer, bladder cancer and prostate cancer has also been suggested (Gold et al., Int J Clin Exp Pathol 2011, 4:1-12; Berkova et al., Expert Opin. Invest. Drugs 2010, 19:141-49). Therapy directed to CD74 has been indicated in autoimmune or immune dysfunction diseases, such as systemic lupus erythematosus and rheumatoid arthritis (Lapter et al., Immunology 2011, 1327-95; Morand and Leech, Front Biosci 2005, 10:12-22). Combination therapy, such as with anti-CD74/anti-CD20 antibodies, has been reported to show improved efficacy in mantle cell lymphoma (Alinari et al., Blood 2011, 117:4530-41). 
     The skilled artisan will realize that these therapeutic effects are not limited to milatuzumab, but may also be seen with other anti-CD74 antibodies, particularly those that compete with milatuzumab for binding or that bind to the same epitope of CD74 as milatuzumab. 
     Dock-and-Lock (DNL) 
     In preferred embodiments, multivalent monospecific or bispecific antibodies may be produced using the dock-and-lock (DNL) technology (see, e.g., U.S. Pat. Nos. 7,521,056; 7,550,143; 7,534,866; 7,527,787 and 7,666,400; the Examples section of each of which is incorporated herein by reference). The DNL method exploits specific protein/protein interactions that occur between the regulatory (R) subunits of cAMP-dependent protein kinase (PKA) and the anchoring domain (AD) of A-kinase anchoring proteins (AKAPs) (Baillie et al., FEBS Letters. 2005; 579: 3264. Wong and Scott, Nat. Rev. Mol. Cell Biol. 2004; 5: 959). PKA, which plays a central role in one of the best studied signal transduction pathways triggered by the binding of the second messenger cAMP to the R subunits, was first isolated from rabbit skeletal muscle in 1968 (Walsh et al., J. Biol. Chem. 1968; 243:3763). The structure of the holoenzyme consists of two catalytic subunits held in an inactive form by the R subunits (Taylor, J. Biol. Chem. 1989; 264:8443). Isozymes of PKA are found with two types of R subunits (RI and RII), and each type has α and β isoforms (Scott, Pharmacol. Ther. 1991; 50:123). Thus, there are four types of PKA regulatory subunits—RIα, RIβ, RIIα and RIIβ. The R subunits have been isolated only as stable dimers and the dimerization domain has been shown to consist of the first 44 amino-terminal residues (Newlon et al., Nat. Struct. Biol. 1999; 6:222). Binding of cAMP to the R subunits leads to the release of active catalytic subunits for a broad spectrum of serine/threonine kinase activities, which are oriented toward selected substrates through the compartmentalization of PKA via its docking with AKAPs (Scott et al., J. Biol. Chem. 1990; 265; 21561). 
     Since the first AKAP, microtubule-associated protein-2, was characterized in 1984 (Lohmann et al., Proc. Natl. Acad. Sci USA. 1984; 81:6723), more than 50 AKAPs that localize to various sub-cellular sites, including plasma membrane, actin cytoskeleton, nucleus, mitochondria, and endoplasmic reticulum, have been identified with diverse structures in species ranging from yeast to humans (Wong and Scott, Nat. Rev. Mol. Cell Biol. 2004; 5:959). The AD of AKAPs for PKA is an amphipathic helix of 14-18 residues (Carr et al., J. Biol. Chem. 1991; 266:14188). The amino acid sequences of the AD are quite varied among individual AKAPs, with the binding affinities reported for RII dimers ranging from 2 to 90 nM (Alto et al., Proc. Natl. Acad. Sci. USA. 2003; 100:4445). AKAPs will only bind to dimeric R subunits. For human RIIα, the AD binds to a hydrophobic surface formed by the 23 amino-terminal residues (Colledge and Scott, Trends Cell Biol. 1999; 6:216). Thus, the dimerization domain and AKAP binding domain of human RIIα are both located within the same N-terminal 44 amino acid sequence (Newlon et al., Nat. Struct. Biol. 1999; 6:222; Newlon et al., EMBO J. 2001; 20:1651), which is termed the DDD herein. 
     We have developed a platform technology to utilize the DDD of human PKA regulatory subunit and the AD of AKAP as an excellent pair of linker modules for docking any two entities, referred to hereafter as A and B, into a noncovalent complex, which could be further locked into a stably tethered structure through the introduction of cysteine residues into both the DDD and AD at strategic positions to facilitate the formation of disulfide bonds. The general methodology of the “dock-and-lock” approach is as follows. Entity A is constructed by linking a DDD sequence to a precursor of A, resulting in a first component hereafter referred to as a. Because the DDD sequence would effect the spontaneous formation of a dimer, A would thus be composed of a 3 . Entity B is constructed by linking an AD sequence to a precursor of B, resulting in a second component hereafter referred to as b. The dimeric motif of DDD contained in a 2  will create a docking site for binding to the AD sequence contained in b, thus facilitating a ready association of a 2  and b to form a binary, trimeric complex composed of a 2 b. This binding event is made irreversible with a subsequent reaction to covalently secure the two entities via disulfide bridges, which occurs very efficiently based on the principle of effective local concentration because the initial binding interactions should bring the reactive thiol groups placed onto both the DDD and AD into proximity (Chmura et al., Proc. Natl. Acad. Sci. USA. 2001; 98:8480) to ligate site-specifically. Using various combinations of linkers, adaptor modules and precursors, a wide variety of DNL constructs of different stoichiometry may be produced and used, including but not limited to dimeric, trimeric, tetrameric, pentameric and hexameric DNL constructs (see, e.g., U.S. Pat. Nos. 7,550,143; 7,521,056; 7,534,866; 7,527,787 and 7,666,400.) 
     By attaching the DDD and AD away from the functional groups of the two precursors, such site-specific ligations are also expected to preserve the original activities of the two precursors. This approach is modular in nature and potentially can be applied to link, site-specifically and covalently, a wide range of substances, including peptides, proteins, antibodies, antibody fragments, and other effector moieties with a wide range of activities. Utilizing the fusion protein method of constructing AD and DDD conjugated effectors described in the Examples below, virtually any protein or peptide may be incorporated into a DNL construct. However, the technique is not limiting and other methods of conjugation may be utilized. 
     A variety of methods are known for making fusion proteins, including nucleic acid synthesis, hybridization and/or amplification to produce a synthetic double-stranded nucleic acid encoding a fusion protein of interest. Such double-stranded nucleic acids may be inserted into expression vectors for fusion protein production by standard molecular biology techniques (see, e.g. Sambrook et al., Molecular Cloning, A laboratory manual, 2 nd  Ed, 1989). In such preferred embodiments, the AD and/or DDD moiety may be attached to either the N-terminal or C-terminal end of an effector protein or peptide. However, the skilled artisan will realize that the site of attachment of an AD or DDD moiety to an effector moiety may vary, depending on the chemical nature of the effector moiety and the part(s) of the effector moiety involved in its physiological activity. Site-specific attachment of a variety of effector moieties may be performed using techniques known in the art, such as the use of bivalent cross-linking reagents and/or other chemical conjugation techniques. 
     The skilled artisan will realize that the DNL technique may be utilized to produce complexes comprising multiple copies of the same anti-CD74 or anti-CD20 antibodies, or to attach one or more anti-CD74 antibodies to one or more anti-CD20 antibodies or an antibody against a different target antigen expressed by B-cells. Alternatively, the DNL technique may be used to attach antibodies to different effector moieties, such as toxins, cytokines, carrier proteins for siRNA and other known effectors. 
     Structure-Function Relationships in AD and DDD Moieties 
     For different types of DNL constructs, different AD or DDD sequences may be utilized. Exemplary DDD and AD sequences are provided below. 
     
       
         
           
               
               
            
               
                   
                 DDD1 
               
               
                   
                 (SEQ ID NO: 25) 
               
               
                   
                 SHIQIPPGLTELLQGYTVEVLRQQPPDLVEFAVEYFTRLREARA 
               
               
                   
                   
               
               
                   
                 DDD2 
               
               
                   
                 (SEQ ID NO: 26) 
               
               
                   
                 CGHIQIPPGLTELLQGYTVEVLRQQPPDLVEFAVEYFTRLREARA 
               
               
                   
                   
               
               
                   
                 AD1 
               
               
                   
                 (SEQ ID NO: 27) 
               
               
                   
                 QIEYLAKQIVDNAIQQA 
               
               
                   
                   
               
               
                   
                 AD2 
               
               
                   
                 (SEQ ID NO: 28) 
               
               
                   
                 CGQIEYLAKQIVDNAIQQAGC 
               
            
           
         
       
     
     The skilled artisan will realize that DDD1 and DDD2 are based on the DDD sequence of the human RIIα isoform of protein kinase A. However, in alternative embodiments, the DDD and AD moieties may be based on the DDD sequence of the human RIα form of protein kinase A and a corresponding AKAP sequence, as exemplified in DDD3, DDD3C and AD3 below. 
     
       
         
           
               
            
               
                 DDD3 
               
               
                 (SEQ ID NO: 29) 
               
               
                 SLRECELYVQKHNIQALLKDSIVQLCTARPERPMAFLREYFERLEKEEAK 
               
               
                   
               
               
                 DDD3C 
               
               
                 (SEQ ID NO: 30) 
               
               
                 MSCGGSLRECELYVQKHNIQALLKDSIVQLCTARPERPMAFLREYFERLE 
               
               
                   
               
               
                 KEEAK 
               
               
                   
               
               
                 AD3 
               
               
                 (SEQ ID NO: 31) 
               
               
                 CGFEELAWKIAKMIWSDVFQQGC 
               
            
           
         
       
     
     In other alternative embodiments, other sequence variants of AD and/or DDD moieties may be utilized in construction of the DNL complexes. For example, there are only four variants of human PKA DDD sequences, corresponding to the DDD moieties of PKA RIα, RIIα, RIβ and RIIβ. The RIIα DDD sequence is the basis of DDD1 and DDD2 disclosed above. The four human PKA DDD sequences are shown below. The DDD sequence represents residues 1-44 of RIIα, 1-44 of RIIβ, 12-61 of RIα and 13-66 of RIβ. (Note that the sequence of DDD1 is modified slightly from the human PKA RIIα DDD moiety.) 
     
       
         
           
               
            
               
                 PKA RIα 
               
               
                 (SEQ ID NO: 32) 
               
               
                 SLRECELYVQKHNIQALLKDVSIVQLCTARPERPMAFLREYFEKLEKEEA 
               
               
                   
               
               
                 K 
               
               
                   
               
               
                 PKA RIβ 
               
               
                 (SEQ ID NO: 33) 
               
               
                 SLKGCELYVQLHGIQQVLKDCIVHLCISKPERPMKFLREHFEKLEKEENR 
               
               
                   
               
               
                 QILA 
               
               
                   
               
               
                 PKA RIIα 
               
               
                 (SEQ ID NO: 34) 
               
               
                 SHIQIPPGLTELLQGYTVEVGQQPPDLVDFAVEYFTRLREARRQ 
               
               
                   
               
               
                 PKA RIIβ 
               
               
                 (SEQ ID NO: 35) 
               
               
                 SIEIPAGLTELLQGFTVEVLRHQPADLLEFALQHFTRLQQENER 
               
            
           
         
       
     
     The structure-function relationships of the AD and DDD domains have been the subject of investigation. (See, e.g., Burns-Hamuro et al., 2005, Protein Sci 14:2982-92; Carr et al., 2001, J Biol Chem 276:17332-38; Alto et al., 2003, Proc Natl Acad Sci USA 100:4445-50; Hundsrucker et al., 2006, Biochem J 396:297-306; Stokka et al., 2006, Biochem J 400:493-99; Gold et al., 2006, Mol Cell 24:383-95; Kinderman et al., 2006, Mol Cell 24:397-408, the entire text of each of which is incorporated herein by reference.) 
     For example, Kinderman et al. (2006, Mol Cell 24:397-408) examined the crystal structure of the AD-DDD binding interaction and concluded that the human DDD sequence contained a number of conserved amino acid residues that were important in either dimer formation or AKAP binding, underlined in SEQ ID NO:25 below. (See FIG. 1 of Kinderman et al., 2006, incorporated herein by reference.) The skilled artisan will realize that in designing sequence variants of the DDD sequence, one would desirably avoid changing any of the underlined residues, while conservative amino acid substitutions might be made for residues that are less critical for dimerization and AKAP binding. 
     
       
         
           
               
               
            
               
                   
                 (SEQ ID NO: 25) 
               
               
                   
                 SH I Q I PPG L TE LL QG Y T V E VL RQQPPD LV E F A V E YF TR L REARA 
               
            
           
         
       
     
     As discussed in more detail below, conservative amino acid substitutions have been characterized for each of the twenty common L-amino acids. Thus, based on the data of Kinderman (2006) and conservative amino acid substitutions, potential alternative DDD sequences based on SEQ ID NO:25 are shown in Table 1. In devising Table 1, only highly conservative amino acid substitutions were considered. For example, charged residues were only substituted for residues of the same charge, residues with small side chains were substituted with residues of similar size, hydroxyl side chains were only substituted with other hydroxyls, etc. Because of the unique effect of proline on amino acid secondary structure, no other residues were substituted for proline. Even with such conservative substitutions, there are over twenty million possible alternative sequences for the 44 residue peptide (2×3×2×2×2×2×2×2×2×2×2×2×2×2×2×4×2×2×2×2×2×4×2×4). A limited number of such potential alternative DDD moiety sequences are shown in SEQ ID NO:36 to SEQ ID NO:55 below. The skilled artisan will realize that an almost unlimited number of alternative species within the genus of DDD moieties can be constructed by standard techniques, for example using a commercial peptide synthesizer or well known site-directed mutagenesis techniques. The effect of the amino acid substitutions on AD moiety binding may also be readily determined by standard binding assays, for example as disclosed in Alto et al. (2003, Proc Natl Acad Sci USA 100:4445-50). 
     
       
         
           
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Conservative Amino Acid Substitutions in DDD1 (SEQ ID NO: 25). 
               
               
                 Consensus sequence disclosed as SEQ ID NO: 141. 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 
                   S 
                 
                 
                   H 
                 
                 
                   
                     I 
                   
                 
                 
                   Q 
                 
                 
                   
                     I 
                   
                 
                 
                   P 
                 
                 
                   P 
                 
                 
                   G 
                 
                 
                   
                     L 
                   
                 
                 
                   T 
                 
                 
                   E 
                 
                 
                   
                     L 
                   
                 
                 
                   
                     L 
                   
                 
                 
                   Q 
                 
                 
                   G 
                 
                 
                   
                     Y 
                   
                 
                 
                   T 
                 
                 
                   
                     V 
                   
                 
                 
                   E 
                 
                 
                   
                     V 
                   
                 
                 
                   
                     L 
                   
                 
                 
                   R 
                 
               
               
                   
               
               
                 T 
                 K 
                   
                 N 
                   
                   
                   
                 A 
                   
                 S 
                 D 
                   
                   
                 N 
                 A 
                   
                 S 
                   
                 D 
                   
                   
                 K 
               
               
                   
                 R 
               
               
                   
               
               
                 
                   Q 
                 
                 
                   Q 
                 
                 
                   P 
                 
                 
                   P 
                 
                 
                   D 
                 
                 
                   
                     L 
                   
                 
                 
                   
                     V 
                   
                 
                 
                   E 
                 
                 
                   
                     F 
                   
                 
                 
                   A 
                 
                 
                   
                     V 
                   
                 
                 
                   E 
                 
                 
                   
                     Y 
                   
                 
                 
                   
                     F 
                   
                 
                 
                   T 
                 
                 
                   R 
                 
                 
                   
                     L 
                   
                 
                 
                   R 
                 
                 
                   E 
                 
                 
                   A 
                 
                 
                   R 
                 
                 
                   A 
                 
               
               
                   
               
               
                 N 
                 N 
                   
                   
                 E 
                   
                   
                 D 
                   
                 L 
                   
                 D 
                   
                   
                 S 
                 K 
                   
                 K 
                 D 
                 L 
                 K 
                 L 
               
               
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 I 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 I 
                   
                 I 
               
               
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 V 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 V 
                   
                 V 
               
               
                   
               
            
           
           
               
            
               
                 THIQIPPGLTELLQGYTVEVLRQQPPDLVEFAVEYFTRLREARA (SEQ ID NO: 36) 
               
               
                 SKIQIPPGLTELLQGYTVEVLRQQPPDLVEFAVEYFTRLREARA (SEQ ID NO: 37) 
               
               
                 SRIQIPPGLTELLQGYTVEVLRQQPPDLVEFAVEYFTRLREARA (SEQ ID NO: 38) 
               
               
                 SHINIPPGLTELLQGYTVEVLRQQPPDLVEFAVEYFTRLREARA (SEQ ID NO: 39) 
               
               
                 SHIQIPPALTELLQGYTVEVLRQQPPDLVEFAVEYFTRLREARA (SEQ ID NO: 40) 
               
               
                 SHIQIPPGLSELLQGYTVEVLRQQPPDLVEFAVEYFTRLREARA (SEQ ID NO: 41) 
               
               
                 SHIQIPPGLTDLLQGYTVEVLRQQPPDLVEFAVEYFTRLREARA (SEQ ID NO: 42) 
               
               
                 SHIQIPPGLTELLNGYTVEVLRQQPPDLVEFAVEYFTRLREARA (SEQ ID NO: 43) 
               
               
                 SHIQIPPGLTELLQAYTVEVLRQQPPDLVEFAVEYFTRLREARA (SEQ ID NO: 44) 
               
               
                 SHIQIPPGLTELLQGYSVEVLRQQPPDLVEFAVEYFTRLREARA (SEQ ID NO: 45) 
               
               
                 SHIQIPPGLTELLQGYTVDVLRQQPPDLVEFAVEYFTRLREARA (SEQ ID NO: 46) 
               
               
                 SHIQIPPGLTELLQGYTVEVLKQQPPDLVEFAVEYFTRLREARA (SEQ ID NO: 47) 
               
               
                 SHIQIPPGLTELLQGYTVEVLRNQPPDLVEFAVEYFTRLREARA (SEQ ID NO: 48) 
               
               
                 SHIQIPPGLTELLQGYTVEVLRQNPPDLVEFAVEYFTRLREARA (SEQ ID NO: 49) 
               
               
                 SHIQIPPGLTELLQGYTVEVLRQQPPELVEFAVEYFTRLREARA (SEQ ID NO: 50) 
               
               
                 SHIQIPPGLTELLQGYTVEVLRQQPPDLVDFAVEYFTRLREARA (SEQ ID NO: 51) 
               
               
                 SHIQIPPGLTELLQGYTVEVLRQQPPDLVEFLVEYFTRLREARA (SEQ ID NO: 52) 
               
               
                 SHIQIPPGLTELLQGYTVEVLRQQPPDLVEFIVEYFTRLREARA (SEQ ID NO: 53) 
               
               
                 SHIQIPPGLTELLQGYTVEVLRQQPPDLVEFVVEYFTRLREARA (SEQ ID NO: 54) 
               
               
                 SHIQIPPGLTELLQGYTVEVLRQQPPDLVEFAVDYFTRLREARA (SEQ ID NO: 55) 
               
               
                   
               
            
           
         
       
     
     Alto et al. (2003, Proc Natl Acad Sci USA 100:4445-50) performed a bioinformatic analysis of the AD sequence of various AKAP proteins to design an RII selective AD sequence called AKAP-IS (SEQ ID NO:27), with a binding constant for DDD of 0.4 nM. The AKAP-IS sequence was designed as a peptide antagonist of AKAP binding to PKA. Residues in the AKAP-IS sequence where substitutions tended to decrease binding to DDD are underlined in SEQ ID NO:27 below. The skilled artisan will realize that in designing sequence variants of the AD sequence, one would desirably avoid changing any of the underlined residues, while conservative amino acid substitutions might be made for residues that are less critical for DDD binding. Table 2 shows potential conservative amino acid substitutions in the sequence of AKAP-IS (AD1, SEQ ID NO:27), similar to that shown for DDD1 (SEQ ID NO:25) in Table 1 above. 
     Even with such conservative substitutions, there are over thirty-five thousand possible alternative sequences for the 17 residue AD1 (SEQ ID NO:27) peptide sequence (2×3×2×4×3×2×2×2×2×2×2×4). A limited number of such potential alternative AD moiety sequences are shown in SEQ ID NO:56 to SEQ ID NO:73 below. Again, a very large number of species within the genus of possible AD moiety sequences could be made, tested and used by the skilled artisan, based on the data of Alto et al. (2003). It is noted that FIG. 2 of Alto (2003) shows an even large number of potential amino acid substitutions that may be made, while retaining binding activity to DDD moieties, based on actual binding experiments. 
     
       
         
           
               
               
            
               
                   
                 AKAP-IS 
               
               
                   
                 (SEQ ID NO: 27) 
               
               
                   
                 QIEYL A KQ IV DN AI QQA  
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 Conservative Amino Acid Substitutions in AD1 
               
               
                 (SEQ ID NO: 27). Consensus sequence disclosed 
               
               
                 as SEQ ID NO: 142. 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Q 
                 I  
                 E 
                 Y 
                 L 
                 
                   A 
                 
                 K 
                 Q 
                 
                   I 
                 
                 
                   V 
                 
                 D 
                 N 
                 
                   A 
                 
                 
                   I 
                 
                 Q 
                 Q 
                 A 
               
               
                   
               
               
                 N 
                 L 
                 D 
                 F 
                 I 
                   
                 R 
                 N 
                   
                   
                 E 
                 Q 
                   
                   
                 N 
                 N 
                 L 
               
               
                   
                 V 
                   
                 T 
                 V 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 I 
               
               
                   
                   
                   
                 S 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 V 
               
               
                   
               
            
           
           
               
            
               
                 (SEQ ID NO: 56) 
               
               
                 NIEYLAKQIVDNAIQQA  
               
               
                   
               
               
                 (SEQ ID NO: 57) 
               
               
                 QLEYLAKQIVDNAIQQA  
               
               
                   
               
               
                 (SEQ ID NO: 58) 
               
               
                 QVEYLAKQIVDNAIQQA  
               
               
                   
               
               
                 (SEQ ID NO: 59) 
               
               
                 QIDYLAKQIVDNAIQQA  
               
               
                   
               
               
                 (SEQ ID NO: 60) 
               
               
                 QIEFLAKQIVDNAIQQA  
               
               
                   
               
               
                 (SEQ ID NO: 61) 
               
               
                 QIETLAKQIVDNAIQQA  
               
               
                   
               
               
                 (SEQ ID NO: 62) 
               
               
                 QIESLAKQIVDNAIQQA  
               
               
                   
               
               
                 (SEQ ID NO: 63) 
               
               
                 QIEYIAKQIVDNAIQQA  
               
               
                   
               
               
                 (SEQ ID NO: 64) 
               
               
                 QIEYVAKQIVDNAIQQA  
               
               
                   
               
               
                 (SEQ ID NO: 65) 
               
               
                 QIEYLARQIVDNAIQQA  
               
               
                   
               
               
                 (SEQ ID NO: 66) 
               
               
                 QIEYLAKNIVDNAIQQA  
               
               
                   
               
               
                 (SEQ ID NO: 67) 
               
               
                 QIEYLAKQIVENAIQQA  
               
               
                   
               
               
                 (SEQ ID NO: 68) 
               
               
                 QIEYLAKQIVDQAIQQA  
               
               
                   
               
               
                 (SEQ ID NO: 69) 
               
               
                 QIEYLAKQIVDNAINQA  
               
               
                   
               
               
                 (SEQ ID NO: 70) 
               
               
                 QIEYLAKQIVDNAIQNA  
               
               
                   
               
               
                 (SEQ ID NO: 71) 
               
               
                 QIEYLAKQIVDNAIQQL  
               
               
                   
               
               
                 (SEQ ID NO: 72) 
               
               
                 QIEYLAKQIVDNAIQQI  
               
               
                   
               
               
                 (SEQ ID NO: 73) 
               
               
                 QIEYLAKQIVDNAIQQV  
               
               
                   
               
            
           
         
       
     
     Gold et al. (2006, Mol Cell 24:383-95) utilized crystallography and peptide screening to develop a SuperAKAP-IS sequence (SEQ ID NO:74), exhibiting a five order of magnitude higher selectivity for the RII isoform of PKA compared with the RI isoform. Underlined residues indicate the positions of amino acid substitutions, relative to the AKAP-IS sequence, which increased binding to the DDD moiety of RIIα. In this sequence, the N-terminal Q residue is numbered as residue number 4 and the C-terminal A residue is residue number 20. Residues where substitutions could be made to affect the affinity for RIIα were residues 8, 11, 15, 16, 18, 19 and 20 (Gold et al., 2006). It is contemplated that in certain alternative embodiments, the SuperAKAP-IS sequence may be substituted for the AKAP-IS AD moiety sequence to prepare DNL constructs. Other alternative sequences that might be substituted for the AKAP-IS AD sequence are shown in SEQ ID NO:75-77. Substitutions relative to the AKAP-IS sequence are underlined. It is anticipated that, as with the AD2 sequence shown in SEQ ID NO:28, the AD moiety may also include the additional N-terminal residues cysteine and glycine and C-terminal residues glycine and cysteine. 
     
       
         
           
               
               
            
               
                   
                 SuperAKAP-IS 
               
               
                   
                 (SEQ ID NO: 74) 
               
               
                   
                 QIEY V AKQIVD Y AI H QA  
               
               
                   
                   
               
               
                   
                 Alternative AKAP sequences 
               
               
                   
                 (SEQ ID NO: 75) 
               
               
                   
                 QIEY K AKQIVD H AI H QA  
               
               
                   
                   
               
               
                   
                 (SEQ ID NO: 76) 
               
               
                   
                 QIEY H AKQIVD H AI H QA  
               
               
                   
                   
               
               
                   
                 (SEQ ID NO: 77) 
               
               
                   
                 QIEY V AKQIVD H AI H QA  
               
            
           
         
       
     
     FIG. 2 of Gold et al. disclosed additional DDD-binding sequences from a variety of AKAP proteins, shown below. 
     
       
         
           
               
               
            
               
                   
                 RII-Specific AKAPs 
               
               
                   
                 AKAP-KL 
               
               
                   
                 (SEQ ID NO: 78) 
               
               
                   
                 PLEYQAGLLVQNAIQQAI  
               
               
                   
                   
               
               
                   
                 AKAP79 
               
               
                   
                 (SEQ ID NO: 79) 
               
               
                   
                 LLIETASSLVKNAIQLSI  
               
               
                   
                   
               
               
                   
                 AKAP-Lbc 
               
               
                   
                 (SEQ ID NO: 80) 
               
               
                   
                 LIEEAASRIVDAVIEQVK  
               
               
                   
                   
               
               
                   
                 RI-Specific AKAPs 
               
               
                   
                 AKAPce 
               
               
                   
                 (SEQ ID NO: 81) 
               
               
                   
                 ALYQFADRFSELVISEAL  
               
               
                   
                   
               
               
                   
                 RIAD 
               
               
                   
                 (SEQ ID NO: 82) 
               
               
                   
                 LEQVANQLADQIIKEAT  
               
               
                   
                   
               
               
                   
                 PV38 
               
               
                   
                 (SEQ ID NO: 83) 
               
               
                   
                 FEELAWKIAKMIWSDVF  
               
               
                   
                   
               
               
                   
                 Dual-Specificity AKAPs 
               
               
                   
                 AKAP7 
               
               
                   
                 (SEQ ID NO: 84) 
               
               
                   
                 ELVRLSKRLVENAVLKAV  
               
               
                   
                   
               
               
                   
                 MAP2D 
               
               
                   
                 (SEQ ID NO: 85) 
               
               
                   
                 TAEEVSARIVQVVTAEAV  
               
               
                   
                   
               
               
                   
                 DAKAP1 
               
               
                   
                 (SEQ ID NO: 86) 
               
               
                   
                 QIKQAAFQLISQVILEAT  
               
               
                   
                   
               
               
                   
                 DAKAP2 
               
               
                   
                 (SEQ ID NO: 87) 
               
               
                   
                 LAWKIAKMIVSDVMQQ  
               
            
           
         
       
     
     Stokka et al. (2006, Biochem J 400:493-99) also developed peptide competitors of AKAP binding to PKA, shown in SEQ ID NO:88-09. The peptide antagonists were designated as Ht31 (SEQ ID NO:88), RIAD (SEQ ID NO:89) and PV-38 (SEQ ID NO:90). The Ht-31 peptide exhibited a greater affinity for the RH isoform of PKA, while the RIAD and PV-38 showed higher affinity for RI. 
     
       
         
           
               
               
            
               
                   
                 Ht31 
               
               
                   
                 (SEQ ID NO: 88) 
               
               
                   
                 DLIEEAASRIVDAVIEQVKAAGAY  
               
               
                   
                   
               
               
                   
                 RIAD 
               
               
                   
                 (SEQ ID NO: 89) 
               
               
                   
                 LEQYANQLADQIIKEATE  
               
               
                   
                   
               
               
                   
                 PV-38 
               
               
                   
                 (SEQ ID NO: 90) 
               
               
                   
                 FEELAWKIAKMIWSDVFQQC  
               
            
           
         
       
     
     Hundsrucker et al. (2006, Biochem J 396:297-306) developed still other peptide competitors for AKAP binding to PKA, with a binding constant as low as 0.4 nM to the DDD of the RII form of PKA. The sequences of various AKAP antagonistic peptides are provided in Table 1 of Hundsrucker et al., reproduced in Table 3 below. AKAPIS represents a synthetic RII subunit-binding peptide. All other peptides are derived from the RII-binding domains of the indicated AKAPs. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 AKAP Peptide sequences 
               
            
           
           
               
               
            
               
                   
                 Peptide Sequence 
               
               
                   
               
               
                 AKAPIS 
                 QIEYLAKQIVDNAIQQA  
               
               
                   
                 (SEQ ID NO: 27) 
               
               
                   
               
               
                 AKAPIS-P 
                 QIEYLAKQIPDNAIQQA  
               
               
                   
                 (SEQ ID NO: 91) 
               
               
                   
               
               
                 Ht31 
                 KGADLIEEAASRIVDAVIEQVKAAG  
               
               
                   
                 (SEQ ID NO: 92) 
               
               
                   
               
               
                 Ht31-P 
                 KGADLIEEAASRIPDAPIEQVKAAG  
               
               
                   
                 (SEQ ID NO: 93) 
               
               
                   
               
               
                 AKAP7δ-wt-pep 
                 PEDAELVRLSKRLVENAVLKAVQQY  
               
               
                   
                 (SEQ ID NO: 94) 
               
               
                   
               
               
                 AKAP7δ-L304T-pep 
                 PEDAELVRTSKRLVENAVLKAVQQY  
               
               
                   
                 (SEQ ID NO: 95) 
               
               
                   
               
               
                 AKAP7δ-L308D-pep 
                 PEDAELVRLSKRDVENAVLKAVQQY  
               
               
                   
                 (SEQ ID NO: 96) 
               
               
                   
               
               
                 AKAP7δ-P-pep 
                 PEDAELVRLSKRLPENAVLKAVQQY  
               
               
                   
                 (SEQ ID NO: 97) 
               
               
                   
               
               
                 AKAP7δ-PP-pep 
                 PEDAELVRLSKRLPENAPLKAVQQY  
               
               
                   
                 (SEQ ID NO: 98) 
               
               
                   
               
               
                 AKAP7δ-L314E-pep 
                 PEDAELVRLSKRLVENAVEKAVQQY  
               
               
                   
                 (SEQ ID NO: 99) 
               
               
                   
               
               
                 AKAP1-pep 
                 EEGLDRNEEIKRAAFQIISQVISEA  
               
               
                   
                 (SEQ ID NO: 100) 
               
               
                   
               
               
                 AKAP2-pep 
                 LVDDPLEYQAGLLVQNAIQQAIAEQ  
               
               
                   
                 (SEQ ID NO: 101) 
               
               
                   
               
               
                 AKAP5-pep 
                 QYETLLIETASSLVKNAIQLSIEQL  
               
               
                   
                 (SEQ ID NO: 102) 
               
               
                   
               
               
                 AKAP9-pep 
                 LEKQYQEQLEEEVAKVIVSMSIAFA  
               
               
                   
                 (SEQ ID NO: 103) 
               
               
                   
               
               
                 AKAP10-pep 
                 NTDEAQEELAWKIAKMIVSDIMQQA  
               
               
                   
                 (SEQ ID NO: 104) 
               
               
                   
               
               
                 AKAP11-pep 
                 VNLDKKAVLAEKIVAEAIEKAEREL  
               
               
                   
                 (SEQ ID NO: 105) 
               
               
                   
               
               
                 AKAP12-pep 
                 NGILELETKSSKLVQNIIQTAVDQF  
               
               
                   
                 (SEQ ID NO: 106) 
               
               
                   
               
               
                 AKAP14-pep 
                 TQDKNYEDELTQVALALVEDVINYA  
               
               
                   
                 (SEQ ID NO: 107) 
               
               
                   
               
               
                 Rab32-pep 
                 ETSAKDNINIEEAARFLVEKILVNH  
               
               
                   
                 (SEQ ID NO: 108) 
               
               
                   
               
            
           
         
       
     
     Residues that were highly conserved among the AD domains of different AKAP proteins are indicated below by underlining with reference to the AKAP IS sequence (SEQ ID NO:27). The residues are the same as observed by Alto et al. (2003), with the addition of the C-terminal alanine residue. (See FIG. 4 of Hundsrucker et al. (2006), incorporated herein by reference.) The sequences of peptide antagonists with particularly high affinities for the RII DDD sequence were those of AKAP-IS, AKAP7δ-wt-pep, AKAP7δ-L304T-pep and AKAP7δ-L308D-pep. 
     
       
         
           
               
               
            
               
                   
                 AKAP-IS 
               
               
                   
                 (SEQ ID NO: 27) 
               
               
                   
                 QIEYL A KQ IV DN AI QQ A   
               
            
           
         
       
     
     Can et al. (2001, J Biol Chem 276:17332-38) examined the degree of sequence homology between different AKAP-binding DDD sequences from human and non-human proteins and identified residues in the DDD sequences that appeared to be the most highly conserved among different DDD moieties. These are indicated below by underlining with reference to the human PKA RIIα DDD sequence of SEQ ID NO:25. Residues that were particularly conserved are further indicated by italics. The residues overlap with, but are not identical to those suggested by Kinderman et al. (2006) to be important for binding to AKAP proteins. The skilled artisan will realize that in designing sequence variants of DDD, it would be most preferred to avoid changing the most conserved residues (italicized), and it would be preferred to also avoid changing the conserved residues (underlined), while conservative amino acid substitutions may be considered for residues that are neither underlined nor italicized. 
     
       
         
           
               
               
            
               
                   
                 (SEQ ID NO: 25) 
               
               
                   
                 S HI Q   IP   P   GL   T E LL Q G Y T   V   EVLR   Q   QP   P   DL VE FA   VE   YF   TR   L   R E A   R   A  
               
            
           
         
       
     
     A modified set of conservative amino acid substitutions for the DDD1 (SEQ ID NO:25) sequence, based on the data of Carr et al. (2001) is shown in Table 4. Even with this reduced set of substituted sequences, there are over 65,000 possible alternative DDD moiety sequences that may be produced, tested and used by the skilled artisan without undue experimentation. The skilled artisan could readily derive such alternative DDD amino acid sequences as disclosed above for Table 1 and Table 2. 
     
       
         
           
               
             
               
                 TABLE 4 
               
               
                   
               
               
                 Conservative Amino Acid Substitutions in DDD1 (SEQ ID 
               
               
                 NO: 25). Consensus sequence disclosed as SEQ ID NO:143. 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
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     The skilled artisan will realize that these and other amino acid substitutions in the DDD or AD amino acid sequences may be utilized to produce alternative species within the genus of AD or DDD moieties, using techniques that are standard in the field and only routine experimentation. 
     Amino Acid Substitutions 
     In various embodiments, the disclosed methods and compositions may involve production and use of proteins or peptides with one or more substituted amino acid residues. For example, the DDD and/or AD sequences used to make DNL constructs may be modified as discussed above. 
     The skilled artisan will be aware that, in general, amino acid substitutions typically involve the replacement of an amino acid with another amino acid of relatively similar properties (i.e., conservative amino acid substitutions). The properties of the various amino acids and effect of amino acid substitution on protein structure and function have been the subject of extensive study and knowledge in the art. 
     For example, the hydropathic index of amino acids may be considered (Kyte &amp; Doolittle, 1982, J. Mol. Biol., 157:105-132). The relative hydropathic character of the amino acid contributes to the secondary structure of the resultant protein, which in turn defines the interaction of the protein with other molecules. Each amino acid has been assigned a hydropathic index on the basis of its hydrophobicity and charge characteristics (Kyte &amp; Doolittle, 1982), these are: isoleucine (+4.5); valine (+4.2); leucine (+3.8); phenylalanine (+2.8); cysteine/cystine (+2.5); methionine (+1.9); alanine (+1.8); glycine (−0.4); threonine (−0.7); serine (−0.8); tryptophan (−0.9); tyrosine (−1.3); proline (−1.6); histidine (−3.2); glutamate (−3.5); glutamine (−3.5); aspartate (−3.5); asparagine (−3.5); lysine (−3.9); and arginine (−4.5). In making conservative substitutions, the use of amino acids whose hydropathic indices are within ±2 is preferred, within ±1 are more preferred, and within ±0.5 are even more preferred. 
     Amino acid substitution may also take into account the hydrophilicity of the amino acid residue (e.g., U.S. Pat. No. 4,554,101). Hydrophilicity values have been assigned to amino acid residues: arginine (+3.0); lysine (+3.0); aspartate (+3.0); glutamate (+3.0); serine (+0.3); asparagine (+0.2); glutamine (+0.2); glycine (0); threonine (−0.4); proline (−0.5.+−0.1); alanine (−0.5); histidine (−0.5); cysteine (−1.0); methionine (−1.3); valine (−1.5); leucine (−1.8); isoleucine (−1.8); tyrosine (−2.3); phenylalanine (−2.5); tryptophan (−3.4). Replacement of amino acids with others of similar hydrophilicity is preferred. 
     Other considerations include the size of the amino acid side chain. For example, it would generally not be preferred to replace an amino acid with a compact side chain, such as glycine or serine, with an amino acid with a bulky side chain, e.g., tryptophan or tyrosine. The effect of various amino acid residues on protein secondary structure is also a consideration. Through empirical study, the effect of different amino acid residues on the tendency of protein domains to adopt an alpha-helical, beta-sheet or reverse turn secondary structure has been determined and is known in the art (see, e.g., Chou &amp; Fasman, 1974, Biochemistry, 13:222-245; 1978, Ann. Rev. Biochem., 47: 251-276; 1979, Biophys. J., 26:367-384). 
     Based on such considerations and extensive empirical study, tables of conservative amino acid substitutions have been constructed and are known in the art. For example: arginine and lysine; glutamate and aspartate; serine and threonine; glutamine and asparagine; and valine, leucine and isoleucine. Alternatively: Ala (A) leu, ile, val; Arg (R) gln, asn, lys; Asn (N) his, asp, lys, arg, gln; Asp (D) asn, glu; Cys (C) ala, ser; Gln (Q) glu, asn; Glu (E) gln, asp; Gly (G) ala; His (H) asn, gln, lys, arg; Ile (I) val, met, ala, phe, leu; Leu (L) val, met, ala, phe, ile; Lys (K) gln, asn, arg; Met (M) phe, ile, leu; Phe (F) leu, val, ile, ala, tyr; Pro (P) ala; Ser (S), thr; Thr (T) ser; Trp (W) phe, tyr; Tyr (Y) trp, phe, thr, ser; Val (V) ile, leu, met, phe, ala. 
     Other considerations for amino acid substitutions include whether or not the residue is located in the interior of a protein or is solvent exposed. For interior residues, conservative substitutions would include: Asp and Asn; Ser and Thr; Ser and Ala; Thr and Ala; Ala and Gly; Ile and Val; Val and Leu; Leu and Ile; Leu and Met; Phe and Tyr; Tyr and Trp. (See, e.g., PROWL website at rockefeller.edu) For solvent exposed residues, conservative substitutions would include: Asp and Asn; Asp and Glu; Glu and Gln; Glu and Ala; Gly and Asn; Ala and Pro; Ala and Gly; Ala and Ser; Ala and Lys; Ser and Thr; Lys and Arg; Val and Leu; Leu and Ile; Ile and Val; Phe and Tyr. (Id.) Various matrices have been constructed to assist in selection of amino acid substitutions, such as the PAM250 scoring matrix, Dayhoff matrix, Grantham matrix, McLachlan matrix, Doolittle matrix, Henikoff matrix, Miyata matrix, Fitch matrix, Jones matrix, Rao matrix, Levin matrix and Risler matrix (Idem.) 
     In determining amino acid substitutions, one may also consider the existence of intermolecular or intramolecular bonds, such as formation of ionic bonds (salt bridges) between positively charged residues (e.g., His, Arg, Lys) and negatively charged residues (e.g., Asp, Glu) or disulfide bonds between nearby cysteine residues. 
     Methods of substituting any amino acid for any other amino acid in an encoded protein sequence are well known and a matter of routine experimentation for the skilled artisan, for example by the technique of site-directed mutagenesis or by synthesis and assembly of oligonucleotides encoding an amino acid substitution and splicing into an expression vector construct. 
     Preparation of Antibodies 
     The complexes described herein may comprise one or more monoclonal antibodies or fragments thereof. Rodent monoclonal antibodies to specific antigens may be obtained by methods known to those skilled in the art. (See, e.g., Kohler and Milstein, Nature 256: 495 (1975), and Coligan et al. (eds.), CURRENT PROTOCOLS IN IMMUNOLOGY, VOL. 1, pages 2.5.1-2.6.7 (John Wiley &amp; Sons 1991)). 
     General techniques for cloning murine immunoglobulin variable domains have been disclosed, for example, by the publication of Orlandi et al., Proc. Nat&#39;l Acad. Sci. USA 86: 3833 (1989). Techniques for constructing chimeric antibodies are well known to those of skill in the art. As an example, Leung et al., Hybridoma 13:469 (1994), disclose how they produced an LL2 chimera by combining DNA sequences encoding the V k  and V H  domains of LL2 monoclonal antibody, an anti-CD22 antibody, with respective human and IgG 1  constant region domains. This publication also provides the nucleotide sequences of the LL2 light and heavy chain variable regions, V k  and V H , respectively. Techniques for producing humanized antibodies are disclosed, for example, by Jones et al., Nature 321: 522 (1986), Riechmann et al., Nature 332: 323 (1988), Verhoeyen et al., Science 239: 1534 (1988), Carter et al., Proc. Nat&#39;l Acad. Sci. USA 89: 4285 (1992), Sandhu, Crit. Rev. Biotech. 12: 437 (1992), and Singer et al., J. Immun. 150: 2844 (1993). 
     A chimeric antibody is a recombinant protein that contains the variable domains including the CDRs derived from one species of animal, such as a rodent antibody, while the remainder of the antibody molecule; i.e., the constant domains, is derived from a human antibody. Accordingly, a chimeric monoclonal antibody can also be humanized by replacing the sequences of the murine FR in the variable domains of the chimeric antibody with one or more different human FR. Specifically, mouse CDRs are transferred from heavy and light variable chains of the mouse immunoglobulin into the corresponding variable domains of a human antibody. As simply transferring mouse CDRs into human FRs often results in a reduction or even loss of antibody affinity, additional modification might be required in order to restore the original affinity of the murine antibody. This can be accomplished by the replacement of one or more some human residues in the FR regions with their murine counterparts to obtain an antibody that possesses good binding affinity to its epitope. (See, e.g., Tempest et al., Biotechnology 9:266 (1991) and Verhoeyen et al., Science 239: 1534 (1988)). 
     A fully human antibody can be obtained from a transgenic non-human animal. (See, e.g., Mendez et al., Nature Genetics, 15: 146-156, 1997; U.S. Pat. No. 5,633,425.) Methods for producing fully human antibodies using either combinatorial approaches or transgenic animals transformed with human immunoglobulin loci are known in the art (e.g., Mancini et al., 2004 , New Microbiol.  27:315-28; Conrad and Scheller, 2005 , Comb. Chem. High Throughput Screen.  8:117-26; Brekke and Loset, 2003 , Curr. Opin. Pharmacol.  3:544-50; each incorporated herein by reference). Such fully human antibodies are expected to exhibit even fewer side effects than chimeric or humanized antibodies and to function in vivo as essentially endogenous human antibodies. In certain embodiments, the claimed methods and procedures may utilize human antibodies produced by such techniques. 
     In one alternative, the phage display technique may be used to generate human antibodies (e.g., Dantas-Barbosa et al., 2005 , Genet. Mol. Res.  4:126-40, incorporated herein by reference). Human antibodies may be generated from normal humans or from humans that exhibit a particular disease state, such as a hematopoietic cancer (Dantas-Barbosa et al., 2005). The advantage to constructing human antibodies from a diseased individual is that the circulating antibody repertoire may be biased towards antibodies against disease-associated antigens. 
     In one non-limiting example of this methodology, Dantas-Barbosa et al. (2005) constructed a phage display library of human Fab antibody fragments from osteosarcoma patients. Generally, total RNA was obtained from circulating blood lymphocytes (Id.) Recombinant Fab were cloned from the μ, γ and κ chain antibody repertoires and inserted into a phage display library (Id.) RNAs were converted to cDNAs and used to make Fab cDNA libraries using specific primers against the heavy and light chain immunoglobulin sequences (Marks et al., 1991 , J. Mol. Biol.  222:581-97). Library construction was performed according to Andris-Widhopf et al. (2000, In:  Phage Display Laboratory Manual , Barbas et al. (eds), 1 st  edition, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. pp. 9.1 to 9.22, incorporated herein by reference). The final Fab fragments were digested with restriction endonucleases and inserted into the bacteriophage genome to make the phage display library. Such libraries may be screened by standard phage display methods. The skilled artisan will realize that this technique is exemplary only and any known method for making and screening human antibodies or antibody fragments by phage display may be utilized. 
     In another alternative, transgenic animals that have been genetically engineered to produce human antibodies may be used to generate antibodies against essentially any immunogenic target, using standard immunization protocols as discussed above. Methods for obtaining human antibodies from transgenic mice are described by Green et al., Nature Genet. 7:13 (1994), Lonberg et al., Nature 368:856 (1994), and Taylor et al., Int. Immun. 6:579 (1994). A non-limiting example of such a system is the XENOMOUSE® (e.g., Green et al., 1999 , J. Immunol. Methods  231:11-23, incorporated herein by reference) from Abgenix (Fremont, Calif.). In the XENOMOUSE® and similar animals, the mouse antibody genes have been inactivated and replaced by functional human antibody genes, while the remainder of the mouse immune system remains intact. 
     The XENOMOUSE® was transformed with germline-configured YACs (yeast artificial chromosomes) that contained portions of the human IgH and Ig kappa loci, including the majority of the variable region sequences, along accessory genes and regulatory sequences. The human variable region repertoire may be used to generate antibody producing B cells, which may be processed into hybridomas by known techniques. A XENOMOUSE® immunized with a target antigen will produce human antibodies by the normal immune response, which may be harvested and/or produced by standard techniques discussed above. A variety of strains of XENOMOUSE® are available, each of which is capable of producing a different class of antibody. Transgenically produced human antibodies have been shown to have therapeutic potential, while retaining the pharmacokinetic properties of normal human antibodies (Green et al., 1999). The skilled artisan will realize that the claimed compositions and methods are not limited to use of the XENOMOUSE® system but may utilize any transgenic animal that has been genetically engineered to produce human antibodies. 
     Antibody Cloning and Production 
     Various techniques, such as production of chimeric or humanized antibodies, may involve procedures of antibody cloning and construction. The antigen-binding Vκ (variable light chain) and V H  (variable heavy chain) sequences for an antibody of interest may be obtained by a variety of molecular cloning procedures, such as RT-PCR, 5′-RACE, and cDNA library screening. The V genes of an antibody from a cell that expresses a murine antibody can be cloned by PCR amplification and sequenced. To confirm their authenticity, the cloned V L  and V H  genes can be expressed in cell culture as a chimeric Ab as described by Orlandi et al., ( Proc. Natl. Acad. Sci ., USA, 86: 3833 (1989)). Based on the V gene sequences, a humanized antibody can then be designed and constructed as described by Leung et al. ( Mol. Immunol.,  32: 1413 (1995)). 
     cDNA can be prepared from any known hybridoma line or transfected cell line producing a murine antibody by general molecular cloning techniques (Sambrook et al., Molecular Cloning, A laboratory manual, 2 nd  Ed (1989)). The Vκ sequence for the antibody may be amplified using the primers VK1BACK and VK1FOR (Orlandi et al., 1989) or the extended primer set described by Leung et al. ( BioTechniques,  15: 286 (1993)). The V H  sequences can be amplified using the primer pair VH1BACK/VH1FOR (Orlandi et al., 1989) or the primers annealing to the constant region of murine IgG described by Leung et al. (Hybridoma, 13:469 (1994)). Humanized V genes can be constructed by a combination of long oligonucleotide template syntheses and PCR amplification as described by Leung et al. ( Mol. Immunol.,  32: 1413 (1995)). 
     PCR products for Vκ can be subcloned into a staging vector, such as a pBR327-based staging vector, VKpBR, that contains an Ig promoter, a signal peptide sequence and convenient restriction sites. PCR products for V H  can be subcloned into a similar staging vector, such as the pBluescript-based VHpBS. Expression cassettes containing the Vκ and V H  sequences together with the promoter and signal peptide sequences can be excised from VKpBR and VHpBS and ligated into appropriate expression vectors, such as pKh and pG1g, respectively (Leung et al., Hybridoma, 13:469 (1994)). The expression vectors can be co-transfected into an appropriate cell and supernatant fluids monitored for production of a chimeric, humanized or human antibody. Alternatively, the Vκ and V H  expression cassettes can be excised and subcloned into a single expression vector, such as pdHL2, as described by Gillies et al. ( J. Immunol. Methods  125:191 (1989) and also shown in Losman et al.,  Cancer,  80:2660 (1997)). 
     In an alternative embodiment, expression vectors may be transfected into host cells that have been pre-adapted for transfection, growth and expression in serum-free medium. Exemplary cell lines that may be used include the Sp/EEE, Sp/ESF and Sp/ESF-X cell lines (see, e.g., U.S. Pat. Nos. 7,531,327; 7,537,930 and 7,608,425; the Examples section of each of which is incorporated herein by reference). These exemplary cell lines are based on the Sp2/0 myeloma cell line, transfected with a mutant Bcl-EEE gene, exposed to methotrexate to amplify transfected gene sequences and pre-adapted to serum-free cell line for protein expression. 
     Antibody Allotypes 
     Immunogenicity of therapeutic antibodies is associated with increased risk of infusion reactions and decreased duration of therapeutic response (Baert et al., 2003, N Engl J Med 348:602-08). The extent to which therapeutic antibodies induce an immune response in the host may be determined in part by the allotype of the antibody (Stickler et al., 2011, Genes and Immunity 12:213-21). Antibody allotype is related to amino acid sequence variations at specific locations in the constant region sequences of the antibody. The allotypes of IgG antibodies containing a heavy chain γ-type constant region are designated as Gm allotypes (1976, J Immunol 117:1056-59). 
     For the common IgG1 human antibodies, the most prevalent allotype is G1m1 (Stickler et al., 2011, Genes and Immunity 12:213-21). However, the G1m3 allotype also occurs frequently in Caucasians (Id.). It has been reported that G1m1 antibodies contain allotypic sequences that tend to induce an immune response when administered to non-Glml (nG1 m1) recipients, such as G1m3 patients (Id.). Non-G1m1 allotype antibodies are not as immunogenic when administered to G1m1 patients (Id.). 
     The human G1m1 allotype comprises the amino acids D12 (Kabat position 356) and L14 (Kabat position 358) in the CH3 sequence of the heavy chain IgG1. The nG1m1 allotype comprises the amino acids E12 and M14 at the same locations. Both G1m1 and nG1m1 allotypes comprise an E13 residue in between the two variable sites and the allotypes are sometimes referred to as DEL and EEM allotypes. A non-limiting example of the heavy chain constant region sequence for an nGlml (G1m3) allotype antibody is shown in Example 1 below for the exemplary antibody veltuzumab (SEQ ID NO:144). 
     With regard to therapeutic antibodies, veltuzumab (G1m3) and rituximab (G1m17,1) are, respectively, humanized and chimeric IgG1 antibodies against CD20, of use for therapy of a wide variety of hematological malignancies and/or autoimmune diseases. Table 5 compares the allotype sequences of the heavy chain constant region sequences of rituximab vs. veltuzumab. The light chain constant region sequences of the two antibodies are identical. As shown in Table 5, rituximab (G1m17,1) is a DEL allotype IgG1, with an additional sequence variation at Kabat position 214 (heavy chain CH1) of lysine in rituximab vs. arginine in veltuzumab. It has been reported that veltuzumab is less immunogenic in subjects than rituximab (see, e.g., Morchhauser et al., 2009, J Clin Oncol 27:3346-53; Goldenberg et al., 2009, Blood 113:1062-70; Robak &amp; Robak, 2011, BioDrugs 25:13-25), an effect that has been attributed to the difference between humanized and chimeric antibodies. However, the difference in allotypes between the EEM and DEL allotypes likely also accounts for the lower immunogenicity of veltuzumab. 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 Allotypes of Rituximab vs. Veltuzumab 
               
            
           
           
               
               
               
            
               
                   
                   
                 Heavy chain position and  
               
               
                   
                   
                 associated allotypes 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Complete  
                 214  
                 356/358  
                 431  
               
               
                   
                 allotype 
                 (allotype) 
                 (allotype) 
                 (allotype) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 Rituximab 
                 G1m17,1 
                 K 
                 17 
                 D/L 
                 1 
                 A 
                 — 
               
               
                 Veltuzumab 
                 G1m3 
                 R 
                 3 
                 E/M 
                 — 
                 A 
                 — 
               
               
                   
               
            
           
         
       
     
     In order to reduce the immunogenicity of therapeutic antibodies in individuals of nG1m1 genotype, it is desirable to select the allotype of the antibody to correspond to the EEM allotype, with a glutamate residue at Kabat position 356, a methionine at Kabat position 358, and preferably an arginine residue at Kabat position 214. Surprisingly, it was found that repeated subcutaneous administration of G1m3 antibodies over a long period of time did not result in a significant immune response. 
     Known Antibodies 
     In various embodiments, the claimed methods and compositions may utilize any of a variety of antibodies known in the art. Antibodies of use may be commercially obtained from a number of known sources. For example, a variety of antibody secreting hybridoma lines are available from the American Type Culture Collection (ATCC, Manassas, Va.). A large number of antibodies against various disease targets have been deposited at the ATCC and/or have published variable region sequences and are available for use in the claimed methods and compositions. See, e.g., U.S. Pat. Nos. 7,312,318; 7,282,567; 7,151,164; 7,074,403; 7,060,802; 7,056,509; 7,049,060; 7,045,132; 7,041,803; 7,041,802; 7,041,293; 7,038,018; 7,037,498; 7,012,133; 7,001,598; 6,998,468; 6,994,976; 6,994,852; 6,989,241; 6,974,863; 6,965,018; 6,964,854; 6,962,981; 6,962,813; 6,956,107; 6,951,924; 6,949,244; 6,946,129; 6,943,020; 6,939,547; 6,921,645; 6,921,645; 6,921,533; 6,919,433; 6,919,078; 6,916,475; 6,905,681; 6,899,879; 6,893,625; 6,887,468; 6,887,466; 6,884,594; 6,881,405; 6,878,812; 6,875,580; 6,872,568; 6,867,006; 6,864,062; 6,861,511; 6,861,227; 6,861,226; 6,838,282; 6,835,549; 6,835,370; 6,824,780; 6,824,778; 6,812,206; 6,793,924; 6,783,758; 6,770,450; 6,767,711; 6,764,688; 6,764,681; 6,764,679; 6,743,898; 6,733,981; 6,730,307; 6,720,155; 6,716,966; 6,709,653; 6,693,176; 6,692,908; 6,689,607; 6,689,362; 6,689,355; 6,682,737; 6,682,736; 6,682,734; 6,673,344; 6,653,104; 6,652,852; 6,635,482; 6,630,144; 6,610,833; 6,610,294; 6,605,441; 6,605,279; 6,596,852; 6,592,868; 6,576,745; 6,572,856; 6,566,076; 6,562,618; 6,545,130; 6,544,749; 6,534,058; 6,528,625; 6,528,269; 6,521,227; 6,518,404; 6,511,665; 6,491,915; 6,488,930; 6,482,598; 6,482,408; 6,479,247; 6,468,531; 6,468,529; 6,465,173; 6,461,823; 6,458,356; 6,455,044; 6,455,040, 6,451,310; 6,444,206′ 6,441,143; 6,432,404; 6,432,402; 6,419,928; 6,413,726; 6,406,694; 6,403,770; 6,403,091; 6,395,276; 6,395,274; 6,387,350; 6,383,759; 6,383,484; 6,376,654; 6,372,215; 6,359,126; 6,355,481; 6,355,444; 6,355,245; 6,355,244; 6,346,246; 6,344,198; 6,340,571; 6,340,459; 6,331,175; 6,306,393; 6,254,868; 6,187,287; 6,183,744; 6,129,914; 6,120,767; 6,096,289; 6,077,499; 5,922,302; 5,874,540; 5,814,440; 5,798,229; 5,789,554; 5,776,456; 5,736,119; 5,716,595; 5,677,136; 5,587,459; 5,443,953, 5,525,338, the Examples section of each of which is incorporated herein by reference. These are exemplary only and a wide variety of other antibodies and their hybridomas are known in the art. The skilled artisan will realize that antibody sequences or antibody-secreting hybridomas against almost any disease-associated antigen may be obtained by a simple search of the ATCC, NCBI and/or USPTO databases for antibodies against a selected disease-associated target of interest. The antigen binding domains of the cloned antibodies may be amplified, excised, ligated into an expression vector, transfected into an adapted host cell and used for protein production, using standard techniques well known in the art. 
     Exemplary known antibodies that may be of use for therapy of cancer or autoimmune disease within the scope of the claimed methods and compositions include, but are not limited to, LL1 (anti-CD74), LL2 and RFB4 (anti-CD22), RS7 (anti-epithelial glycoprotein-1 (EGP-1)), PAM4 and KC4 (both anti-mucin), MN-14 (anti-carcinoembryonic antigen (CEA or CEACAM5, also known as CD66e)), Mu-9 (anti-colon-specific antigen-p), Immu-31 (an anti-alpha-fetoprotein), TAG-72 (e.g., CC49), Tn, J591 or HuJ591 (anti-PSMA (prostate-specific membrane antigen)), AB-PG1-XG1-026 (anti-PSMA dimer), D2/B (anti-PSMA), G250 (an anti-carbonic anhydrase IX MAb), hL243 (anti-HLA-DR), R1 (anti-IGF-1R), A20 (anti-CD20), A19 (anti-CD19), MN-3 or MN-15 (anti-CEACAM6), alemtuzumab (anti-CD52), bevacizumab (anti-VEGF), cetuximab (anti-EGFR), gemtuzumab (anti-CD33), ibritumomab tiuxetan (anti-CD20); panitumumab (anti-EGFR); rituximab (anti-CD20); tositumomab (anti-CD20); GA101 (anti-CD20); and trastuzumab (anti-ErbB2). Such antibodies are known in the art (e.g., U.S. Pat. Nos. 5,686,072; 5,874,540; 6,107,090; 6,183,744; 6,306,393; 6,653,104; 6,730,300; 6,899,864; 6,926,893; 6,962,702; 7,074,403; 7,230,084; 7,238,785; 7,238,786; 7,256,004; 7,282,567; 7,300,655; 7,312,318; 7,585,491; 7,612,180; 7,642,239; and U.S. Patent Application Publ. No. 20040202666 (now abandoned); 20050271671; and 20060193865; the Examples section of each incorporated herein by reference.) 
     Specific known antibodies of use include, but are not limited to, hPAM4 (U.S. Pat. No. 7,282,567), hA20 (U.S. Pat. No. 7,251,164), hAl9 (U.S. Pat. No. 7,109,304), hIMMU31 (U.S. Pat. No. 7,300,655), hLL1 (U.S. Pat. No. 7,312,318,), hLL2 (U.S. Pat. No. 7,074,403), hMu-9 (U.S. Pat. No. 7,387,773), hL243 (U.S. Pat. No. 7,612,180), hMN-14 (U.S. Pat. No. 6,676,924), hMN-15 (U.S. Pat. No. 7,541,440), hR1 (U.S. patent application Ser. No. 12/689,336), hRS7 (U.S. Pat. No. 7,238,785), hMN-3 (U.S. Pat. No. 7,541,440), 15B8 (anti-CD40, U.S. Pat. No. 7,820,170), AB-PG1-XG1-026 (U.S. patent application Ser. No. 11/983,372, deposited as ATCC PTA-4405 and PTA-4406) and D2/B (WO 2009/130575). Other known antibodies are disclosed, for example, in U.S. Pat. Nos. 5,686,072; 5,874,540; 6,107,090; 6,183,744; 6,306,393; 6,653,104; 6,730.300; 6,899,864; 6,926,893; 6,962,702; 7,074,403; 7,230,084; 7,238,785; 7,238,786; 7,256,004; 7,282,567; 7,300,655; 7,312,318; 7,585,491; 7,612,180; 7,642,239; and U.S. Patent Application Publ. No. 20040202666 (now abandoned); 20050271671; and 20060193865. The text of each recited patent or application is incorporated herein by reference with respect to the Figures and Examples sections. 
     Anti-TNF-α antibodies are known in the art and may be of use to treat immune diseases, such as autoimmune disease, immune dysfunction (e.g., graft-versus-host disease, organ transplant rejection) or diabetes. Known antibodies against TNF-α include the human antibody CDP571 (Ofei et al., 2011, Diabetes 45:881-85); murine antibodies MTNFAI, M2TNFAI, M3TNFAI, M3TNFABI, M302B and M303 (Thermo Scientific, Rockford, Ill.); infliximab (Centocor, Malvern, Pa.); certolizumab pegol (UCB, Brussels, Belgium); and adalimumab (Abbott, Abbott Park, Ill.). These and many other known anti-TNF-α antibodies may be used in the claimed methods and compositions. Other antibodies of use for therapy of immune dysregulatory or autoimmune disease include, but are not limited to, anti-B-cell antibodies such as veltuzumab, epratuzumab, milatuzumab or hL243; tocilizumab (anti-IL-6 receptor); basiliximab (anti-CD25); daclizumab (anti-CD25); efalizumab (anti-CD11a); GA101 (anti-CD20; Glycart Roche); muromonab-CD3 (anti-CD3 receptor); Benlysta (Human Genome Sciences); anti-CD40L (UCB, Brussels, Belgium); natalizumab (anti-α4 integrin) and omalizumab (anti-IgE). 
     Type-1 and Type-2 diabetes may be treated using known antibodies against B-cell antigens, such as CD22 (epratuzumab), CD74 (milatuzumab), CD19 (hA19), CD20 (veltuzumab) or HLA-DR (hL243) (see, e.g., Winer et al., 2011, Nature Med 17:610-18). Anti-CD3 antibodies also have been proposed for therapy of type 1 diabetes (Cernea et al., 2010, Diabetes Metab Rev 26:602-05). 
     Macrophage migration inhibitory factor (MIF) is an important regulator of innate and adaptive immunity and apoptosis. It has been reported that CD74 is the endogenous receptor for MIF (Leng et al., 2003, J Exp Med 197:1467-76). The therapeutic effect of antagonistic anti-CD74 antibodies on MIF-mediated intracellular pathways may be of use for treatment of a broad range of disease states, such as cancers of the bladder, prostate, breast, lung, colon and chronic lymphocytic leukemia (e.g., Meyer-Siegler et al., 2004, BMC Cancer 12:34; Shachar &amp; Haran, 2011, Leuk Lymphoma 52:1446-54); autoimmune diseases such as rheumatoid arthritis and systemic lupus erythematosus (Morand &amp; Leech, 2005, Front Biosci 10:12-22; Shachar &amp; Haran, 2011, Leuk Lymphoma 52:1446-54); kidney diseases such as renal allograft rejection (Lan, 2008, Nephron Exp Nephrol. 109:e79-83); and numerous inflammatory diseases (Meyer-Siegler et al., 2009, Mediators Inflamm epub Mar. 22, 2009; Takahashi et al., 2009, Respir Res 10:33; Milatuzumab (hLL1) is an exemplary anti-CD74 antibody of therapeutic use for treatment of MIF-mediated diseases. 
     Antibody Fragments 
     Antibody fragments which recognize specific epitopes can be generated by known techniques. The antibody fragments are antigen binding portions of an antibody, such as F(ab) 2 , Fab′, Fab, Fv, scFv and the like. Other antibody fragments include, but are not limited to, F(ab′) 2  fragments which can be produced by pepsin digestion of the antibody molecule and Fab′ fragments which can be generated by reducing disulfide bridges of the F(ab′) 2  fragments. Alternatively, Fab′ expression libraries can be constructed (Huse et al., 1989, Science, 246:1274-1281) to allow rapid and easy identification of monoclonal Fab′ fragments with the desired specificity. 
     A single chain Fv molecule (scFv) comprises a VL domain and a VH domain. The VL and VH domains associate to form a target binding site. These two domains are further covalently linked by a peptide linker (L). Methods for making scFv molecules and designing suitable peptide linkers are disclosed in U.S. Pat. No. 4,704,692, U.S. Pat. No. 4,946,778, R. Raag and M. Whitlow, “Single Chain Fvs.” FASEB Vol 9:73-80 (1995) and R. E. Bird and B. W. Walker, “Single Chain Antibody Variable Regions,” TIBTECH, Vol 9: 132-137 (1991). 
     An antibody fragment can be prepared by known methods, for example, as disclosed by Goldenberg, U.S. Pat. Nos. 4,036,945 and 4,331,647 and references contained therein. Also, see Nisonoff et al., Arch Biochem. Biophys. 89: 230 (1960); Porter, Biochem. J. 73: 119 (1959), Edelman et al., in METHODS IN ENZYMOLOGY VOL. 1, page 422 (Academic Press 1967), and Coligan at pages 2.8.1-2.8.10 and 2.10.-2.10.4. 
     A single complementarity-determining region (CDR) is a segment of the variable region of an antibody that is complementary in structure to the epitope to which the antibody binds and is more variable than the rest of the variable region. Accordingly, a CDR is sometimes referred to as hypervariable region. A variable region comprises three CDRs. CDR peptides can be obtained by constructing genes encoding the CDR of an antibody of interest. Such genes are prepared, for example, by using the polymerase chain reaction to synthesize the variable region from RNA of antibody-producing cells. (See, e.g., Larrick et al., Methods: A Companion to Methods in Enzymology 2: 106 (1991); Courtenay-Luck, “Genetic Manipulation of Monoclonal Antibodies,” in MONOCLONAL ANTIBODIES: PRODUCTION, ENGINEERING AND CLINICAL APPLICATION, Ritter et al. (eds.), pages 166-179 (Cambridge University Press 1995); and Ward et al., “Genetic Manipulation and Expression of Antibodies,” in MONOCLONAL ANTIBODIES: PRINCIPLES AND APPLICATIONS, Birch et al., (eds.), pages 137-185 (Wiley-Liss, Inc. 1995). 
     Another form of an antibody fragment is a single-domain antibody (dAb), sometimes referred to as a single chain antibody. Techniques for producing single-domain antibodies are well known in the art (see, e.g., Cossins et al., Protein Expression and Purification, 2007, 51:253-59; Shuntao et al., Molec Immunol 2006, 43:1912-19; Tanha et al., J. Biol. Chem. 2001, 276:24774-780). Single domain antibodies may be obtained, for example, from camels, alpacas or llamas by standard immunization techniques. (See, e.g., Muyldermans et al., TIBS 26:230-235, 2001; Yau et al., J Immunol Methods 281:161-75, 2003; Maass et al., J Immunol Methods 324:13-25, 2007). They can have potent antigen-binding capacity and can interact with novel epitopes that are inaccessible to conventional V H -V L  pairs. (Muyldermans et al., 2001). Alpaca serum IgG contains about 50% camelid heavy chain only IgG antibodies (HCAbs) (Maass et al., 2007). Alpacas may be immunized with known antigens, such as TNF-α, and single domain antibodies can be isolated that bind to and neutralize the target antigen (Maass et al., 2007). PCR primers that amplify virtually all alpaca antibody coding sequences have been identified and may be used to construct single domain phage display libraries, which can be used for antibody fragment isolation by standard biopanning techniques well known in the art (Maass et al., 2007). 
     In certain embodiments, the sequences of antibodies or antibody fragments, such as the Fc portions of antibodies, may be varied to optimize their physiological characteristics, such as the half-life in serum. Methods of substituting amino acid sequences in proteins are widely known in the art, such as by site-directed mutagenesis (e.g. Sambrook et al., Molecular Cloning, A laboratory manual, 2 nd  Ed, 1989). In preferred embodiments, the variation may involve the addition or removal of one or more glycosylation sites in the Fc sequence (e.g., U.S. Pat. No. 6,254,868, the Examples section of which is incorporated herein by reference). In other preferred embodiments, specific amino acid substitutions in the Fc sequence may be made (e.g., Hornick et al., 2000, J Nucl Med 41:355-62; Hinton et al., 2006, J Immunol 176:346-56; Petkova et al. 2006, Int Immunol 18:1759-69; U.S. Pat. No. 7,217,797). 
     Multispecific and Multivalent Antibodies 
     Various embodiments may concern use of multispecific and/or multivalent antibodies. For example, an anti-CD74 antibody or fragment thereof and an anti-CD20 antibody or fragment thereof may be joined together by means such as the dock-and-lock technique described above. Other combinations of antibodies or fragments thereof may be utilized. For example, the anti-CD74 antibody could be combined with another antibody against a different epitope of the same antigen, or alternatively with an antibody against another antigen, such as CD4, CD5, CD8, CD14, CD15, CD19, CD20, CD21, CD22, CD23, CD25, CD33, CD37, CD38, CD40, CD40L, CD46, CD52, CD54, CD74, CD80, CD126, CD138, B7, HM1.24, HLA-DR, an angiogenesis factor, tenascin, VEGF, PIGF, ED-B fibronectin, an oncogene, an oncogene product, NCA 66a-d, necrosis antigens, Ii (HLA-DR invariant chain), IL-2, T101, TAC, IL-6, MUC-1, TRAIL-R1 (DR4) or TRAIL-R2 (DR5). 
     Methods for producing bispecific antibodies include engineered recombinant antibodies which have additional cysteine residues so that they crosslink more strongly than the more common immunoglobulin isotypes. (See, e.g., FitzGerald et al, Protein Eng 10:1221-1225, 1997). Another approach is to engineer recombinant fusion proteins linking two or more different single-chain antibody or antibody fragment segments with the needed dual specificities. (See, e.g., Coloma et al., Nature Biotech. 15:159-163, 1997). A variety of bispecific antibodies can be produced using molecular engineering. In one form, the bispecific antibody may consist of, for example, a scFv with a single binding site for one antigen and a Fab fragment with a single binding site for a second antigen. In another form, the bispecific antibody may consist of, for example, an IgG with two binding sites for one antigen and two scFv with two binding sites for a second antigen. 
     Immunoconiugates 
     In certain embodiments, an antibody or antibody fragment may be directly attached to one or more therapeutic agents to form an immunoconjugate. Therapeutic agents may be attached, for example to reduced SH groups and/or to carbohydrate side chains. A therapeutic agent can be attached at the hinge region of a reduced antibody component via disulfide bond formation. Alternatively, such agents can be attached using a heterobifunctional cross-linker, such as N-succinyl 3-(2-pyridyldithio)propionate (SPDP). Yu et al., Int. J. Cancer 56: 244 (1994). General techniques for such conjugation are well-known in the art. See, for example, Wong, CHEMISTRY OF PROTEIN CONJUGATION AND CROSS-LINKING (CRC Press 1991); Upeslacis et al., “Modification of Antibodies by Chemical Methods,” in MONOCLONAL ANTIBODIES: PRINCIPLES AND APPLICATIONS, Birch et al. (eds.), pages 187-230 (Wiley-Liss, Inc. 1995); Price, “Production and Characterization of Synthetic Peptide-Derived Antibodies,” in MONOCLONAL ANTIBODIES: PRODUCTION, ENGINEERING AND CLINICAL APPLICATION, Ritter et al. (eds.), pages 60-84 (Cambridge University Press 1995). Alternatively, the therapeutic agent can be conjugated via a carbohydrate moiety in the Fc region of the antibody. 
     Methods for conjugating functional groups to antibodies via an antibody carbohydrate moiety are well-known to those of skill in the art. See, for example, Shih et al.,  Int. J. Cancer  41: 832 (1988); Shih et al.,  Int. J. Cancer  46: 1101 (1990); and Shih et al., U.S. Pat. No. 5,057,313, the Examples section of which is incorporated herein by reference. The general method involves reacting an antibody having an oxidized carbohydrate portion with a carrier polymer that has at least one free amine function. This reaction results in an initial Schiff base (imine) linkage, which can be stabilized by reduction to a secondary amine to form the final conjugate. 
     The Fc region may be absent if the antibody component of the immunoconjugate is an antibody fragment. However, it is possible to introduce a carbohydrate moiety into the light chain variable region of a full length antibody or antibody fragment. See, for example, Leung et al.,  J. Immunol.  154: 5919 (1995); U.S. Pat. Nos. 5,443,953 and 6,254,868, the Examples section of which is incorporated herein by reference. The engineered carbohydrate moiety is used to attach the therapeutic or diagnostic agent. 
     An alternative method for attaching therapeutic agents to an antibody or fragment involves use of click chemistry reactions. The click chemistry approach was originally conceived as a method to rapidly generate complex substances by joining small subunits together in a modular fashion. (See, e.g., Kolb et al., 2004, Angew Chem Int Ed 40:3004-31; Evans, 2007, Aust J Chem 60:384-95.) Various forms of click chemistry reaction are known in the art, such as the Huisgen 1,3-dipolar cycloaddition copper catalyzed reaction (Tornoe et al., 2002, J Organic Chem 67:3057-64), which is often referred to as the “click reaction.” Other alternatives include cycloaddition reactions such as the Diels-Alder, nucleophilic substitution reactions (especially to small strained rings like epoxy and aziridine compounds), carbonyl chemistry formation of urea compounds and reactions involving carbon-carbon double bonds, such as alkynes in thiol-yne reactions. 
     The azide alkyne Huisgen cycloaddition reaction uses a copper catalyst in the presence of a reducing agent to catalyze the reaction of a terminal alkyne group attached to a first molecule. In the presence of a second molecule comprising an azide moiety, the azide reacts with the activated alkyne to form a 1,4-disubstituted 1,2,3-triazole. The copper catalyzed reaction occurs at room temperature and is sufficiently specific that purification of the reaction product is often not required. (Rostovstev et al., 2002, Angew Chem Int Ed 41:2596; Tornoe et al., 2002, J Org Chem 67:3057.) The azide and alkyne functional groups are largely inert towards biomolecules in aqueous medium, allowing the reaction to occur in complex solutions. The triazole formed is chemically stable and is not subject to enzymatic cleavage, making the click chemistry product highly stable in biological systems. Although the copper catalyst is toxic to living cells, the copper-based click chemistry reaction may be used in vitro for immunoconjugate formation. 
     A copper-free click reaction has been proposed for covalent modification of biomolecules. (See, e.g., Agard et al., 2004, J Am Chem Soc 126:15046-47.) The copper-free reaction uses ring strain in place of the copper catalyst to promote a [3+2] azide-alkyne cycloaddition reaction (Id.) For example, cyclooctyne is an 8-carbon ring structure comprising an internal alkyne bond. The closed ring structure induces a substantial bond angle deformation of the acetylene, which is highly reactive with azide groups to form a triazole. Thus, cyclooctyne derivatives may be used for copper-free click reactions (Id.) 
     Another type of copper-free click reaction was reported by Ning et al. (2010, Angew Chem Int Ed 49:3065-68), involving strain-promoted alkyne-nitrone cycloaddition. To address the slow rate of the original cyclooctyne reaction, electron-withdrawing groups are attached adjacent to the triple bond (Id.) Examples of such substituted cyclooctynes include difluorinated cyclooctynes, 4-dibenzocyclooctynol and azacyclooctyne (Id.) An alternative copper-free reaction involved strain-promoted akyne-nitrone cycloaddition to give N-alkylated isoxazolines (Id.) The reaction was reported to have exceptionally fast reaction kinetics and was used in a one-pot three-step protocol for site-specific modification of peptides and proteins (Id.) Nitrones were prepared by the condensation of appropriate aldehydes with N-methylhydroxylamine and the cycloaddition reaction took place in a mixture of acetonitrile and water (Id.) These and other known click chemistry reactions may be used to attach therapeutic agents to antibodies in vitro. 
     The specificity of the click chemistry reaction may be used as a substitute for the antibody-hapten binding interaction used in pretargeting with bispecific antibodies. In this alternative embodiment, the specific reactivity of e.g., cyclooctyne moieties for azide moieties or alkyne moieties for nitrone moieties may be used in an in vivo cycloaddition reaction. An antibody, antibody fragment or antibody-based complex is activated by incorporation of a substituted cyclooctyne, an azide or a nitrone moiety. A targetable construct is labeled with one or more diagnostic or therapeutic agents and a complementary reactive moiety. I.e., where the antibody comprises a cyclooctyne, the targetable construct will comprise an azide; where the antibody comprises a nitrone, the targetable construct will comprise an alkyne, etc. The activated antibody or fragment is administered to a subject and allowed to localize to a targeted cell, tissue or pathogen, as disclosed for pretargeting protocols. The reactive labeled targetable construct is then administered. Because the cyclooctyne, nitrone or azide on the targetable construct is unreactive with endogenous biomolecules and highly reactive with the complementary moiety on the antibody, the specificity of the binding interaction results in the highly specific binding of the targetable construct to the tissue-localized antibody. 
     Therapeutic Agents 
     A wide variety of therapeutic reagents can be administered concurrently or sequentially with the subject anti-CD74 antibodies or antibody combinations. For example, drugs, toxins, oligonucleotides, immunomodulators, cytokine or chemokine inhibitors, proapoptotic agents, tyrosine kinase inhibitors, sphingosine inhibitors, hormones, hormone antagonists, enzymes, enzyme inhibitors, radionuclides, angiogenesis inhibitors, other antibodies or fragments thereof, etc. The therapeutic agents recited here are those agents that also are useful for administration separately with an antibody or fragment thereof as described above. Therapeutic agents include, for example, cytotoxic agents such as vinca alkaloids, anthracyclines, gemcitabine, epipodophyllotoxins, taxanes, antimetabolites, alkylating agents, antibiotics, SN-38, COX-2 inhibitors, antimitotics, anti-angiogenic and pro-apoptotic agents, particularly doxorubicin, methotrexate, taxol, CPT-11, camptothecans, proteosome inhibitors, mTOR inhibitors, HDAC inhibitors, tyrosine kinase inhibitors, and others. 
     Other useful cytotoxic agents include nitrogen mustards, alkyl sulfonates, nitrosoureas, triazenes, folic acid analogs, COX-2 inhibitors, antimetabolites, pyrimidine analogs, purine analogs, platinum coordination complexes, mTOR inhibitors, tyrosine kinase inhibitors, proteosome inhibitors, HDAC inhibitors, camptothecins, hormones, and the like. Suitable cytotoxic agents are described in REMINGTON&#39;S PHARMACEUTICAL SCIENCES, 19th Ed. (Mack Publishing Co. 1995), and in GOODMAN AND GILMAN&#39;S THE PHARMACOLOGICAL BASIS OF THERAPEUTICS, 7th Ed. (MacMillan Publishing Co. 1985), as well as revised editions of these publications. 
     In a preferred embodiment, conjugates of camptothecins and related compounds, such as SN-38, may be conjugated to an antibody, for example as disclosed in U.S. Pat. No. 7,591,994, the Examples section of which is incorporated herein by reference. 
     The therapeutic agent may be selected from the group consisting of aplidin, azaribine, anastrozole, azacytidine, bleomycin, bortezomib, bryostatin-1, busulfan, calicheamycin, camptothecin, 10-hydroxycamptothecin, carmustine, celebrex, chlorambucil, cisplatin, irinotecan (CPT-11), SN-38, carboplatin, cladribine, cyclophosphamide, cytarabine, dacarbazine, docetaxel, dactinomycin, daunomycin glucuronide, daunorubicin, dexamethasone, diethylstilbestrol, doxorubicin, doxorubicin glucuronide, epirubicin glucuronide, ethinyl estradiol, estramustine, etoposide, etoposide glucuronide, etoposide phosphate, floxuridine (FUdR), 3′,5′-O-dioleoyl-FudR (FUdR-dO), fludarabine, flutamide, fluorouracil, fluoxymesterone, gemcitabine, hydroxyprogesterone caproate, hydroxyurea, idarubicin, ifosfamide, L-asparaginase, leucovorin, lomustine, mechlorethamine, medroprogesterone acetate, egestrol acetate, melphalan, mercaptopurine, 6-mercaptopurine, methotrexate, mitoxantrone, mithramycin, mitomycin, mitotane, phenyl butyrate, prednisone, procarbazine, paclitaxel, pentostatin, PSI-341, semustine streptozocin, tamoxifen, taxanes, taxol, testosterone propionate, thalidomide, thioguanine, thiotepa, teniposide, topotecan, uracil mustard, velcade, vinblastine, vinorelbine, vincristine, ricin, abrin, ribonuclease, onconase, rapLRl, DNase I, Staphylococcal enterotoxin-A, pokeweed antiviral protein, gelonin, diphtheria toxin,  Pseudomonas  exotoxin, and  Pseudomonas  endotoxin. 
     A toxin can be of animal, plant or microbial origin. A toxin, such as  Pseudomonas  exotoxin, may also be complexed to or form the therapeutic agent portion of an immunoconjugate. Other toxins include ricin, abrin, ribonuclease (RNase), DNase I, Staphylococcal enterotoxin-A, pokeweed antiviral protein, onconase, gelonin, diphtheria toxin,  Pseudomonas  exotoxin, and  Pseudomonas  endotoxin. See, for example, Pastan et al., Cell 47:641 (1986), Goldenberg, C A—A Cancer Journal for Clinicians 44:43 (1994), Sharkey and Goldenberg, C A—A Cancer Journal for Clinicians 56:226 (2006). Additional toxins suitable for use are known to those of skill in the art and are disclosed in U.S. Pat. No. 6,077,499, the Examples section of which is incorporated herein by reference. 
     The therapeutic agent may be an enzyme selected from the group consisting of malate dehydrogenase, staphylococcal nuclease, delta-V-steroid isomerase, yeast alcohol dehydrogenase, alpha-glycerophosphate dehydrogenase, triose phosphate isomerase, horseradish peroxidase, alkaline phosphatase, asparaginase, glucose oxidase, beta-galactosidase, ribonuclease, urease, catalase, glucose-6-phosphate dehydrogenase, glucoamylase and acetylcholinesterase. 
     As used herein, the term “immunomodulator” includes cytokines, lymphokines, monokines, stem cell growth factors, lymphotoxins, hematopoietic factors, colony stimulating factors (CSF), interferons (IFN), parathyroid hormone, thyroxine, insulin, proinsulin, relaxin, prorelaxin, follicle stimulating hormone (FSH), thyroid stimulating hormone (TSH), luteinizing hormone (LH), hepatic growth factor, prostaglandin, fibroblast growth factor, prolactin, placental lactogen, OB protein, transforming growth factor (TGF), TGF-α, TGF-β, insulin-like growth factor (IGF), erythropoietin, thrombopoietin, tumor necrosis factor (TNF), TNF-α, TNF-β, mullerian-inhibiting substance, mouse gonadotropin-associated peptide, inhibin, activin, vascular endothelial growth factor, integrin, interleukin (IL), granulocyte-colony stimulating factor (G-CSF), granulocyte macrophage-colony stimulating factor (GM-CSF), interferon-α, interferon-β, interferon-γ, S1 factor, IL-1, IL-lcc, IL-2, IL-3, IL-4, IL-5, IL-6, IL-7, IL-8, IL-9, IL-10, IL-11, IL-12, IL-13, IL-14, IL-15, IL-16, IL-17, IL-18 IL-21, IL-23, IL-25, LIF, kit-ligand, FLT-3, angiostatin, thrombospondin, endostatin, and the like. 
     Exemplary anti-angiogenic agents may include angiostatin, endostatin, vasculostatin, canstatin, maspin, anti-VEGF binding molecules, anti-placental growth factor binding molecules, or anti-vascular growth factor binding molecules. 
     In certain embodiments, the antibody or complex may comprise one or more chelating moieties, such as NOTA, DOTA, DTPA, TETA, Tscg-Cys, or Tsca-Cys. In certain embodiments, the chelating moiety may form a complex with a therapeutic or diagnostic cation, such as Group II, Group III, Group IV, Group V, transition, lanthanide or actinide metal cations, Tc, Re, Bi, Cu, As, Ag, Au, At, or Pb. 
     The antibody or fragment thereof may be administered as an immunoconjugate comprising one or more radioactive isotopes useful for treating diseased tissue. Particularly useful therapeutic radionuclides include, but are not limited to  111 In,  177 Lu,  212 Bi,  213 Bi,  211 At,  62 Cb,  64 Cb,  67 Cb,  90 Y,  125 I,  131 I,  32 P,  33 P,  47 Sc,  111 Ag,  67 Ga,  142 Pr  153 Sm,  161 Tb,  166 Dy,  166 Ho,  186 Re,  188 Re,  189 Re,  212 Pb,  223 Ra,  225 Ac,  59 Fe,  75 Se,  77 As,  89 Sr,  99 Mo,  105 Rh,  109 Pd,  143 Pr,  149 Pm,  169 Er,  194 Ir,  198 Au,  199 Au and  211 Pb. The therapeutic radionuclide preferably has a decay energy in the range of 20 to 6,000 keV, preferably in the ranges 60 to 200 keV for an Auger emitter, 100-2,500 keV for a beta emitter and 4,000-6,000 keV for an alpha emitter. Maximum decay energies of useful beta-particle-emitting nuclides are preferably 20-5,000 keV, more preferably 100-4,000 keV and most preferably 500-2,500 keV. Also preferred are radionuclides that substantially decay with Auger-emitting particles. For example, Co-58, Ga-67, Br-80m, Tc-99m, Rh-103m, Pt-109, In-111, Sb-119, I-125, Ho-161, Os-189m and Ir-192. Decay energies of useful beta-particle-emitting nuclides are preferably &lt;1,000 keV, more preferably &lt;100 keV, and most preferably &lt;70 keV. Also preferred are radionuclides that substantially decay with generation of alpha-particles. Such radionuclides include, but are not limited to: Dy-152, At-211, Bi-212, Ra-223, Rn-219, Po-215, Bi-211, Ac-225, Fr-221, At-217, Bi-213 and Fm-255. Decay energies of useful alpha-particle-emitting radionuclides are preferably 2,000-10,000 keV, more preferably 3,000-8,000 keV, and most preferably 4,000-7,000 keV. 
     Additional potential therapeutic radioisotopes include  11 C,  13 N,  15 O,  75 Br,  198 Au,  224 Ac,  126 I,  113 I,  77 Br,  113m In,  95 Ru,  97 Ru,  103 Ru,  105 Ru,  107 Hg,  203 Hg,  121m Te,  122m Te,  125m Te,  165 Tm,  167 Tm,  168 Tm,  197 Pt,  109 Pd,  105 Rh,  142 Pr,  143 Pr,  161 Tb,  166 Ho,  199 Au,  57 Co,  51 Cr,  59 Fe,  75 Se,  201 Tl,  225 Ac,  76 Br,  169 Yb, and the like. 
     Interference RNA 
     In certain preferred embodiments the therapeutic agent may be a siRNA or interference RNA species. The siRNA, interference RNA or therapeutic gene may be attached to a carrier moiety that is conjugated to an antibody or fragment thereof. A variety of carrier moieties for siRNA have been reported and any such known carrier may be incorporated into a therapeutic antibody for use. Non-limiting examples of carriers include protamine (Rossi, 2005, Nat Biotech 23:682-84; Song et al., 2005, Nat Biotech 23:709-17); dendrimers such as PAMAM dendrimers (Pan et al., 2007, Cancer Res. 67:8156-8163); polyethylenimine (Schiffelers et al., 2004, Nucl Acids Res 32:e149); polypropyleneimine (Taratula et al., 2009, J Control Release 140:284-93); polylysine (Inoue et al., 2008, J Control Release 126:59-66); histidine-containing reducible polycations (Stevenson et al., 2008, J Control Release 130:46-56); histone H1 protein (Haberland et al., 2009, Mol Biol Rep 26:1083-93); cationic comb-type copolymers (Sato et al., 2007, J Control Release 122:209-16); polymeric micelles (U.S. Patent Application Publ. No. 20100121043); and chitosan-thiamine pyrophosphate (Rojanarata et al., 2008, Pharm Res 25:2807-14). The skilled artisan will realize that in general, polycationic proteins or polymers are of use as siRNA carriers. The skilled artisan will further realize that siRNA carriers can also be used to carry other oligonucleotide or nucleic acid species, such as anti-sense oligonucleotides or short DNA genes. 
     Known siRNA species of potential use include those specific for IKK-gamma (U.S. Pat. No. 7,022,828); VEGF, Flt-1 and Flk-1/KDR (U.S. Pat. No. 7,148,342); Bcl2 and EGFR (U.S. Pat. No. 7,541,453); CDC20 (U.S. Pat. No. 7,550,572); transducin (beta)-like 3 (U.S. Pat. No. 7,576,196); K-ras (U.S. Pat. No. 7,576,197); carbonic anhydrase II (U.S. Pat. No. 7,579,457); complement component 3 (U.S. Pat. No. 7,582,746); interleukin-1 receptor-associated kinase 4 (IRAK4) (U.S. Pat. No. 7,592,443); survivin (U.S. Pat. No. 7,608,7070); superoxide dismutase 1 (U.S. Pat. No. 7,632,938); MET proto-oncogene (U.S. Pat. No. 7,632,939); amyloid beta precursor protein (APP) (U.S. Pat. No. 7,635,771); IGF-1R (U.S. Pat. No. 7,638,621); ICAM1 (U.S. Pat. No. 7,642,349); complement factor B (U.S. Pat. No. 7,696,344); p53 (U.S. Pat. No. 7,781,575), and apolipoprotein B (U.S. Pat. No. 7,795,421), the Examples section of each referenced patent incorporated herein by reference. 
     Additional siRNA species are available from known commercial sources, such as Sigma-Aldrich (St Louis, Mo.), Invitrogen (Carlsbad, Calif.), Santa Cruz Biotechnology (Santa Cruz, Calif.), Ambion (Austin, Tex.), Dharmacon (Thermo Scientific, Lafayette, Colo.), Promega (Madison, Wis.), Minis Bio (Madison, Wis.) and Qiagen (Valencia, Calif.), among many others. Other publicly available sources of siRNA species include the siRNAdb database at the Stockholm Bioinformatics Centre, the MIT/ICBP siRNA Database, the RNAi Consortium shRNA Library at the Broad Institute, and the Probe database at NCBI. For example, there are 30,852 siRNA species in the NCBI Probe database. The skilled artisan will realize that for any gene of interest, either a siRNA species has already been designed, or one may readily be designed using publicly available software tools. Any such siRNA species may be delivered using the subject antibodies, antibody fragments or antibody complexes. 
     Exemplary siRNA species known in the art are listed in Table 6. Although siRNA is delivered as a double-stranded molecule, for simplicity only the sense strand sequences are shown in Table 6. 
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 Exemplary siRNA Sequences 
               
            
           
           
               
               
               
            
               
                 Target 
                 Sequence 
                 SEQ ID NO 
               
               
                   
               
               
                 VEGF R2 
                 AATGCGGCGGTGGTGACAGTA 
                 SEQ ID NO: 109 
               
               
                   
               
               
                 VEGF R2 
                 AAGCTCAGCACACAGAAAGAC 
                 SEQ ID NO: 110 
               
               
                   
               
               
                 CXCR4 
                 UAAAAUCUUCCUGCCCACCdTdT 
                 SEQ ID NO: 111 
               
               
                   
               
               
                 CXCR4 
                 GGAAGCUGUUGGCUGAAAAdTdT 
                 SEQ ID NO: 112 
               
               
                   
               
               
                 PPARC1 
                 AAGACCAGCCUCUUUGCCCAG 
                 SEQ ID NO: 113 
               
               
                   
               
               
                 Dynamin 2 
                 GGACCAGGCAGAAAACGAG 
                 SEQ ID NO: 114 
               
               
                   
               
               
                 Catenin 
                 CUAUCAGGAUGACGCGG 
                 SEQ ID NO: 115 
               
               
                   
               
               
                 E1A binding 
                 UGACACAGGCAGGCUUGACUU 
                 SEQ ID NO: 116 
               
               
                 protein 
                   
                   
               
               
                   
               
               
                 Plasminogen 
                 GGTGAAGAAGGGCGTCCAA 
                 SEQ ID NO: 117 
               
               
                 activator 
                   
                   
               
               
                   
               
               
                 K-ras 
                 GATCCGTTGGAGCTGTTGGCGTAGTT 
                 SEQ ID NO: 118 
               
               
                   
                 CAAGAGACTCGCCAACAGCTCCAACT 
                   
               
               
                   
                 TTTGGAAA 
                   
               
               
                   
               
               
                 Sortilin 1 
                 AGGTGGTGTTAACAGCAGAG 
                 SEQ ID NO: 119 
               
               
                   
               
               
                 Apolipoprotein E 
                 AAGGTGGAGCAAGCGGTGGAG 
                 SEQ ID NO: 120 
               
               
                   
               
               
                 Apolipoprotein E 
                 AAGGAGTTGAAGGCCGACAAA 
                 SEQ ID NO: 121 
               
               
                   
               
               
                 Bcl-X 
                 UAUGGAGCUGCAGAGGAUGdTdT 
                 SEQ ID NO: 122 
               
               
                   
               
               
                 Raf-1 
                 TTTGAATATCTGTGCTGAGAACACA 
                 SEQ ID NO: 123 
               
               
                   
                 GTTCTCAGCACAGATATTCTTTTT 
                   
               
               
                   
               
               
                 Heat shock 
                 AATGAGAAAAGCAAAAGGTGCCCTGTCTC 
                 SEQ ID NO: 124 
               
               
                 transcription  
                   
                   
               
               
                 factor 2 
                   
                   
               
               
                   
               
               
                 IGFBP3 
                 AAUCAUCAUCAAGAAAGGGCA 
                 SEQ ID NO: 125 
               
               
                   
               
               
                 Thioredoxin 
                 AUGACUGUCAGGAUGUUGCdTdT 
                 SEQ ID NO: 126 
               
               
                   
               
               
                 CD44 
                 GAACGAAUCCUGAAGACAUCU 
                 SEQ ID NO: 127 
               
               
                   
               
               
                 MMP14 
                 AAGCCTGGCTACAGCAATATGCCTGTCTC 
                 SEQ ID NO: 128 
               
               
                   
               
               
                 MAPKAPK2 
                 UGACCAUCACCGAGUUUAUdTdT 
                 SEQ ID NO: 129 
               
               
                   
               
               
                 FGFR1 
                 AAGTCGGACGCAACAGAGAAA 
                 SEQ ID NO: 130 
               
               
                   
               
               
                 ERBB2 
                 CUACCUUUCUACGGACGUGdTdT 
                 SEQ ID NO: 131 
               
               
                   
               
               
                 BCL2L1 
                 CTGCCTAAGGCGGATTTGAAT 
                 SEQ ID NO: 132 
               
               
                   
               
               
                 ABL1 
                 TTAUUCCUUCUUCGGGAAGUC 
                 SEQ ID NO: 133 
               
               
                   
               
               
                 CEACAM1 
                 AACCTTCTGGAACCCGCCCAC 
                 SEQ ID NO: 134 
               
               
                   
               
               
                 CD9 
                 GAGCATCTTCGAGCAAGAA 
                 SEQ ID NO: 135 
               
               
                   
               
               
                 CD151 
                 CATGTGGCACCGTTTGCCT 
                 SEQ ID NO: 136 
               
               
                   
               
               
                 Caspase 8 
                 AACTACCAGAAAGGTATACCT 
                 SEQ ID NO: 137 
               
               
                   
               
               
                 BRCA1 
                 UCACAGUGUCCUUUAUGUAdTdT 
                 SEQ ID NO: 138 
               
               
                   
               
               
                 p53 
                 GCAUGAACCGGAGGCCCAUTT 
                 SEQ ID NO: 139 
               
               
                   
               
               
                 CEACAM6 
                 CCGGACAGTTCCATGTATA 
                 SEQ ID NO: 140 
               
               
                   
               
            
           
         
       
     
     The skilled artisan will realize that Table 6 represents a very small sampling of the total number of siRNA species known in the art, and that any such known siRNA may be utilized in the claimed methods and compositions. 
     Immunotoxins Comprising Ranpirnase (Rap) 
     Ribonucleases, in particular, Rap (Lee, Exp Opin Biol Ther 2008; 8:813-27) and its more basic variant, amphinase (Ardelt et al., Curr Pharm Biotechnol 2008:9:215-25), are potential anti-tumor agents (Lee and Raines, Biodrugs 2008; 22:53-8). Rap is a single-chain ribonuclease of 104 amino acids originally isolated from the oocytes of  Rana pipiens . Rap exhibits cytostatic and cytotoxic effects on a variety of tumor cell lines in vitro, as well as antitumor activity in vivo. The amphibian ribonuclease enters cells via receptor-mediated endocytosis and once internalized into the cytosol, selectively degrades tRNA, resulting in inhibition of protein synthesis and induction of apoptosis. 
     Rap has completed a randomized Phase IIIb clinical trial, which compared the effectiveness of Rap plus doxorubicin with that of doxorubicin alone in patients with unresectable malignant mesothelioma, with the interim analysis showing that the MST for the combination was 12 months, while that of the monotherapy was 10 months (Mutti and Gaudino, Oncol Rev 2008; 2:61-5). Rap can be administered repeatedly to patients without an untoward immune response, with reversible renal toxicity reported to be dose-limiting (Mikulski et al., J Clin Oncol 2002; 20:274-81; Int J Oncol 1993; 3:57-64). 
     Conjugation or fusion of Rap to a tumor-targeting antibody or antibody fragment is a promising approach to enhance its potency, as first demonstrated for LL2-onconase (Newton et al., Blood 2001; 97:528-35), a chemical conjugate comprising Rap and a murine anti-CD22 monoclonal antibody (MAb), and subsequently for 2L-Rap-hLL1-γ4P, a fusion protein comprising Rap and a humanized anti-CD74 MAb (Stein et al., Blood 2004; 104:3705-11). 
     The method used to generate 2L-Rap-hLL1-γ4P allowed us to develop a series of structurally similar immunotoxins, referred to in general as 2L-Rap-X, all of which consist of two Rap molecules, each connected via a flexible linker to the N-terminus of one L chain of an antibody of interest (X). We have also generated another series of immunotoxins of the same design, referred to as 2LRap(Q)-X, by substituting Rap with its non-glycosylation form of Rap, designated as Rap(Q) to denote that the potential glycosylation site at Asn69 is changed to Gln (or Q, single letter code). For both series, we made the IgG as either IgG1 (γ1) or IgG4(γ4), and to prevent the formation of IgG4 half molecules (Aalberse and Schuurman, Immunology 2002; 105:9-19), we converted the serine residue in the hinge region (S228) of IgG4 to proline (γ4P). A pyroglutamate residue at the N-terminus of Rap is required for the RNase to be fully functional (Liao et al., Nucleic Acids Res 2003; 31:5247-55). 
     The skilled artisan will recognize that the cytotoxic RNase moieties suitable for use in the present invention include polypeptides having a native ranpirnase structure and all enzymatically active variants thereof. These molecules advantageously have an N-terminal pyroglutamic acid resides that appears essential for RNase activity and are not substantially inhibited by mammalian RNase inhibitors. Nucleic acid that encodes a native cytotoxic RNase may be prepared by cloning and restriction of appropriate sequences, or using DNA amplification with polymerase chain reaction (PCR). The amino acid sequence of  Rana pipiens  ranpirnase can be obtained from Ardelt et al., J. Biol. Chem., 256: 245 (1991), and cDNA sequences encoding native ranpirnase, or a conservatively modified variation thereof, can be gene-synthesized by methods similar to the en bloc V-gene assembly method used in hLL2 humanization. (Leung et al., Mol. Immunol., 32: 1413, 1995). Methods of making cytotoxic RNase variants are known in the art and are within the skill of the routineer. 
     As described in the Examples below, Rap conjugates of targeting antibodies may be made using the DNL technology. The DNL Rap-antibody constructs show potent cytotoxic activity that can be targeted to disease-associated cells. 
     Diagnostic Agents 
     In various embodiments, the antibodies, antibody fragments or antibody complexes may be conjugated to, or may bind a targetable construct comprising one or more diagnostic agents. Diagnostic agents are preferably selected from the group consisting of a radionuclide, a radiological contrast agent, a paramagnetic ion, a metal, a fluorescent label, a chemiluminescent label, an ultrasound contrast agent and a photoactive agent. Such diagnostic agents are well known and any such known diagnostic agent may be used. Non-limiting examples of diagnostic agents may include a radionuclide such as  18 F,  52 Fe,  110 In,  111 In,  177 Lu,  18 F,  52 Fe,  62 Cu,  64 Cu,  67 Cu,  67 Ga,  68 Ga,  86 Y,  90 Y,  89 Zr,  94m Tc,  94 Tc,  99m Tc,  120 I,  123 I,  124 I,  125 I,  131 I,  154-158 Gd,  32 P,  11 C,  13 N,  15 O,  186 Re,  188 Re,  51 Mn,  52m Mn,  55 Co,  72 As,  75 Br,  76 Br,  82m Rb,  83 Sr, or other gamma-, beta-, or positron-emitters. 
     Paramagnetic ions of use may include chromium (III), manganese (II), iron (III), iron (II), cobalt (II), nickel (II), copper (II), neodymium (III), samarium (III), ytterbium (III), gadolinium (III), vanadium (II), terbium (III), dysprosium (III), holmium (III) or erbium (III). Metal contrast agents may include lanthanum (III), gold (III), lead (II) or bismuth (III). 
     Ultrasound contrast agents may comprise liposomes, such as gas filled liposomes. Radiopaque diagnostic agents may be selected from compounds, barium compounds, gallium compounds, and thallium compounds. A wide variety of fluorescent labels are known in the art, including but not limited to fluorescein isothiocyanate, rhodamine, phycoerytherin, phycocyanin, allophycocyanin, o-phthaldehyde and fluorescamine. Chemiluminescent labels of use may include luminol, isoluminol, an aromatic acridinium ester, an imidazole, an acridinium salt or an oxalate ester. 
     Methods of Therapeutic Treatment 
     The claimed methods and compositions are of use for treating disease states, such as B-cell lymphomas or leukemias, autoimmune disease or immune system dysfunction (e.g., graft-versus-host disease). The methods may comprise administering a therapeutically effective amount of an anti-CD74 antibody or fragment thereof or immunoconjugate, either alone or in combination with one or more other therapeutic agents, administered either concurrently or sequentially. In preferred embodiments, as described in the Examples below, the anti-CD74 antibody or fragment thereof may be administered in the form of a DNL complex in combination with one or more other therapeutic agents, such as a second antibody or fragment thereof. 
     Multimodal therapies may include therapy with other antibodies, such as antibodies against CD4, CD5, CD8, CD14, CD15, CD19, CD20, CD21, CD22, CD23, CD25, CD33, CD37, CD38, CD40, CD40L, CD46, CD52, CD54, CD74, CD80, CD126, CD138, CXCR4, B7, HM1.24, HLA-DR, an angiogenesis factor, tenascin, VEGF, PIGF, ED-B fibronectin, an oncogene, an oncogene product, NCA 66a-d, necrosis antigens, Ii, IL-2, T101, TAC, IL-6, MUC-1, TRAIL-R1 (DR4) or TRAIL-R2 (DR5) in the form of naked antibodies, fusion proteins, or as immunoconjugates. Various antibodies of use are known to those of skill in the art. See, for example, Ghetie et al.,  Cancer Res.  48:2610 (1988); Hekman et al.,  Cancer Immunol. Immunother.  32:364 (1991); Longo,  Curr. Opin. Oncol.  8:353 (1996), U.S. Pat. Nos. 5,798,554; 6,187,287; 6,306,393; 6,676,924; 7,109,304; 7,151,164; 7,230,084; 7,230,085; 7,238,785; 7,238,786; 7,282,567; 7,300,655; 7,312,318; 7,612,180; 7,501,498; the Examples section of each of which is incorporated herein by reference. 
     In another form of multimodal therapy, subjects may receive therapeutic anti-CD74 antibodies or antibody combinations in conjunction with standard chemotherapy. For example, “CVB” (1.5 g/m 2  cyclophosphamide, 200-400 mg/m 2  etoposide, and 150-200 mg/m 2  carmustine) is a regimen used to treat non-Hodgkin&#39;s lymphoma. Patti et al., Eur.  J. Haematol.  51: 18 (1993). Other suitable combination chemotherapeutic regimens are well-known to those of skill in the art. See, for example, Freedman et al., “Non-Hodgkin&#39;s Lymphomas,” in CANCER MEDICINE, VOLUME 2, 3rd Edition, Holland et al. (eds.), pages 2028-2068 (Lea &amp; Febiger 1993). As an illustration, first generation chemotherapeutic regimens for treatment of intermediate-grade non-Hodgkin&#39;s lymphoma (NHL) include C-MOPP (cyclophosphamide, vincristine, procarbazine and prednisone) and CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone). A useful second generation chemotherapeutic regimen is m-BACOD (methotrexate, bleomycin, doxorubicin, cyclophosphamide, vincristine, dexamethasone and leucovorin), while a suitable third generation regimen is MACOP-B (methotrexate, doxorubicin, cyclophosphamide, vincristine, prednisone, bleomycin and leucovorin). Additional useful drugs include phenyl butyrate, bendamustine, and bryostatin-1. 
     Therapeutic antibodies or complexes, such as DNL complexes, can be formulated according to known methods to prepare pharmaceutically useful compositions, whereby the therapeutic antibody complex is combined in a mixture with a pharmaceutically suitable excipient. Sterile phosphate-buffered saline is one example of a pharmaceutically suitable excipient. Other suitable excipients are well-known to those in the art. See, for example, Ansel et al., PHARMACEUTICAL DOSAGE FORMS AND DRUG DELIVERY SYSTEMS, 5th Edition (Lea &amp; Febiger 1990), and Gennaro (ed.), REMINGTON&#39;S PHARMACEUTICAL SCIENCES, 18th Edition (Mack Publishing Company 1990), and revised editions thereof. 
     The therapeutic antibody complex can be formulated for intravenous administration via, for example, bolus injection or continuous infusion. Preferably, the therapeutic antibody complex is infused over a period of less than about 4 hours, and more preferably, over a period of less than about 3 hours. For example, the first 25-50 mg could be infused within 30 minutes, preferably even 15 min, and the remainder infused over the next 2-3 hrs. Formulations for injection can be presented in unit dosage form, e.g., in ampoules or in multi-dose containers, with an added preservative. The compositions can take such forms as suspensions, solutions or emulsions in oily or aqueous vehicles, and can contain formulatory agents such as suspending, stabilizing and/or dispersing agents. Alternatively, the active ingredient can be in powder form for constitution with a suitable vehicle, e.g., sterile pyrogen-free water, before use. 
     The therapeutic antibody complex may also be administered to a mammal subcutaneously or even by other parenteral routes. Moreover, the administration may be by continuous infusion or by single or multiple boluses. In most preferred embodiments, the therapeutic antibody or combination is administered subcutaneously in a volume of 1, 2 or 3 ml and at a concentration of at least 80 mg/ml, at least 100 mg/ml, at least 125 mg/ml, at least 150 mg/ml, at least 200 mg/ml, at least 250 mg/ml or at least 300 mg/ml. Methods of antibody concentration and subcutaneous formulations are disclosed in provisional U.S. Patent No. 61/509,850, filed Jul. 20, 2011, the Examples section of which (from paragraph 0133, page 48 to paragraph 0195, page 64) is incorporated herein by reference. 
     More generally, the dosage of an administered therapeutic antibody complex for humans will vary depending upon such factors as the patient&#39;s age, weight, height, sex, general medical condition and previous medical history. It may be desirable to provide the recipient with a dosage of therapeutic antibody complex that is in the range of from about 1 mg/kg to 25 mg/kg as a single intravenous infusion, although a lower or higher dosage also may be administered as circumstances dictate. A dosage of 1-20 mg/kg for a 70 kg patient, for example, is 70-1,400 mg, or 41-824 mg/m 2  for a 1.7-m patient. The dosage may be repeated as needed, for example, once per week for 4-10 weeks, once per week for 8 weeks, or once per week for 4 weeks. It may also be given less frequently, such as every other week for several months, or monthly or quarterly for many months, as needed in a maintenance therapy. 
     Alternatively, a therapeutic antibody complex may be administered as one dosage every 2 or 3 weeks, repeated for a total of at least 3 dosages. Or, the therapeutic antibody complex may be administered twice per week for 4-6 weeks. If the dosage is lowered to approximately 200-300 mg/m 2  (340 mg per dosage for a 1.7-m patient, or 4.9 mg/kg for a 70 kg patient), it may be administered once or even twice weekly for 4 to 10 weeks. Alternatively, the dosage schedule may be decreased, namely every 2 or 3 weeks for 2-3 months. It has been determined, however, that even higher doses, such as 20 mg/kg once weekly or once every 2-3 weeks can be administered by slow i.v. infusion, for repeated dosing cycles. The dosing schedule can optionally be repeated at other intervals and dosage may be given through various parenteral routes, with appropriate adjustment of the dose and schedule. 
     Additional pharmaceutical methods may be employed to control the duration of action of the therapeutic immunoconjugate or naked antibody. Control release preparations can be prepared through the use of polymers to complex or adsorb the antibody. For example, biocompatible polymers include matrices of poly(ethylene-co-vinyl acetate) and matrices of a polyanhydride copolymer of a stearic acid dimer and sebacic acid. Sherwood et al., Bio/Technology 10: 1446 (1992). The rate of release of an antibody from such a matrix depends upon the molecular weight of the antibody, the amount of antibody within the matrix, and the size of dispersed particles. Saltzman et al., Biophys. J. 55: 163 (1989); Sherwood et al., supra. Other solid dosage forms are described in Ansel et al., PHARMACEUTICAL DOSAGE FORMS AND DRUG DELIVERY SYSTEMS, 5th Edition (Lea &amp; Febiger 1990), and Gennaro (ed.), REMINGTON&#39;S PHARMACEUTICAL SCIENCES, 18th Edition (Mack Publishing Company 1990), and revised editions thereof. 
     Cancer Therapy 
     In preferred embodiments, the anti-CD74 antibodies, combinations or complexes are of use for therapy of cancer. Examples of cancers include, but are not limited to, carcinoma, lymphoma, glioblastoma, melanoma, sarcoma, and leukemia, myeloma, or lymphoid malignancies. More particular examples of such cancers are noted below and include: squamous cell cancer (e.g., epithelial squamous cell cancer), Ewing sarcoma, Wilms tumor, astrocytomas, lung cancer including small-cell lung cancer, non-small cell lung cancer, adenocarcinoma of the lung and squamous carcinoma of the lung, cancer of the peritoneum, hepatocellular cancer, gastric or stomach cancer including gastrointestinal cancer, pancreatic cancer, glioblastoma multiforme, cervical cancer, ovarian cancer, liver cancer, bladder cancer, hepatoma, hepatocellular carcinoma, neuroendocrine tumors, medullary thyroid cancer, differentiated thyroid carcinoma, breast cancer, ovarian cancer, colon cancer, rectal cancer, endometrial cancer or uterine carcinoma, salivary gland carcinoma, kidney or renal cancer, prostate cancer, vulvar cancer, anal carcinoma, penile carcinoma, as well as head-and-neck cancer. The term “cancer” includes primary malignant cells or tumors (e.g., those whose cells have not migrated to sites in the subject&#39;s body other than the site of the original malignancy or tumor) and secondary malignant cells or tumors (e.g., those arising from metastasis, the migration of malignant cells or tumor cells to secondary sites that are different from the site of the original tumor). 
     Other examples of cancers or malignancies include, but are not limited to: Acute Childhood Lymphoblastic Leukemia, Acute Lymphoblastic Leukemia, Acute Lymphocytic Leukemia, Acute Myeloid Leukemia, Adrenocortical Carcinoma, Adult (Primary) Hepatocellular Cancer, Adult (Primary) Liver Cancer, Adult Acute Lymphocytic Leukemia, Adult Acute Myeloid Leukemia, Adult Hodgkin&#39;s Lymphoma, Adult Lymphocytic Leukemia, Adult Non-Hodgkin&#39;s Lymphoma, Adult Primary Liver Cancer, Adult Soft Tissue Sarcoma, AIDS-Related Lymphoma, AIDS-Related Malignancies, Anal Cancer, Astrocytoma, Bile Duct Cancer, Bladder Cancer, Bone Cancer, Brain Stem Glioma, Brain Tumors, Breast Cancer, Cancer of the Renal Pelvis and Ureter, Central Nervous System (Primary) Lymphoma, Central Nervous System Lymphoma, Cerebellar Astrocytoma, Cerebral Astrocytoma, Cervical Cancer, Childhood (Primary) Hepatocellular Cancer, Childhood (Primary) Liver Cancer, Childhood Acute Lymphoblastic Leukemia, Childhood Acute Myeloid Leukemia, Childhood Brain Stem Glioma, Childhood Cerebellar Astrocytoma, Childhood Cerebral Astrocytoma, Childhood Extracranial Germ Cell Tumors, Childhood Hodgkin&#39;s Disease, Childhood Hodgkin&#39;s Lymphoma, Childhood Hypothalamic and Visual Pathway Glioma, Childhood Lymphoblastic Leukemia, Childhood Medulloblastoma, Childhood Non-Hodgkin&#39;s Lymphoma, Childhood Pineal and Supratentorial Primitive Neuroectodermal Tumors, Childhood Primary Liver Cancer, Childhood Rhabdomyosarcoma, Childhood Soft Tissue Sarcoma, Childhood Visual Pathway and Hypothalamic Glioma, Chronic Lymphocytic Leukemia, Chronic Myelogenous Leukemia, Colon Cancer, Cutaneous T-Cell Lymphoma, Endocrine Pancreas Islet Cell Carcinoma, Endometrial Cancer, Ependymoma, Epithelial Cancer, Esophageal Cancer, Ewing&#39;s Sarcoma and Related Tumors, Exocrine Pancreatic Cancer, Extracranial Germ Cell Tumor, Extragonadal Germ Cell Tumor, Extrahepatic Bile Duct Cancer, Eye Cancer, Female Breast Cancer, Gaucher&#39;s Disease, Gallbladder Cancer, Gastric Cancer, Gastrointestinal Carcinoid Tumor, Gastrointestinal Tumors, Germ Cell Tumors, Gestational Trophoblastic Tumor, Hairy Cell Leukemia, Head and Neck Cancer, Hepatocellular Cancer, Hodgkin&#39;s Lymphoma, Hypergammaglobulinemia, Hypopharyngeal Cancer, Intestinal Cancers, Intraocular Melanoma, Islet Cell Carcinoma, Islet Cell Pancreatic Cancer, Kaposi&#39;s Sarcoma, Kidney Cancer, Laryngeal Cancer, Lip and Oral Cavity Cancer, Liver Cancer, Lung Cancer, Lymphoproliferative Disorders, Macroglobulinemia, Male Breast Cancer, Malignant Mesothelioma, Malignant Thymoma, Medulloblastoma, Melanoma, Mesothelioma, Metastatic Occult Primary Squamous Neck Cancer, Metastatic Primary Squamous Neck Cancer, Metastatic Squamous Neck Cancer, Multiple Myeloma, Multiple Myeloma/Plasma Cell Neoplasm, Myelodysplastic Syndrome, Myelogenous Leukemia, Myeloid Leukemia, Myeloproliferative Disorders, Nasal Cavity and Paranasal Sinus Cancer, Nasopharyngeal Cancer, Neuroblastoma, Non-Hodgkin&#39;s Lymphoma, Nonmelanoma Skin Cancer, Non-Small Cell Lung Cancer, Occult Primary Metastatic Squamous Neck Cancer, Oropharyngeal Cancer, Osteo-/Malignant Fibrous Sarcoma, Osteosarcoma/Malignant Fibrous Histiocytoma, Osteosarcoma/Malignant Fibrous Histiocytoma of Bone, Ovarian Epithelial Cancer, Ovarian Germ Cell Tumor, Ovarian Low Malignant Potential Tumor, Pancreatic Cancer, Paraproteinemias, Polycythemia vera, Parathyroid Cancer, Penile Cancer, Pheochromocytoma, Pituitary Tumor, Primary Central Nervous System Lymphoma, Primary Liver Cancer, Prostate Cancer, Rectal Cancer, Renal Cell Cancer, Renal Pelvis and Ureter Cancer, Retinoblastoma, Rhabdomyosarcoma, Salivary Gland Cancer, Sarcoidosis Sarcomas, Sezary Syndrome, Skin Cancer, Small Cell Lung Cancer, Small Intestine Cancer, Soft Tissue Sarcoma, Squamous Neck Cancer, Stomach Cancer, Supratentorial Primitive Neuroectodermal and Pineal Tumors, T-Cell Lymphoma, Testicular Cancer, Thymoma, Thyroid Cancer, Transitional Cell Cancer of the Renal Pelvis and Ureter, Transitional Renal Pelvis and Ureter Cancer, Trophoblastic Tumors, Ureter and Renal Pelvis Cell Cancer, Urethral Cancer, Uterine Cancer, Uterine Sarcoma, Vaginal Cancer, Visual Pathway and Hypothalamic Glioma, Vulvar Cancer, Waldenstrom&#39;s Macroglobulinemia, Wilms&#39; Tumor, and any other hyperproliferative disease, besides neoplasia, located in an organ system listed above. 
     The methods and compositions described and claimed herein may be used to treat malignant or premalignant conditions and to prevent progression to a neoplastic or malignant state, including but not limited to those disorders described above. Such uses are indicated in conditions known or suspected of preceding progression to neoplasia or cancer, in particular, where non-neoplastic cell growth consisting of hyperplasia, metaplasia, or most particularly, dysplasia has occurred (for review of such abnormal growth conditions, see Robbins and Angell, Basic Pathology, 2d Ed., W. B. Saunders Co., Philadelphia, pp. 68-79 (1976)). 
     Dysplasia is frequently a forerunner of cancer, and is found mainly in the epithelia. It is the most disorderly form of non-neoplastic cell growth, involving a loss in individual cell uniformity and in the architectural orientation of cells. Dysplasia characteristically occurs where there exists chronic irritation or inflammation. Dysplastic disorders which can be treated include, but are not limited to, anhidrotic ectodermal dysplasia, anterofacial dysplasia, asphyxiating thoracic dysplasia, atriodigital dysplasia, bronchopulmonary dysplasia, cerebral dysplasia, cervical dysplasia, chondroectodermal dysplasia, cleidocranial dysplasia, congenital ectodermal dysplasia, craniodiaphysial dysplasia, craniocarpotarsal dysplasia, craniometaphysial dysplasia, dentin dysplasia, diaphysial dysplasia, ectodermal dysplasia, enamel dysplasia, encephalo-ophthalmic dysplasia, dysplasia epiphysialis hemimelia, dysplasia epiphysialis multiplex, dysplasia epiphysialis punctata, epithelial dysplasia, faciodigitogenital dysplasia, familial fibrous dysplasia of jaws, familial white folded dysplasia, fibromuscular dysplasia, fibrous dysplasia of bone, florid osseous dysplasia, hereditary renal-retinal dysplasia, hidrotic ectodermal dysplasia, hypohidrotic ectodermal dysplasia, lymphopenic thymic dysplasia, mammary dysplasia, mandibulofacial dysplasia, metaphysial dysplasia, Mondini dysplasia, monostotic fibrous dysplasia, mucoepithelial dysplasia, multiple epiphysial dysplasia, oculoauriculovertebral dysplasia, oculodentodigital dysplasia, oculovertebral dysplasia, odontogenic dysplasia, opthalmomandibulomelic dysplasia, periapical cemental dysplasia, polyostotic fibrous dysplasia, pseudoachondroplastic spondyloepiphysial dysplasia, retinal dysplasia, septo-optic dysplasia, spondyloepiphysial dysplasia, and ventriculoradial dysplasia. 
     Additional pre-neoplastic disorders which can be treated include, but are not limited to, benign dysproliferative disorders (e.g., benign tumors, fibrocystic conditions, tissue hypertrophy, intestinal polyps or adenomas, and esophageal dysplasia), leukoplakia, keratoses, Bowen&#39;s disease, Farmer&#39;s Skin, solar cheilitis, and solar keratosis. 
     In preferred embodiments, the method of the invention is used to inhibit growth, progression, and/or metastasis of cancers, in particular those listed above. 
     Additional hyperproliferative diseases, disorders, and/or conditions include, but are not limited to, progression, and/or metastases of malignancies and related disorders such as leukemia (including acute leukemias (e.g., acute lymphocytic leukemia, acute myelocytic leukemia (including myeloblastic, promyelocytic, myelomonocytic, monocytic, and erythroleukemia)) and chronic leukemias (e.g., chronic myelocytic (granulocytic) leukemia and chronic lymphocytic leukemia)), polycythemia vera, lymphomas (e.g., Hodgkin&#39;s disease and non-Hodgkin&#39;s disease), multiple myeloma, Waldenstrom&#39;s macroglobulinemia, heavy chain disease, and solid tumors including, but not limited to, sarcomas and carcinomas such as fibrosarcoma, myxosarcoma, liposarcoma, chondrosarcoma, osteogenic sarcoma, chordoma, angiosarcoma, endotheliosarcoma, lymphangiosarcoma, lymphangioendotheliosarcoma, synovioma, mesothelioma, Ewing&#39;s tumor, leiomyosarcoma, rhabdomyosarcoma, colon carcinoma, pancreatic cancer, breast cancer, ovarian cancer, prostate cancer, squamous cell carcinoma, basal cell carcinoma, adenocarcinoma, sweat gland carcinoma, sebaceous gland carcinoma, papillary carcinoma, papillary adenocarcinomas, cystadenocarcinoma, medullary carcinoma, bronchogenic carcinoma, renal cell carcinoma, hepatoma, bile duct carcinoma, choriocarcinoma, seminoma, embryonal carcinoma, Wilm&#39;s tumor, cervical cancer, testicular tumor, lung carcinoma, small cell lung carcinoma, bladder carcinoma, epithelial carcinoma, glioma, astrocytoma, medulloblastoma, craniopharyngioma, ependymoma, pinealoma, emangioblastoma, acoustic neuroma, oligodendroglioma, meningioma, melanoma, neuroblastoma, and retinoblastoma. 
     Therapy of Autoimmune Disease 
     The subject anti-CD74 antibodies, combinations or complexes thereof can be used to treat immune dysregulation disease and related autoimmune diseases. Immune diseases may include acute immune thrombocytopenia, Addison&#39;s disease, adult respiratory distress syndrome (ARDS), agranulocytosis, allergic conditions, allergic encephalomyelitis, allergic neuritis, amyotrophic lateral sclerosis (ALS), ankylosing spondylitis, antigen-antibody complex mediated diseases, anti-glomerular basement membrane disease, anti-phospholipid antibody syndrome, aplastic anemia, arthritis, asthma, atherosclerosis, autoimmune disease of the testis and ovary, autoimmune endocrine diseases, autoimmune myocarditis, autoimmune neutropenia, autoimmune polyendocrinopathies, autoimmune polyglandular syndromes (or polyglandular endocrinopathy syndromes), autoimmune thrombocytopenia, Bechet disease, Berger&#39;s disease (IgA nephropathy), bronchiolitis obliterans (non-transplant), bullous pemphigoid, pemphigus vulgaris, Castleman&#39;s syndrome, Celiac sprue (gluten enteropathy), central nervous system (CNS) inflammatory disorders, chronic active hepatitis, chronic immune thrombocytopenia dermatomyositis, colitis, conditions involving infiltration of T cells and chronic inflammatory responses, coronary artery disease, Crohn&#39;s disease, cryoglobulinemia, dermatitis, dermatomyositis, diabetes mellitus, diseases involving leukocyte diapedesis, eczema, encephalitis, erythema multiforme, erythema nodosum, Factor VIII deficiency, fibrosing alveolitis, giant cell arteritis, glomerulonephritis, Goodpasture&#39;s syndrome, graft versus host disease (GVHD), granulomatosis, Grave&#39;s disease, Guillain-Barre Syndrome, Hashimoto&#39;s thyroiditis, hemophilia A, Henoch-Schonlein purpura, idiopathic hypothyroidism, immune thrombocytopenia (ITP), IgA nephropathy, IgA nephropathy, IgM mediated neuropathy, immune complex nephritis, immune hemolytic anemia including autoimmune hemolytic anemia (AIHA), immune responses associated with acute and delayed hypersensitivity mediated by cytokines and T-lymphocytes, immune-mediated thrombocytopenias, juvenile onset diabetes, juvenile rheumatoid arthritis, Lambert-Eaton Myasthenic Syndrome, large vessel vasculitis, leukocyte adhesion deficiency, leukopenia, lupus nephritis, lymphoid interstitial pneumonitis (HIV), medium vessel vasculitis, membranous nephropathy, meningitis, multiple organ injury syndrome, multiple sclerosis, myasthenia gravis, osteoarthritis, pancytopenia, pemphigoid bullous, pemphigus vulgaris, pernicious anemia, polyarteritis nodosa, polychondritis, polyglandular syndromes, polymyalgia, polymyositis, post-streptococcal nephritis, primary biliary cirrhosis, primary hypothyroidism, psoriasis, psoriatic arthritis, pure red cell aplasia (PRCA), rapidly progressive glomerulonephritis, Reiter&#39;s disease, respiratory distress syndrome, responses associated with inflammatory bowel disease, Reynaud&#39;s syndrome, rheumatic fever, rheumatoid arthritis, sarcoidosis, scleroderma, Sjogren&#39;s syndrome, solid organ transplant rejection, Stevens-Johnson syndrome, stiff-man syndrome, subacute thyroiditis, Sydenham&#39;s chorea, systemic lupus erythematosus (SLE), systemic scleroderma and sclerosis, tabes dorsalis, Takayasu&#39;s arteritis, thromboangitis obliterans, thrombotic thrombocytopenic purpura (TTP), thyrotoxicosis, toxic epidermal necrolysis, tuberculosis, Type I diabetes, ulcerative colitis, uveitis, vasculitis (including ANCA) and Wegener&#39;s granulomatosis. 
     Type-1 and Type-2 diabetes may be treated using known antibodies against B-cell antigens, such as CD22 (epratuzumab), CD74 (milatuzumab), CD19 (hA19), CD20 (veltuzumab) or HLA-DR (hL243) (see, e.g., Winer et al., 2011, Nature Med 17:610-18). Anti-CD3 antibodies also have been proposed for therapy of type 1 diabetes (Cernea et al., 2010, Diabetes Metab Rev 26:602-05). 
     Kits 
     Various embodiments may concern kits containing anti-CD74 antibodies, antibody combinations and/or antibody constructs and/or other components. Such components may include a targetable construct. In alternative embodiments it is contemplated that a targetable construct may be attached to one or more different therapeutic and/or diagnostic agents. 
     If the composition containing components for administration is not formulated for delivery via the alimentary canal, such as by oral delivery, a device capable of delivering the kit components through some other route may be included. One type of device, for applications such as parenteral delivery, is a syringe that is used to inject the composition into the body of a subject. Inhalation devices may also be used for certain applications. 
     The kit components may be packaged together or separated into two or more containers. In some embodiments, the containers may be vials that contain sterile, lyophilized formulations of a composition that are suitable for reconstitution. A kit may also contain one or more buffers suitable for reconstitution and/or dilution of other reagents. Other containers that may be used include, but are not limited to, a pouch, tray, box, tube, or the like. Kit components may be packaged and maintained sterilely within the containers. Another component that can be included is instructions to a person using a kit for its use. 
     EXAMPLES 
     Various embodiments of the present invention are illustrated by the following examples, without limiting the scope thereof. 
     Example 1 
     Preparation of hLL1, hLL2, hA20 and hL243 Antibodies 
     The hLL1, hLL2, hA20 and hL243 antibodies were prepared as previously described and as summarized below. The constant region sequences of each of the hLL1, hLL2, hA20 and hL243 antibodies are as shown below in SEQ ID NO:144 (heavy chain constant region amino acid sequence); SEQ ID NO:145 (heavy chain constant region DNA sequence); SEQ ID NO:146 (light chain constant region amino acid sequence); and SEQ ID NO:147 (light chain constant region amino acid sequence). Although the constant region sequences are derived from the hLL2 antibody, they are identical in each of hLL1, hLL2, hA20 and hL243. Therefore, each of the hLL1, hLL2, hA20 and hL243 antibodies is a Glm3 allotype antibody. 
     
       
         
           
               
            
               
                 Heavy chain constant region amino acid sequence  
               
               
                 (CH1-Hinge-CH2-CH3) 
               
               
                 (SEQ ID NO: 144) 
               
               
                 ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGV 
               
               
                   
               
               
                 HTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKRVEP 
               
               
                   
               
               
                 KSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVS 
               
               
                   
               
               
                 HEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGK 
               
               
                   
               
               
                 EYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQVSLTC 
               
               
                   
               
               
                 LVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRW 
               
               
                   
               
               
                 QQGNVFSCSVMHEALHNHYTQKSLSLSPGK  
               
               
                   
               
               
                 Heavy chain constant region DNA sequence 
               
               
                 (SEQ ID NO: 145) 
               
               
                 GCCTCCACCAAGGGCCCATCGGTCTTCCCCCTGGCACCCTCCTCCAAGAG 
               
               
                   
               
               
                 CACCTCTGGGGGCACAGCGGCCCTGGGCTGCCTGGTCAAGGACTACTTCC 
               
               
                   
               
               
                 CCGAACCGGTGACGGTGTCGTGGAACTCAGGCGCCCTGACCAGCGGCGTG 
               
               
                   
               
               
                 CACACCTTCCCGGCTGTCCTACAGTCCTCAGGACTCTACTCCCTCAGCAG 
               
               
                   
               
               
                 CGTGGTGACCGTGCCCTCCAGCAGCTTGGGCACCCAGACCTACATCTGCA 
               
               
                   
               
               
                 ACGTGAATCACAAGCCCAGCAACACCAAGGTGGACAAGAGAGTTGAGCCC 
               
               
                   
               
               
                 AAATCTTGTGACAAAACTCACACATGCCCACCGTGCCCAGCACCTGAACT 
               
               
                   
               
               
                 CCTGGGGGGACCGTCAGTCTTCCTCTTCCCCCCAAAACCCAAGGACACCC 
               
               
                   
               
               
                 TCATGATCTCCCGGACCCCTGAGGTCACATGCGTGGTGGTGGACGTGAGC 
               
               
                   
               
               
                 CACGAAGACCCTGAGGTCAAGTTCAACTGGTACGTGGACGGCGTGGAGGT 
               
               
                   
               
               
                 GCATAATGCCAAGACAAAGCCGCGGGAGGAGCAGTACAACAGCACGTACC 
               
               
                   
               
               
                 GGGTGGTCAGCGTCCTCACCGTCCTGCACCAGGACTGGCTGAATGGCAAG 
               
               
                   
               
               
                 GAGTACAAGTGCAAGGTCTCCAACAAAGCCCTCCCAGCCCCCATCGAGAA 
               
               
                   
               
               
                 AACCATCTCCAAAGCCAAAGGGCAGCCCCGAGAACCACAGGTGTACACCC 
               
               
                   
               
               
                 TGCCCCCATCCCGGGAGGAGATGACCAAGAACCAGGTCAGCCTGACCTGC 
               
               
                   
               
               
                 CTGGTCAAAGGCTTCTATCCCAGCGACATCGCCGTGGAGTGGGAGAGCAA 
               
               
                   
               
               
                 TGGGCAGCCGGAGAACAACTACAAGACCACGCCTCCCGTGCTGGACTCCG 
               
               
                   
               
               
                 ACGGCTCCTTCTTCCTCTATAGCAAGCTCACCGTGGACAAGAGCAGGTGG 
               
               
                   
               
               
                 CAGCAGGGGAACGTCTTCTCATGCTCCGTGATGCATGAGGCTCTGCACAA 
               
               
                   
               
               
                 CCACTACACGCAGAAGAGCCTCTCCCTGTCTCCGGGTAAA  
               
               
                   
               
               
                 Light chain constant region amino acid sequence 
               
               
                 (SEQ ID NO: 146) 
               
               
                 TVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQSGN 
               
               
                   
               
               
                 SQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYACEVTHQGLSSPVTKS 
               
               
                   
               
               
                 FNRGEC  
               
               
                   
               
               
                 Light chain constant region DNA sequence 
               
               
                 (SEQ ID NO: 147) 
               
               
                 ACTGTGGCTGCACCATCTGTCTTCATCTTCCCGCCATCTGATGAGCAGTT 
               
               
                   
               
               
                 GAAATCTGGAACTGCCTCTGTTGTGTGCCTGCTGAATAACTTCTATCCCA 
               
               
                   
               
               
                 GAGAGGCCAAAGTACAGTGGAAGGTGGATAACGCCCTCCAATCGGGTAAC 
               
               
                   
               
               
                 TCCCAGGAGAGTGTCACAGAGCAGGACAGCAAGGACAGCACCTACAGCCT 
               
               
                   
               
               
                 CAGCAGCACCCTGACGCTGAGCAAAGCAGACTACGAGAAACACAAAGTCT 
               
               
                   
               
               
                 ACGCCTGCGAAGTCACCCATCAGGGCCTGAGCTCGCCCGTCACAAAGAGC 
               
               
                   
               
               
                 TTCAACAGGGGAGAGTGT  
               
            
           
         
       
     
     hLL1 Antibody 
     The hLL1 anti-CD74 antibody was prepared as described in U.S. Pat. No. 7,772,373 (incorporated by reference from Col. 3, line 54 to Col. 5, line 32 and Col. 34, line 15 to Col. 40, line 45,  FIGS. 1A, 1B, 2A, 2B, 3A, 3B, 4A, 4B ). The variable region sequences of the light and heavy chains of the hLL1 antibody are as described in U.S. Pat. No. 7,772,373 (e.g.,  FIG. 3  and  FIG. 4 ). 
     A modified strategy as described by Leung et al. (1994, Hybridoma 13:469-76) was used to construct the VK and VH genes for hLL1 using a combination of long oligonucleotide synthesis and PCR. For the construction of the hLL1 VH domain, two long oligonucleotides, hLL1VHA (176 mer) and hLL1VHB (165-mer) (U.S. Pat. No. 7,772,373) were synthesized on an automated DNA synthesizer. The hLL1VHA sequence represented nt 20 to 195 of the hLL1VH domain. The hLL1 VHB sequence represented the minus strand of the hLL1 VH domain complementary to nt 173 to 337. The 3′-terminal sequences (22 nt residues) of hLL1VHA and B were complementary to each other. Under PCR condition, the 3′-ends of hLL1 VHA and B annealed to form a short double stranded DNA. Each annealed end served as a primer for the transcription of single stranded DNA, resulting in a double strand DNA composed of the nt 20 to 337 of hLL1VH. This DNA was further amplified in the presence of two short oligonucleotides, hLL1VHBACK and hLL1VHFOR (U.S. Pat. No. 7,772,373) to form the full-length hLL1VH. Double-stranded PCR-amplified product for hLL1VH was gel-purified, restriction-digested with PstI and BstEII and cloned into the complementary PstI/BstEII sites of the heavy chain staging vector, VHpB S2. 
     For constructing the full length DNA of the humanized VK sequence, hLL1VKA (159-mer) and hLL1VKB (169-mer) (U.S. Pat. No. 7,772,373) were synthesized. The hLL1 VKA sequence represented nt 16 to 174 of the hLL1VK domain. The hLL1VKB sequence represented the minus strand of the hLL1VK domain complementary to nt 153 to 321. hLL1VKA and B were amplified by two short oligonucleotides hLL1VKBACK and hLL1VKFOR (U.S. Pat. No. 7,772,373) to form double-stranded DNA. Further amplification produced the full length VK gene (U.S. Pat. No. 7,772,373). Gel-purified PCR products for hLL1VK were restriction-digested with PvuII and BglIII and cloned into the complementary PvuI/BclI sites of the light chain staging vector, VKpBR2. 
     The final expression vector hLL1pdHL2 was constructed by sequentially subcloning the XbaI-BamHI and XhoI/BamHI fragments of hLL1VK and VH, respectively, into pdHL2. The pdHL2 vector is known in the art (see, e.g., Gillies et al., 1989, J Immunol Methods 125:191). The pdHL2 vector provides expression of both IgG heavy and light chain genes that are independently controlled by two metallothionine promoters and IgH enhancers. Use of pdHL2 as an expression vector for antibody production has been disclosed, for example, in Losman et al., 1999, Clin Cancer Res 5:3101s-05s. 
     The fragment containing the VK sequence of hLL1, together with the signal peptide sequence, was excised from LL1VKpBR2 by double restriction digestion with XbaI and BamHI. The ˜550 bp VK fragment was then subcloned into the XbaI/BamHI site of a mammalian expression vector, pdHL2. The resulting vector was designated as hLL1VKpdHL2. Similarly, the ˜750 bp fragment encoding hLL1 VH, together with the signal peptide sequence, was excised from LL1VHpBS2 by XhoI and BamHI digestion and isolated by electrophoresis in an agarose gel. The fragment was subcloned into the XhoI and HindIII site of hLL1VKpdHL2 with the aid of linker comparable to both BamHI and HindIII ends, resulting in the final expression vector, designated as hLL1pdHL2. 
     Approximately 30 μg of hLL1pdHL2 was linearized by digestion with Sal I and transfected into Sp2/0-Ag14 cells by electroporation. The transfected cells were plated into 96-well plate for 2 days and then selected for MTX resistance. Supernatants from colonies surviving selection were monitored for chimeric antibody secretion by ELISA assay. Positive cell clones were expanded and hLL1 was purified from cell culture supernatant. 
     hLL2 Antibody 
     The hLL2 anti-CD22 antibody was prepared as described in U.S. Pat. No. 6,187,287 (incorporated by reference from Col. 3, line 35 to Col. 4, line 34 and Col. 11, line 40 to Col. 20, line 38,  FIGS. 1, 4A, 4B, 5A, 5B ). The variable region sequences of the light and heavy chains of the hLL2 antibody are as described in U.S. Pat. No. 6,187,287 (e.g.,  FIG. 1 ,  FIG. 5 ). The LL2 antibody was deposited on May 27, 2005, with the American Type Culture Collection, Manassas, Va. (ATCC Accession No. PTA-6735), formerly the EPB-2 monoclonal antibody, which was produced against human Raji cells derived from a Burkitt lymphoma. (Pawlak-Byczkowska et al., 1989, Cancer Res. 49:4568.) The cloning, transfection and protein production were performed as described above for the hLL1 antibody. 
     hA20 Antibody 
     The hA20 anti-CD20 antibody was prepared as described in U.S. Pat. No. 7,919,273 (incorporated by reference from Col. 7, line 25 to Col. 9, line 4 and Col. 34, line 15 to Col. 72, line 2,  FIGS. 1A, 1B, 2A, 2B, 3A, 3B ). The variable region sequences of the light and heavy chains of the hA20 antibody are as described in U.S. Pat. No. 7,919,273 (e.g.,  FIG. 2 ,  FIG. 3 ). The cloning, transfection and protein production were performed as described above for the hLL1 antibody. 
     hL243 Antibody 
     The hL243 anti-HLA-DR antibody was prepared as described in U.S. Pat. No. 7,612,180 (incorporated by reference from Col. 4, line 16 to Col. 6, line 38 and Col. 46, line 50 to Col. 60, line 67,  FIGS. 1 to 6 ). The variable region sequences of the light and heavy chains of the hL243 antibody are as described in U.S. Pat. No. 7,612,180 (e.g.,  FIG. 3 ,  FIG. 4 ,  FIG. 5 ,  FIG. 6 ). The cloning, transfection and protein production were performed as described above for the hLL1 antibody. 
     Other known antibodies, such as hPAM4 (U.S. Pat. No. 7,282,567), hAl9 (U.S. Pat. No. 7,109,304), hIMMU31 (U.S. Pat. No. 7,300,655), hMu-9 (U.S. Pat. No. 7,387,773), hMN-14 (U.S. Pat. No. 6,676,924), hMN-15 (U.S. Pat. No. 7,541,440), hRl (U.S. patent application Ser. No. 12/689,336), hRS7 (U.S. Pat. No. 7,238,785), hMN-3 (U.S. Pat. No. 7,541,440), 15B8 (anti-CD40, U.S. Pat. No. 7,820,170), AB-PG1-XG1-026 (U.S. patent application Ser. No. 11/983,372, deposited as ATCC PTA-4405 and PTA-4406) and D2/B (WO 2009/130575), may be prepared as described above, using the techniques disclosed herein. 
     Example 2 
     Preparation of Dock-and-Lock (DNL) Constructs 
     DDD and AD Fusion Proteins 
     The DNL technique can be used to make dimers, trimers, tetramers, hexamers, etc. comprising virtually any antibody, antibody fragment, immunomodulator, cytokine, enzyme, peptide, PEG moiety, toxin, xenoantigen or other effector moiety. For certain preferred embodiments, antibodies, cytokines or toxins (such as ranpirnase) may be produced as fusion proteins comprising either a dimerization and docking domain (DDD) or anchoring domain (AD) sequence. Although in preferred embodiments the DDD and AD moieties may be joined to antibodies, antibody fragments, cytokines, toxins or other effector moieties as fusion proteins, the skilled artisan will realize that other methods of conjugation exist, such as chemical cross-linking, click chemistry reaction, etc. 
     The technique is not limiting and any protein or peptide of use may be produced as an AD or DDD fusion protein for incorporation into a DNL construct. Where chemical cross-linking is utilized, the AD and DDD conjugates may comprise any molecule that may be cross-linked to an AD or DDD sequence using any cross-linking technique known in the art. In certain exemplary embodiments, a dendrimer or other polymeric moiety such as polyethyleneimine or polyethylene glycol (PEG), may be incorporated into a DNL construct, as described in further detail below. 
     Expression Vectors 
     The plasmid vector pdHL2 has been used to produce a number of antibodies and antibody-based constructs. See Gillies et al., J Immunol Methods (1989), 125:191-202; Losman et al., Cancer (Phila) (1997), 80:2660-6. The di-cistronic mammalian expression vector directs the synthesis of the heavy and light chains of IgG. The vector sequences are mostly identical for many different IgG-pdHL2 constructs, with the only differences existing in the variable domain (VH and V L ) sequences. Using molecular biology tools known to those skilled in the art, these IgG expression vectors can be converted into Fab-DDD or Fab-AD expression vectors. 
     To generate Fab-DDD expression vectors, the coding sequences for the hinge, CH2 and CH3 domains of the heavy chain were replaced with a sequence encoding the first 4 residues of the hinge, a 14 residue Gly-Ser linker and a DDD moiety, such as the first 44 residues of human RIIa (referred to as DDD1, SEQ ID NO:25). To generate Fab-AD expression vectors, the sequences for the hinge, CH2 and CH3 domains of IgG were replaced with a sequence encoding the first 4 residues of the hinge, a 15 residue Gly-Ser linker and an AD moiety, such as a 17 residue synthetic AD called AKAP-IS (referred to as AD1, SEQ ID NO:27), which was generated using bioinformatics and peptide array technology and shown to bind RIIα dimers with a very high affinity (0.4 nM). See Alto, et al. Proc. Natl. Acad. Sci., U.S.A (2003), 100:4445-50. 
     Two shuttle vectors were designed to facilitate the conversion of IgG-pdHL2 vectors to either Fab-DDD1 or Fab-AD1 expression vectors, as described below. 
     Preparation of CH1 
     The CH1 domain was amplified by PCR using the pdHL2 plasmid vector as a template. The left PCR primer consisted of the upstream (5′) end of the CH1 domain and a SacII restriction endonuclease site, which is 5′ of the CH1 coding sequence. The right primer consisted of the sequence coding for the first 4 residues of the hinge followed by four glycines and a serine, with the final two codons (GS) comprising a Bam HI restriction site. The 410 bp PCR amplimer was cloned into the PGEMT® PCR cloning vector (PROMEGA®, Inc.) and clones were screened for inserts in the T7 (5′) orientation. 
     A duplex oligonucleotide was synthesized to code for the amino acid sequence of DDD1 preceded by 11 residues of the linker peptide, with the first two codons comprising a BamHI restriction site. A stop codon and an EagI restriction site are appended to the 3′ end. The encoded polypeptide sequence is shown below. 
     
       
         
           
               
            
               
                 (SEQ ID NO: 148) 
               
               
                 GSGGGGSGGGG SHIQIPPGLTELLQGYTVEVLRQQPPDLVEFAVEYFTRL   
               
               
                 
                   REARA 
                 
               
            
           
         
       
     
     Two oligonucleotides, designated RIIA1-44 top and RIIA1-44 bottom, which overlap by 30 base pairs on their 3′ ends, were synthesized and combined to comprise the central 154 base pairs of the 174 bp DDD1 sequence. The oligonucleotides were annealed and subjected to a primer extension reaction with Taq polymerase. Following primer extension, the duplex was amplified by PCR. The amplimer was cloned into PGEMT® and screened for inserts in the T7 (5′) orientation. 
     A duplex oligonucleotide was synthesized to code for the amino acid sequence of AD1 preceded by 11 residues of the linker peptide with the first two codons comprising a BamHI restriction site. A stop codon and an EagI restriction site are appended to the 3′ end. The encoded polypeptide sequence is shown below. 
     
       
         
           
               
               
            
               
                   
                 (SEQ ID NO: 149) 
               
               
                   
                 GSGGGGSGGGGS QIEYLAKQIVDNAIQQA   
               
            
           
         
       
     
     Two complimentary overlapping oligonucleotides encoding the above peptide sequence, designated AKAP-IS Top and AKAP-IS Bottom, were synthesized and annealed. The duplex was amplified by PCR. The amplimer was cloned into the PGEMT® vector and screened for inserts in the T7 (5′) orientation. 
     Ligating DDD1 with CH1 
     A 190 bp fragment encoding the DDD1 sequence was excised from PGEMT® with BamHI and NotI restriction enzymes and then ligated into the same sites in CH1-PGEMT® to generate the shuttle vector CH1-DDD1-PGEMT®. 
     Ligating AD1 with CH1 
     A 110 bp fragment containing the AD1 sequence was excised from PGEMT® with BamHI and NotI and then ligated into the same sites in CH1-PGEMT® to generate the shuttle vector CH1-AD1-PGEMT®. 
     Cloning CH1-DDD1 or CH1-AD1 into pdHL2-Based Vectors 
     With this modular design either CH1-DDD1 or CH1-AD1 can be incorporated into any IgG construct in the pdHL2 vector. The entire heavy chain constant domain is replaced with one of the above constructs by removing the SacII/EagI restriction fragment (CH1-CH3) from pdHL2 and replacing it with the SacII/EagI fragment of CH1-DDD1 or CH1-AD1, which is excised from the respective PGEMT® shuttle vector. 
     Construction of h679-Fd-AD1-pdHL2 
     h679-Fd-AD1-pdHL2 is an expression vector for production of h679 Fab with AD1 coupled to the carboxyl terminal end of the CH1 domain of the Fd via a flexible Gly/Ser peptide spacer composed of 14 amino acid residues. A pdHL2-based vector containing the variable domains of h679 was converted to h679-Fd-AD1-pdHL2 by replacement of the SacII/EagI fragment with the CH1-AD1 fragment, which was excised from the CH1-AD1-SV3 shuttle vector with SacII and EagI. 
     Production and Purification of h679-Fab-AD1 
     The h679-Fd-AD1-pdHL2 vector was linearized by digestion with Sal I restriction endonuclease and transfected into Sp/EEE myeloma cells (U.S. Pat. No. 7,785,880) by electroporation. The di-cistronic expression vector directs the synthesis and secretion of both h679 kappa light chain and h679 Fd-AD1, which combine to form h679 Fab-AD1. Following electroporation, the cells were plated in 96-well tissue culture plates and transfectant clones were selected with 0.05 μM methotrexate (MTX). Clones were screened for protein expression by ELISA using microtiter plates coated with a BSA-IMP260 (HSG) conjugate and detection with HRP-conjugated goat anti-human Fab. BIACORE® analysis using an HSG (IMP239) sensorchip was used to determine the productivity by measuring the initial slope obtained from injection of diluted media samples. The highest producing clone had an initial productivity of approximately 30 mg/L. A total of 230 mg of h679-Fab-AD1 was purified from 4.5 liters of roller bottle culture by single-step IMP291 affinity chromatography. Culture media was concentrated approximately 10-fold by ultrafiltration before loading onto an IMP291-affigel column. The column was washed to baseline with PBS and h679-Fab-AD1 was eluted with 1 M imidazole, 1 mM EDTA, 0.1 M NaAc, pH 4.5. SE-HPLC analysis of the eluate shows a single sharp peak with a retention time consistent with a 50 kDa protein (not shown). Only two bands, which represent the polypeptide constituents of h679-AD1, were evident by reducing SDS-PAGE analysis (not shown). 
     Construction of C-DDD1-Fd-hMN-14-pdHL2 
     C-DDD1-Fd-hMN-14-pdHL2 is an expression vector for production of a stable dimer that comprises two copies of a fusion protein C-DDD1-Fab-hMN-14, in which DDD1 is linked to hMN-14 Fab at the carboxyl terminus of CH1 via a flexible peptide spacer. The plasmid vector hMN-14(I)-pdHL2, which has been used to produce hMN-14 IgG, was converted to C-DDD1-Fd-hMN-14-pdHL2 by digestion with SacII and EagI restriction endonucleases to remove the CH1-CH3 domains and insertion of the CH1-DDD1 fragment, which was excised from the CH1-DDD1-SV3 shuttle vector with SacII and EagI. 
     The same technique has been utilized to produce plasmids for Fab expression of a wide variety of known antibodies, such as hLL1, hLL2, hPAM4, hRl, hRS7, hMN-14, hMN-15, hA19, hA20 and many others. Generally, the antibody variable region coding sequences were present in a pdHL2 expression vector and the expression vector was converted for production of an AD- or DDD-fusion protein as described above. The AD- and DDD-fusion proteins comprising a Fab fragment of any of such antibodies may be combined, in an approximate ratio of two DDD-fusion proteins per one AD-fusion protein, to generate a trimeric DNL construct comprising two Fab fragments of a first antibody and one Fab fragment of a second antibody. 
     Production and Purification of C-DDD1-Fab-hMN-14 
     The C-DDD1-Fd-hMN-14-pdHL2 vector was transfected into Sp2/0-derived myeloma cells by electroporation. C-DDD1-Fd-hMN-14-pdHL2 is a di-cistronic expression vector, which directs the synthesis and secretion of both hMN-14 kappa light chain and hMN-14 Fd-DDD1, which combine to form C-DDD1-hMN-14 Fab. The fusion protein forms a stable homodimer via the interaction of the DDD1 domain. 
     Following electroporation, the cells were plated in 96-well tissue culture plates and transfectant clones were selected with 0.05 μM methotrexate (MTX). Clones were screened for protein expression by ELISA using microtiter plates coated with WI2 (a rat anti-id monoclonal antibody to hMN-14) and detection with HRP-conjugated goat anti-human Fab. The initial productivity of the highest producing C-DDD1-Fab-hMN14 Fab clone was 60 mg/L. 
     Affinity Purification of C-DDD1-hMN-14 with AD1-Affigel 
     The DDD/AD interaction was utilized to affinity purify DDD1-containing constructs. AD1-C is a peptide that was made synthetically consisting of the AD1 sequence and a carboxyl terminal cysteine residue, which was used to couple the peptide to Affigel following reaction of the sulfhydryl group with chloroacetic anhydride. DDD-containing dimer structures specifically bind to the AD1-C-Affigel resin at neutral pH and can be eluted at low pH (e.g., pH 2.5). 
     A total of 81 mg of C-DDD1-Fab-hMN-14 was purified from 1.2 liters of roller bottle culture by single-step AD1-C affinity chromatography. Culture media was concentrated approximately 10-fold by ultrafiltration before loading onto an AD1-C-affigel column. The column was washed to baseline with PBS and C-DDD1-Fab-hMN-14 was eluted with 0.1 M Glycine, pH 2.5. SE-HPLC analysis of the eluate showed a single protein peak with a retention time consistent with a 107 kDa protein (not shown). The purity was also confirmed by reducing SDS-PAGE, showing only two bands of molecular size expected for the two polypeptide constituents of C-DDD1-Fab-hMN-14 (not shown). 
     The binding activity of C-DDD1-Fab-hMN-14 was determined by SE-HPLC analysis of samples in which the test article was mixed with various amounts of WI2. A sample prepared by mixing WI2 Fab and C-DDD1-Fab-hMN-14 at a molar ratio of 0.75:1 showed three peaks, which were attributed to unbound C-DDD1-Fab-hMN14 (8.71 min), C-DDD1-Fab-hMN-14 bound to one WI2 Fab (7.95 min), and C-DDD1-Fab-hMN14 bound to two WI2 Fabs (7.37 min) (not shown). When a sample containing WI2 Fab and C-DDD1-Fab-hMN-14 at a molar ratio of 4 was analyzed, only a single peak at 7.36 minutes was observed (not shown). These results demonstrated that hMN14-Fab-DDD1 is dimeric and has two active binding sites. Very similar results were obtained when this experiment was repeated with an hMN-14 Fab construct with DDD1 linked to the amino terminal instead of the carboxyl terminal end (not shown). 
     A competitive ELISA demonstrated that C-DDD1-Fab-hMN-14 binds to CEA with an avidity similar to hMN-14 IgG, and significantly stronger than monovalent hMN-14 Fab (not shown). ELISA plates were coated with a fusion protein containing the epitope (A3B3) of CEA for which hMN-14 is specific. 
     C-DDD2-Fd-hMN-14-pdHL2 
     C-DDD2-Fd-hMN-14-pdHL2 is an expression vector for production of C-DDD2-Fab-hMN-14, which possesses a dimerization and docking domain sequence of DDD2 (SEQ ID NO:26) appended to the carboxyl terminus of the Fd of hMN-14 via a 14 amino acid residue Gly/Ser peptide linker. The fusion protein secreted is composed of two identical copies of hMN-14 Fab held together by non-covalent interaction of the DDD2 domains. 
     The expression vector was engineered as follows. Two overlapping, complimentary oligonucleotides, which comprise the coding sequence for part of the linker peptide and residues 1-13 of DDD2, were made synthetically. The oligonucleotides were annealed and phosphorylated with T4 PNK, resulting in overhangs on the 5′ and 3′ ends that are compatible for ligation with DNA digested with the restriction endonucleases BamHI and PstI, respectively. 
     The duplex DNA was ligated with the shuttle vector CH1-DDD1-PGEMT®, which was prepared by digestion with BamHI and PstI, to generate the shuttle vector CH1-DDD2-PGEMT®. A 507 bp fragment was excised from CH1-DDD2-PGEMT® with SacII and EagI and ligated with the IgG expression vector hMN-14(I)-pdHL2, which was prepared by digestion with SacII and EagI. The final expression construct was designated C-DDD2-Fd-hMN-14-pdHL2. Similar techniques have been utilized to generated DDD2-fusion proteins of the Fab fragments of a number of different humanized antibodies. 
     h679-Fd-AD2-pdHL2 
     h679-Fab-AD2, was designed to pair to C-DDD2-Fab-hMN-14. h679-Fd-AD2-pdHL2 is an expression vector for the production of h679-Fab-AD2, which possesses an anchoring domain sequence of AD2 (SEQ ID NO:28) appended to the carboxyl terminal end of the CH1 domain via a 14 amino acid residue Gly/Ser peptide linker. AD2 has one cysteine residue preceding and another one following the anchor domain sequence of AD1. 
     The expression vector was engineered as follows. Two overlapping, complimentary oligonucleotides (AD2 Top and AD2 Bottom), which comprise the coding sequence for AD2 and part of the linker sequence, were made synthetically. The oligonucleotides were annealed and phosphorylated with T4 PNK, resulting in overhangs on the 5′ and 3′ ends that are compatible for ligation with DNA digested with the restriction endonucleases BamHI and SpeI, respectively. 
     The duplex DNA was ligated into the shuttle vector CH1-AD1-PGEMT®, which was prepared by digestion with BamHI and SpeI, to generate the shuttle vector CH1-AD2-PGEMT®. A 429 base pair fragment containing CH1 and AD2 coding sequences was excised from the shuttle vector with SacII and EagI restriction enzymes and ligated into h679-pdHL2 vector that prepared by digestion with those same enzymes. The final expression vector is h679-Fd-AD2-pdHL2. 
     Example 3 
     Generation of Trimeric DNL Constructs 
     TF2 DNL Construct 
     A trimeric DNL construct designated TF2 was obtained by reacting C-DDD2-Fab-hMN-14 with h679-Fab-AD2. A pilot batch of TF2 was generated with &gt;90% yield as follows. Protein L-purified C-DDD2-Fab-hMN-14 (200 mg) was mixed with h679-Fab-AD2 (60 mg) at a 1.4:1 molar ratio. The total protein concentration was 1.5 mg/ml in PBS containing 1 mM EDTA. Subsequent steps involved TCEP reduction, HIC chromatography, DMSO oxidation, and IMP 291 affinity chromatography. Before the addition of TCEP, SE-HPLC did not show any evidence of a 2 b formation. Addition of 5 mM TCEP rapidly resulted in the formation of a 2 b complex consistent with a 157 kDa protein expected for the binary structure. TF2 was purified to near homogeneity by IMP 291 affinity chromatography (not shown). IMP 291 is a synthetic peptide containing the HSG hapten to which the 679 Fab binds (Rossi et al., 2005, Clin Cancer Res 11:7122s-29s). SE-HPLC analysis of the IMP 291 unbound fraction demonstrated the removal of a 4 , a 2  and free kappa chains from the product (not shown). 
     The functionality of TF2 was determined by BIACORE® assay. TF2, C-DDD1-hMN-14+h679-AD1 (used as a control sample of noncovalent a 2 b complex), or C-DDD2-hMN-14+h679-AD2 (used as a control sample of unreduced a 2  and b components) were diluted to 1 μg/ml (total protein) and passed over a sensorchip immobilized with HSG. The response for TF2 was approximately two-fold that of the two control samples, indicating that only the h679-Fab-AD component in the control samples would bind to and remain on the sensorchip. Subsequent injections of WI2 IgG, an anti-idiotype antibody for hMN-14, demonstrated that only TF2 had a DDD-Fab-hMN-14 component that was tightly associated with h679-Fab-AD as indicated by an additional signal response. The additional increase of response units resulting from the binding of WI2 to TF2 immobilized on the sensorchip corresponded to two fully functional binding sites, each contributed by one subunit of C-DDD2-Fab-hMN-14. This was confirmed by the ability of TF2 to bind two Fab fragments of WI2 (not shown). 
     TF10 DNL Construct 
     A similar protocol was used to generate a trimeric TF10 DNL construct, comprising two copies of a C-DDD2-Fab-hPAM4 and one copy of C-AD2-Fab-679. The TF10 bispecific ([hPAM4] 2 ×h679) antibody was produced using the method disclosed for production of the (anti CEA) 2 ×anti HSG bsAb TF2, as described above. The TF10 construct bears two humanized PAM4 Fabs and one humanized 679 Fab. 
     The two fusion proteins (hPAM4-DDD2 and h679-AD2) were expressed independently in stably transfected myeloma cells. The tissue culture supernatant fluids were combined, resulting in a two-fold molar excess of hPAM4-DDD2. The reaction mixture was incubated at room temperature for 24 hours under mild reducing conditions using 1 mM reduced glutathione. Following reduction, the DNL reaction was completed by mild oxidation using 2 mM oxidized glutathione. TF10 was isolated by affinity chromatography using IMP291-affigel resin, which binds with high specificity to the h679 Fab. 
     Example 4 
     Production of AD- and DDD-linked Fab and IgG Fusion Proteins From Multiple Antibodies 
     Using the techniques described in the preceding Examples, the IgG and Fab fusion proteins shown in Table 7 were constructed and incorporated into DNL constructs. The fusion proteins retained the antigen-binding characteristics of the parent antibodies and the DNL constructs exhibited the antigen-binding activities of the incorporated antibodies or antibody fragments. 
     
       
         
           
               
             
               
                 TABLE 7 
               
             
            
               
                   
               
               
                 Fusion proteins comprising IgG or Fab 
               
            
           
           
               
               
               
            
               
                   
                 Fusion Protein 
                 Binding Specificity 
               
               
                   
                   
               
               
                   
                 C-AD1-Fab-h679 
                 HSG 
               
               
                   
                 C-AD2-Fab-h679 
                 HSG 
               
               
                   
                 C-(AD) 2 -Fab-h679 
                 HSG 
               
               
                   
                 C-AD2-Fab-h734 
                 Indium-DTPA 
               
               
                   
                 C-AD2-Fab-hA20 
                 CD20 
               
               
                   
                 C-AD2-Fab-hA20L 
                 CD20 
               
               
                   
                 C-AD2-Fab-hL243 
                 HLA-DR 
               
               
                   
                 C-AD2-Fab-hLL2 
                 CD22 
               
               
                   
                 N-AD2-Fab-hLL2 
                 CD22 
               
               
                   
                 C-AD2-IgG-hMN-14 
                 CEACAM5 
               
               
                   
                 C-AD2-IgG-hR1 
                 IGF-1R 
               
               
                   
                 C-AD2-IgG-hRS7 
                 EGP-1 
               
               
                   
                 C-AD2-IgG-hPAM4 
                 MUC 
               
               
                   
                 C-AD2-IgG-hLL1 
                 CD74 
               
               
                   
                 C-DDD1-Fab-hMN-14 
                 CEACAM5 
               
               
                   
                 C-DDD2-Fab-hMN-14 
                 CEACAM5 
               
               
                   
                 C-DDD2-Fab-h679 
                 HSG 
               
               
                   
                 C-DDD2-Fab-hA19 
                 CD19 
               
               
                   
                 C-DDD2-Fab-hA20 
                 CD20 
               
               
                   
                 C-DDD2-Fab-hAFP 
                 AFP 
               
               
                   
                 C-DDD2-Fab-hL243 
                 HLA-DR 
               
               
                   
                 C-DDD2-Fab-hLL1 
                 CD74 
               
               
                   
                 C-DDD2-Fab-hLL2 
                 CD22 
               
               
                   
                 C-DDD2-Fab-hMN-3 
                 CEACAM6 
               
               
                   
                 C-DDD2-Fab-hMN-15 
                 CEACAM6 
               
               
                   
                 C-DDD2-Fab-hPAM4 
                 MUC 
               
               
                   
                 C-DDD2-Fab-hR1 
                 IGF-1R 
               
               
                   
                 C-DDD2-Fab-hRS7 
                 EGP-1 
               
               
                   
                 N-DDD2-Fab-hMN-14 
                 CEACAM5 
               
               
                   
                   
               
            
           
         
       
     
     Example 5 
     Antibody-Dendrimer DNL Complex for siRNA 
     Cationic polymers, such as polylysine, polyethylenimine, or polyamidoamine (PAMAM)-based dendrimers, form complexes with nucleic acids. However, their potential applications as non-viral vectors for delivering therapeutic genes or siRNAs remain a challenge. One approach to improve selectivity and potency of a dendrimeric nanoparticle may be achieved by conjugation with an antibody that internalizes upon binding to target cells. 
     We synthesized and characterized a novel immunoconjugate, designated E1-G5/2, which was made by the DNL method to comprise half of a generation 5 (G5) PAMAM dendrimer (G5/2) site-specifically linked to a stabilized dimer of Fab derived from hRS7, a humanized antibody that is rapidly internalized upon binding to the Trop-2 antigen expressed on various solid cancers. 
     Methods 
     E1-G5/2 was prepared by combining two self-assembling modules, AD2-G5/2 and hRS7-Fab-DDD2, under mild redox conditions, followed by purification on a Protein L column. To make AD2-G5/2, we derivatized the AD2 peptide with a maleimide group to react with the single thiol generated from reducing a G5 PAMAM with a cystamine core and used reversed-phase HPLC to isolate AD2-G5/2. We produced hRS7-Fab-DDD2 as a fusion protein in myeloma cells, as described in the Examples above. 
     The molecular size, purity and composition of E1-G5/2 were analyzed by size-exclusion HPLC, SDS-PAGE, and Western blotting. The biological functions of E1-G5/2 were assessed by binding to an anti-idiotype antibody against hRS7, a gel retardation assay, and a DNase protection assay. 
     Results 
     E1-G5/2 was shown by size-exclusion HPLC to consist of a major peak (&gt;90%) flanked by several minor peaks (not shown). The three constituents of E1-G5/2 (Fd-DDD2, the light chain, and AD2-G5/2) were detected by reducing SDS-PAGE and confirmed by Western blotting (not shown). Anti-idiotype binding analysis revealed E1-G5/2 contained a population of antibody-dendrimer conjugates of different size, all of which were capable of recognizing the anti-idiotype antibody, thus suggesting structural variability in the size of the purchased G5 dendrimer (not shown). Gel retardation assays showed E1-G5/2 was able to maximally condense plasmid DNA at a charge ratio of 6:1 (+/−), with the resulting dendriplexes completely protecting the complexed DNA from degradation by DNase I (not shown). 
     Conclusion 
     The DNL technique can be used to build dendrimer-based nanoparticles that are targetable with antibodies. Such agents have improved properties as carriers of drugs, plasmids or siRNAs for applications in vitro and in vivo. In preferred embodiments, anti-B-cell antibodies, such as anti-CD74 and/or anti-CD20, may be utilized to deliver cytotoxic or cytostatic siRNA species to targeted B-cells for therapy of lymphoma, leukemia, autoimmune or other diseases and conditions. 
     Example 6 
     Targeted Delivery of siRNA Using Protamine Linked Antibodies 
     Summary 
     RNA interference (RNAi) has been shown to down-regulate the expression of various proteins such as HER2, VEGF, Raf-1, bcl-2, EGFR and numerous others in preclinical studies. Despite the potential of RNAi to silence specific genes, the full therapeutic potential of RNAi remains to be realized due to the lack of an effective delivery system to target cells in vivo. 
     To address this critical need, we developed novel DNL constructs having multiple copies of human protamine tethered to a tumor-targeting, internalizing hRS7 (anti-Trop-2) antibody for targeted delivery of siRNAs in vivo. A DDD2-L-thP1 module comprising truncated human protamine (thP1, residues 8 to 29 of human protamine 1) was produced, in which the sequences of DDD2 and thP1 were fused respectively to the N- and C-terminal ends of a humanized antibody light chain (not shown). The sequence of the truncated hP1 (thP1) is shown below. Reaction of DDD2-L-thP1 with the antibody hRS7-IgG-AD2 under mild redox conditions, as described in the Examples above, resulted in the formation of an E1-L-thP1 complex (not shown), comprising four copies of thP1 attached to the carboxyl termini of the hRS7 heavy chains. 
     
       
         
           
               
               
            
               
                   
                 tHP 1 
               
               
                   
                 (SEQ ID NO: 150) 
               
               
                   
                 RSQSRSRYYRQRQRSRRRRRRS  
               
            
           
         
       
     
     The purity and molecular integrity of E1-L-thP1 following Protein A purification were determined by size-exclusion HPLC and SDS-PAGE (not shown). In addition, the ability of E1-L-thP1 to bind plasmid DNA or siRNA was demonstrated by the gel shift assay (not shown). E1-L-thP1 was effective at binding short double-stranded oligonucleotides (not shown) and in protecting bound DNA from digestion by nucleases added to the sample or present in serum (not shown). 
     The ability of the E1-L-thP1 construct to internalize siRNAs into Trop-2-expressing cancer cells was confirmed by fluorescence microscopy using FITC-conjugated siRNA and the human Calu-3 lung cancer cell line (not shown). 
     Methods 
     The DNL technique was employed to generate E1-L-thP1. The hRS7 IgG-AD module, constructed as described in the Examples above, was expressed in myeloma cells and purified from the culture supernatant using Protein A affinity chromatography. The DDD2-L-thP1 module was expressed as a fusion protein in myeloma cells and was purified by Protein L affinity chromatography. Since the CH3-AD2-IgG module possesses two AD2 peptides and each can bind to a DDD2 dimer, with each DDD2 monomer attached to a protamine moiety, the resulting E1-L-thP1 conjugate comprises four protamine groups. E1-L-thp1 was formed in nearly quantitative yield from the constituent modules and was purified to near homogeneity (not shown) with Protein A. 
     DDD2-L-thP1 was purified using Protein L affinity chromatography and assessed by size exclusion HPLC analysis and SDS-PAGE under reducing and nonreducing conditions (data not shown). A major peak was observed at 9.6 min (not shown). SDS-PAGE showed a major band between 30 and 40 kDa in reducing gel and a major band about 60 kDa (indicating a dimeric form of DDD2-L-thP1) in nonreducing gel (not shown). The results of Western blotting confirmed the presence of monomeric DDD2-L-tPl and dimeric DDD2-L-tPl on probing with anti-DDD antibodies (not shown). 
     To prepare the E1-L-thP1, hRS7-IgG-AD2 and DDD2-L-thP1 were combined in approximately equal amounts and reduced glutathione (final concentration 1 mM) was added. Following an overnight incubation at room temperature, oxidized glutathione was added (final concentration 2 mM) and the incubation continued for another 24 h. E1-L-thP1 was purified from the reaction mixture by Protein A column chromatography and eluted with 0.1 M sodium citrate buffer (pH 3.5). The product peak (not shown) was neutralized, concentrated, dialyzed with PBS, filtered, and stored in PBS containing 5% glycerol at 2 to 8° C. The composition of E1-L-thP1 was confirmed by reducing SDS-PAGE (not shown), which showed the presence of all three constituents (AD2-appended heavy chain, DDD2-L-htP1, and light chain). 
     The ability of DDD2-L-thP1 and E1-L-thP1 to bind DNA was evaluated by gel shift assay. DDD2-L-thP1 retarded the mobility of 500 ng of a linear form of 3-kb DNA fragment in 1% agarose at a molar ratio of 6 or higher (not shown). E1-L-thP1 retarded the mobility of 250 ng of a linear 200-bp DNA duplex in 2% agarose at a molar ratio of 4 or higher (not shown), whereas no such effect was observed for hRS7-IgG-AD2 alone (not shown). The ability of E1-L-thP1 to protect bound DNA from degradation by exogenous DNase and serum nucleases was also demonstrated (not shown). 
     The ability of E1-L-thP1 to promote internalization of bound siRNA was examined in the Trop-2 expressing ME-180 cervical cell line (not shown). Internalization of the E1-L-thP1 complex was monitored using FITC conjugated goat anti-human antibodies. The cells alone showed no fluorescence (not shown). Addition of FITC-labeled siRNA alone resulted in minimal internalization of the siRNA (not shown). Internalization of E1-L-thP1 alone was observed in 60 minutes at 37° C. (not shown). E1-L-thP1 was able to effectively promote internalization of bound FITC-conjugated siRNA (not shown). E1-L-thP1 (10 μg) was mixed with FITC-siRNA (300 nM) and allowed to form E1-L-thP1-siRNA complexes which were then added to Trop-2-expressing Calu-3 cells. After incubation for 4 h at 37° C. the cells were checked for internalization of siRNA by fluorescence microscopy (not shown). 
     The ability of E1-L-thP1 to induce apoptosis by internalization of siRNA was examined. E1-L-thP1 (10 μg) was mixed with varying amounts of siRNA (AllStars Cell Death siRNA, Qiagen, Valencia, Calif.). The E1-L-thP1-siRNA complex was added to ME-180 cells. After 72 h of incubation, cells were trypsinized and annexin V staining was performed to evaluate apoptosis. The Cell Death siRNA alone or E1-L-thP1 alone had no effect on apoptosis (not shown). Addition of increasing amounts of E1-L-thP1-siRNA produced a dose-dependent increase in apoptosis (not shown). These results show that E1-L-thP1 could effectively deliver siRNA molecules into the cells and induce apoptosis of target cells. 
     Conclusions 
     The DNL technology provides a modular approach to efficiently tether multiple protamine molecules to the anti-Trop-2 hRS7 antibody resulting in the novel molecule E1-L-thP1. SDS-PAGE demonstrated the homogeneity and purity of E1-L-thP1. DNase protection and gel shift assays showed the DNA binding activity of E1-L-thP1. E1-L-thP1 internalized in the cells like the parental hRS7 antibody and was able to effectively internalize siRNA molecules into Trop-2-expressing cells, such as ME-180 and Calu-3. 
     The skilled artisan will realize that the DNL technique is not limited to any specific antibody or siRNA species. Rather, the same methods and compositions demonstrated herein can be used to make targeted delivery complexes comprising any antibody, any siRNA carrier and any siRNA species. The use of a bivalent IgG in targeted delivery complexes would result in prolonged circulating half-life and higher binding avidity to target cells, resulting in increased uptake and improved efficacy. 
     Example 7 
     Ribonuclease Based DNL Immunotoxins Comprising Quadruple Ranpirnase (Rap) Conjugated to B-Cell Targeting Antibodies 
     We applied the DNL method to generate a novel class of immunotoxins, each of which comprises four copies of Rap site-specifically linked to a bivalent IgG. We combined a recombinant Rap-DDD module, produced in  E. coli , with recombinant, humanized IgG-AD modules, which were produced in myeloma cells and targeted B-cell lymphomas and leukemias via binding to CD20 (hA20, veltuzumab), CD22 (hLL2, epratuzumab) or HLA-DR (hL243, IMMU-114), to generate 20-Rap, 22-Rap and C2-Rap, respectively. For each construct, a dimer of Rap was covalently tethered to the C-terminus of each heavy chain of the respective IgG. A control construct, 14-Rap, was made similarly, using labetuzumab (hMN-14), that binds to an antigen (CEACAM5) not expressed on B-cell lymphomas/leukemias. 
     
       
         
           
               
            
               
                 Rap-DDD2 
               
               
                 (SEQ ID NO: 151) 
               
               
                 
                   pQDWLTFQKKHITNTRDVDCDNIMSTNLFHCKDKNTFIYSRPEPVKAIC 
                 
               
               
                   
               
               
                 
                   KGIIASKNVLTTSEFYLSDCNVTSRPCKYKLKKSTNKFCVTCENQAPVH 
                 
               
               
                   
               
               
                 
                   FVGVGSC 
                   GGGGSLE 
                   CGHIQIPPGLTELLQGYTVEVLRQQPPDLVEFAVE 
                 
               
               
                   
               
               
                   YFTRLREARA   VE HREIHREI 
               
            
           
         
       
     
     The deduced amino acid sequence of secreted Rap-DDD2 is shown above (SEQ ID NO:151). Rap, underlined; linker, italics; DDD2, bold;  pQ , amino-terminal glutamine converted to pyroglutamate. Rap-DDD2 was produced in  E. coli  as inclusion bodies, which were purified by IMAC under denaturing conditions, refolded and then dialyzed into PBS before purification by anion exchange chromatography. SDS-PAGE under reducing conditions resolved a protein band with a Mr appropriate for Rap-DDD2 (18.6 kDa) (not shown). The final yield of purified Rap-DDD2 was 10 mg/L of culture. 
     The DNL method was employed to rapidly generate a panel of IgG-Rap conjugates. The IgG-AD modules were expressed in myeloma cells and purified from the culture supernatant using Protein A affinity chromatography. The Rap-DDD2 module was produced and mixed with IgG-AD2 to form a DNL complex. Since the CH3-AD2-IgG modules possess two AD2 peptides and each can tether a Rap dimer, the resulting IgG-Rap DNL construct comprises four Rap groups and one IgG. IgG-Rap is formed nearly quantitatively from the constituent modules and purified to near homogeneity with Protein A. 
     Prior to the DNL reaction, the CH3-AD2-IgG exists as both a monomer, and a disulfide-linked dimer (not shown). Under non-reducing conditions, the IgG-Rap resolves as a cluster of high molecular weight bands of the expected size between those for monomeric and dimeric CH3-AD2-IgG (not shown). Reducing conditions, which reduces the conjugates to their constituent polypeptides, show the purity of the IgG-Rap and the consistency of the DNL method, as only bands representing heavy-chain-AD2 (HC-AD2), kappa light chain and Rap-DDD2 were visualized (not shown). Reversed phase HPLC analysis of 22-Rap (not shown) resolved a single protein peak at 9.10 min eluting between the two peaks of CH3-AD2-IgG-hLL2, representing the monomeric (7.55 min) and the dimeric (8.00 min) forms. The Rap-DDD2 module was isolated as a mixture of dimer and tetramer (reduced to dimer during DNL), which were eluted at 9.30 and 9.55 min, respectively (not shown). 
     LC/MS analysis of 22-Rap (not shown) showed that both the Rap-DDD2 and HC-AD2 polypeptides have an amino terminal glutamine that is converted to pyroglutamate (pQ) and that 22-Rap has 6 of its 8 constituent polypeptides modified by pQ. 
     In vitro cytotoxicity was evaluated in three NHL cell lines. Each cell line expresses CD20 at a considerably higher surface density compared to CD22; however, the internalization rate for hLL2 (anti-CD22) is much faster than hA20 (anti-CD20). 14-Rap shares the same structure as 22-Rap and 20-Rap, but its antigen (CEACAM5) is not expressed by the NHL cells. Cells were treated continuously with IgG-Rap as single agents or with combinations of the parental MAbs plus rRap. Both 20-Rap and 22-Rap killed each cell line at concentrations above 1 nM, indicating that their action is cytotoxic as opposed to merely cytostatic (not shown). 20-Rap was the most potent IgG-Rap, suggesting that antigen density may be more important than internalization rate. Similar results were obtained for Daudi and Ramos, where 20-Rap (EC50˜0.1 nM) was 3-6-fold more potent than 22-Rap (not shown). The rituximab-resistant mantle cell lymphoma line, Jeko-1, exhibits increased CD20 but decreased CD22, compared to Daudi and Ramos. Importantly, 20-Rap exhibited very potent cytotoxicity (EC 50 ˜20 pM) in Jeko-1, which was 25-fold more potent than 22-Rap (not shown). 
     The DNL method provides a modular approach to efficiently tether multiple cytotoxins onto a targeting antibody, resulting in novel immunotoxins that are expected to show higher in vivo potency due to improved pharmacokinetics and targeting specificity. Targeting Rap with a MAb to a cell surface antigen enhanced its tumor-specific cytotoxicity. Antigen density and internalization rate are both critical factors for the observed in vitro potency of IgG-Rap. In vitro results show that CD20-, CD22-, or HLA-DR-targeted IgG-Rap have potent biologic activity for therapy of B-cell lymphomas and leukemias. The skilled artisan will realize that the modular DNL technique may be utilized to produce Rap DNL constructs targeted to CD74. 
     Example 8 
     Production and Use of a DNL Construct Comprising Two Different Antibody Moieties and a Cytokine 
     In certain embodiments, trimeric DNL constructs may comprise three different effector moieties, for example two different antibody moieties and a cytokine moiety. We report here the generation and characterization of the first bispecific MAb-IFNα, designated 20-C2-2b, which comprises two copies of IFN-α2b and a stabilized F(ab) 2  of hL243 (humanized anti-HLA-DR; IMMU-114) site-specifically linked to veltuzumab (humanized anti-CD20). In vitro, 20-C2-2b inhibited each of four lymphoma and eight myeloma cell lines, and was more effective than monospecific CD20-targeted MAb-IFNα or a mixture comprising the parental antibodies and IFNα in all but one (HLA-DR − /CD20 − ) myeloma line (not shown), suggesting that 20-C2-2b should be useful in the treatment of various hematopoietic disorders. The 20-C2-2b displayed greater cytotoxicity against KMS12-BM (CD20 + /HLA-DR +  myeloma) than monospecific MAb-IFNα that targets only HLA-DR or CD20 (not shown), indicating that all three components in 20-C2-2b can contribute to toxicity. Our findings indicate that a given cell&#39;s responsiveness to MAb-IFNα depends on its sensitivity to IFNα and the specific antibodies, as well as the expression and density of the targeted antigens. 
     Because 20-C2-2b has antibody-dependent cellular cytotoxicity (ADCC), but not CDC, and can target both CD20 and HLA-DR, it is useful for therapy of a broad range of hematopoietic disorders that express either or both antigens. 
     Antibodies 
     The abbreviations used in the following discussion are: 20 (C H 3-AD2-IgG-v-mab, anti-CD20 IgG DNL module); C2 (C H 1-DDD2-Fab-hL243, anti-HLA-DR Fab 2  DNL module); 2b (dimeric IFNα2B-DDD2 DNL module); 734 (anti-in-DTPA IgG DNL module used as non-targeting control). The following MAbs were provided by Immunomedics, Inc.: veltuzumab or v-mab (anti-CD20 IgG 1 ), hL243γ4p (Immu-114, anti-HLA-DR IgG 4 ), a murine anti-IFNα MAb, and rat anti-idiotype MAbs to v-mab (WR2) and hL243 (WT). 
     DNL Constructs 
     Monospecific MAb-IFNα (20-2b-2b, 734-2b-2b and C2-2b-2b) and the bispecific HexAb (20-C2-C2) were generated by combination of an IgG-AD2-module with DDD2-modules using the DNL method, as described in the preceding Examples. The 734-2b-2b, which comprises tetrameric IFNα2b and MAb h734 [anti-Indium-DTPA IgG 1 ] was used as a non-targeting control MAb-IFNα. 
     The construction of the mammalian expression vector as well as the subsequent generation of the production clones and the purification of C H 3-AD2-IgG-v-mab are disclosed in the preceding Examples. The expressed recombinant fusion protein has the AD2 peptide linked to the carboxyl terminus of the C H 3 domain of v-mab via a 15 amino acid long flexible linker peptide. Co-expression of the heavy chain-AD2 and light chain polypeptides results in the formation of an IgG structure equipped with two AD2 peptides. The expression vector was transfected into Sp/ESF cells (an engineered cell line of Sp2/0) by electroporation. The pdHL2 vector contains the gene for dihydrofolate reductase, thus allowing clonal selection, as well as gene amplification with methotrexate (MTX). Stable clones were isolated from 96-well plates selected with media containing 0.2 μM MTX. Clones were screened for C H 3-AD2-IgG-vmab productivity via a sandwich ELISA. The module was produced in roller bottle culture with serum-free media. 
     The DDD-module, IFNα2b-DDD2, was generated as discussed above by recombinant fusion of the DDD2 peptide to the carboxyl terminus of human IFNα2b via an 18 amino acid long flexible linker peptide. As is the case for all DDD-modules, the expressed fusion protein spontaneously forms a stable homodimer. 
     The C H 1-DDD2-Fab-hL243 expression vector was generated from hL243-IgG-pdHL2 vector by excising the sequence for the C H 1-Hinge-C H 2-C H 3 domains with SacII and EagI restriction enzymes and replacing it with a 507 bp sequence encoding C H 1-DDD2, which was excised from the C-DDD2-hMN-14-pdHL2 expression vector with the same enzymes. Following transfection of C H 1-DDD2-Fab-hL243-pdHL2 into Sp/ESF cells by electroporation, stable, MTX-resistant clones were screened for productivity via a sandwich ELISA using 96-well microtiter plates coated with mouse anti-human kappa chain to capture the fusion protein, which was detected with horseradish peroxidase-conjugated goat anti-human Fab. The module was produced in roller bottle culture. 
     Roller bottle cultures in serum-free H-SFM media and fed-batch bioreactor production resulted in yields comparable to other IgG-AD2 modules and cytokine-DDD2 modules generated to date. C H 3-AD2-IgG-v-mab and IFNα2b-DDD2 were purified from the culture broths by affinity chromatography using MABSELECT™ (GE Healthcare) and HIS-SELECT® HF Nickel Affinity Gel (Sigma), respectively, as described previously (Rossi et al., Blood 2009, 114:3864-71). The culture broth containing the C H 1-DDD2-Fab-hL243 module was applied directly to KAPPASELECT® affinity gel (GE-Healthcare), which was washed to baseline with PBS and eluted with 0.1 M Glycine, pH 2.5. 
     The purity of the DNL modules was assessed by SDS-PAGE and SE-HPLC (not shown). Analysis under non-reducing conditions showed that, prior to the DNL reaction, IFNα2b-DDD2 and C H 1-DDD2-Fab-hL243 exist as disulfide-linked dimers (not shown). This phenomenon, which is always seen with DDD-modules, is beneficial, as it protects the reactive sulfhydryl groups from irreversible oxidation. In comparison, C H 3-AD2-IgG-v-mab (not shown) exists as both a monomer and a disulfide-linked dimer, and is reduced to monomer during the DNL reaction. Reducing SDS-PAGE demonstrated that each module was purified to near homogeneity and identified the component polypeptides comprising each module (not shown). 
     Generation of 20-C2-2b by DNL 
     Three DNL modules (C H 3-AD2-IgG-v-mab, C H 1-DDD2-Fab-hL243, and IFN-α2b-DDD2) were combined in equimolar quantities to generate the bsMAb-IFNα, 20-C2-2b. Following an overnight docking step under mild reducing conditions (1 mM reduced glutathione) at room temperature, oxidized glutathione was added (2 mM) to facilitate disulfide bond formation (locking). The 20-C2-2b was purified to near homogeneity using three sequential affinity chromatography steps, first with Protein A (MABSELECT™), second by IMAC using HIS-SELECT® HF Nickel Affinity Gel, and third by an hL243-anti-idiotype affinity chromatography. Only those DNL constructs comprising each of the 3 desired monomers bound to all three columns. 
     The skilled artisan will realize that affinity chromatography may be used to purify DNL complexes comprising any combination of effector moieties, so long as ligands for each of the three effector moieties can be obtained and attached to the column material. The selected DNL construct is the one that binds to each of three columns containing the ligand for each of the three effector moieties and can be eluted after washing to remove unbound complexes. 
     Generation and Characterization of 20-C2-2b 
     The bispecific MAb-IFNα was generated by combining the IgG-AD2 module, C H 3-AD2-IgG-v-mab, with two different dimeric DDD-modules, C H 1-DDD2-Fab-hL243 and IFNα2b-DDD2. Due to the random association of either DDD-module with the two AD2 groups, two side-products, 20-C2-C2 and 20-2b-2b are expected to form, in addition to 20-C2-2b. 
     Non-reducing SDS-PAGE (not shown) resolved 20-C2-2b (˜305 kDa) as a cluster of bands positioned between those of 20-C2-C2 (˜365 kDa) and 20-2b-2b (255 kDa). Reducing SDS-PAGE resolved the five polypeptides (v-mab HC-AD2, hL243 Fd-DDD2, IFNα2b-DDD2 and co-migrating v-mab and hL243 kappa light chains) comprising 20-C2-2b (not shown). IFNα2b-DDD2 and hL243 Fd-DDD2 are absent in 20-C2-C2 and 20-2b-2b. MABSELECT™ binds to all three of the major species produced in the DNL reaction, but removes any excess IFNα2b-DDD2 and C H 1-DDD2-Fab-hL243. The HIS-SELECT® unbound fraction contained mostly 20-C2-C2 (not shown). The unbound fraction from WT affinity chromatography comprised 20-2b-2b (not shown). Each of the samples was subjected to SE-HPLC and immunoreactivity analyses, which corroborated the results and conclusions of the SDS-PAGE analysis. 
     SE-HPLC analysis of 20-C2-2b resolved a predominant protein peak with a retention time (6.7 min) consistent with its calculated mass and between those of the larger 20-C2-C2 (6.6 min) and smaller 20-2b-2b (6.85 min), as well as some higher molecular weight peaks that likely represent non-covalent dimers formed via self-association of IFNα2b (not shown). 
     Immunoreactivity assays demonstrated the homogeneity of 20-C2-2b with each molecule containing the three functional groups (not shown). Incubation of 20-C2-2b with an excess of antibodies to any of the three constituent modules resulted in quantitative formation of high molecular weight immune complexes and the disappearance of the 20-C2-2b peak (not shown). The MAb-IFNα showed similar binding avidity to their parental MAbs (not shown). 
     IFNα Biological Activity 
     The specific activities for various MAb-IFNα were measured using a cell-based reporter gene assay and compared to peginterferon alfa-2b (not shown). Expectedly, the specific activity of 20-C2-2b (2454 IU/pmol), which has two IFNα2b groups, was significantly lower than those of 20-2b-2b (4447 IU/pmol) or 734-2b-2b (3764 IU/pmol), yet greater than peginterferon alfa-2b (P&lt;0.001) (not shown). The difference between 20-2b-2b and 734-2b-2b was not significant. The specific activity among all agents varies minimally when normalized to IU/pmol of total IFNα. Based on these data, the specific activity of each IFNα2b group of the MAb-IFNα is approximately 30% of recombinant IFNα2b (4000 IU/pmol). 
     In the ex-vivo setting, the 20-C2-2b DNL construct depleted lymphoma cells more effectively than normal B cells and had no effect on T cells (not shown). However, it did efficiently eliminate monocytes (not shown). Where v-mab had no effect on monocytes, depletion was observed following treatment with hL243α4p and MAb-IFNα, with 20-2b-2b and 734-2b-2b exhibiting similar toxicity (not shown). Therefore, the predictably higher potency of 20-C2-2b is attributed to the combined actions of anti-HLA-DR and IFNα, which may be augmented by HLA-DR targeting. 
     The skilled artisan will realize that the approach described here to produce and use bispecific immunocytokine, or other DNL constructs comprising three different effector moieties, may be utilized with any combinations of antibodies, antibody fragments, cytokines or other effectors that may be incorporated into a DNL construct, for example the combination of anti-CD20 and anti-CD22 with IFNα2b. 
     Example 9 
     Hexavalent DNL Constructs 
     The DNL technology described above for formation of trivalent DNL complexes was applied to generate hexavalent IgG-based DNL structures (HIDS). Because of the increased number of binding sites for target antigens, hexavalent constructs are expected to show greater affinity and/or efficacy against target cells. Two types of modules, which were produced as recombinant fusion proteins, were combined to generate a variety of HIDS. Fab-DDD2 modules were as described above. The Fab-DDD2 modules form stable homodimers that bind to AD2-containing modules. To generate HIDS, C-H-AD2-IgG modules were created to pair with the Fab-DDD2 modules. 
     C-H-AD2-IgG modules have an AD2 peptide fused to the carboxyl terminus (C) of the heavy (H) chain of IgG via a peptide linker. The DNA coding sequences for the linker peptide followed by the AD2 peptide are coupled to the 3′ end of the CH3 (heavy chain constant domain 3) coding sequence by standard recombinant DNA methodologies, resulting in a contiguous open reading frame. When the heavy chain-AD2 polypeptide is co-expressed with a light chain polypeptide, an IgG molecule is formed possessing two AD2 peptides, which can therefore bind two Fab-DDD2 dimers. The C-H-AD2-IgG module can be combined with any Fab-DDD2 module to generate a wide variety of hexavalent structures composed of an Fc fragment and six Fab fragments. If the C-H-AD2-IgG module and the Fab-DDD2 module are derived from the same parental monoclonal antibody (MAb) the resulting HIDS is monospecific with 6 binding arms to the same antigen. If the modules are instead derived from two different MAbs then the resulting HIDS are bispecific, with two binding arms for the specificity of the C-H-AD2-IgG module and 4 binding arms for the specificity of the Fab-DDD2 module. 
     The same technique has been utilized to produce DNL complexes comprising an IgG moiety attached to four effector moieties, such as cytokines. In an exemplary embodiment, an IgG moiety was attached to four copies of interferon-α2b. The antibody-cytokine DNL construct exhibited superior pharmacokinetic properties and/or efficacy compared to PEGylated forms of interferon-α2b. 
     Creation of C-H-AD2-IgG-pdHL2 Expression Vectors 
     The pdHL2 mammalian expression vector has been used to mediate the expression of many recombinant IgGs. A plasmid shuttle vector was produced to facilitate the conversion of any IgG-pdHL2 vector into a C-H-AD2-IgG-pdHL2 vector. The gene for the Fc (CH2 and CH3 domains) was amplified using the pdHL2 vector as a template and a pair of primers. The amplimer was cloned in the PGEMT® PCR cloning vector. The Fc insert fragment was excised from PGEMT® with XbaI and BamHI restriction enzymes and ligated with AD2-pdHL2 vector that was prepared by digestion of h679-Fab-AD2-pdHL2 with XbaI and BamHI, to generate the shuttle vector Fc-AD2-pdHL2. 
     To convert any IgG-pdHL2 expression vector to a C-H-AD2-IgG-pdHL2 expression vector, an 861 bp BsrGI/NdeI restriction fragment is excised from the former and replaced with a 952 bp BsrGI/NdeI restriction fragment excised from the Fc-AD2-pdHL2 vector. BsrGI cuts in the CH3 domain and NdeI cuts downstream (3′) of the expression cassette. 
     Production of C-H-AD2-hLL2 IgG 
     Epratuzumab, or hLL2 IgG, is a humanized anti-human CD22 MAb. An expression vector for C-H-AD2-hLL2 IgG was generated from hLL2 IgG-pdHL2, as described above, and used to transfect Sp2/0 myeloma cells by electroporation. Following transfection, the cells were plated in 96-well plates and transgenic clones were selected in media containing methotrexate. Clones were screened for C-H-AD2-hLL2 IgG productivity by a sandwich ELISA using 96-well microtiter plates coated with an hLL2-specific anti-idiotype MAb and detection with peroxidase-conjugated anti-human IgG. Clones were expanded to roller bottles for protein production and C-H-AD2-hLL2 IgG was purified from the spent culture media in a single step using Protein-A affinity chromatography. SDS-PAGE analysis demonstrated that the purified C-H-AD2-hLL2-IgG consisted of both monomeric and disulfide-linked dimeric forms of the module (not shown). Protein bands representing these two forms are evident by SDS-PAGE under non-reducing conditions, while under reducing conditions all of the forms are reduced to two bands representing the constituent polypeptides (Heavy chain-AD2 and kappa chain) (not shown). No other contaminating bands were detected. 
     Production of C-H-AD2-hA20 IgG 
     hA20 IgG is a humanized anti-human CD20 MAb. An expression vector for C-H-AD2-hA20 IgG was generated from hA20 IgG-pDHL2, as described above, and used to transfect Sp2/0 myeloma cells by electroporation. Following transfection, the cells were plated in 96-well plates and transgenic clones were selected in media containing methotrexate. Clones were screened for C-H-AD2-hA20 IgG productivity by a sandwich ELISA using 96-well microtiter plates coated with a hA20-specific anti-idiotype MAb and detection with peroxidase-conjugated anti-human IgG. Clones were expanded to roller bottles for protein production and C-H-AD2-hA20 IgG was purified from the spent culture media in a single step using Protein-A affinity chromatography. SE-HPLC and SDS-PAGE analyses gave very similar results to those obtained for C-H-AD2-hLL2 IgG (not shown). 
     Example 10 
     Generation of Hexavalent DNL Constructs 
     Generation of Hex-hA20 
     The DNL method was used to create Hex-hA20, a monospecific anti-CD20 HIDS, by combining C-H-AD2-hA20 IgG with hA20-Fab-DDD2. The Hex-hA20 structure contains six anti-CD20 Fab fragments and an Fc fragment, arranged as four Fab fragments and one IgG antibody. Hex-hA20 was made as described below. 
     A 210% molar equivalent of (hA20-Fab-DDD2) 2  was mixed with C-H-AD2-hA20 IgG. This molar ratio was used because two Fab-DDD2 dimers are coupled to each C-H-AD2-hA20 IgG molecule and an additional 10% excess of the former to ensure that the coupling reaction is complete. The mixture was typically made in phosphate buffered saline, pH 7.4 (PBS) with 1 mM EDTA. Then reduced glutathione (GSH) was added to a final concentration of 1 mM and the solution was held at room temperature (16-25° C.) for 1-24 hours. Following reduction, oxidized glutathione (GSSH) was added directly to the reaction mixture to a final concentration of 2 mM and the solution was held at room temperature for 1-24 hours. 
     After oxidation, the reaction mixture was loaded directly onto a Protein-A affinity chromatography column. The column was washed with PBS and the Hex-hA20 was eluted with 0.1 M glycine, pH 2.5. Since excess hA20-Fab-DDD2 was used in the reaction, there was no unconjugated C-H-AD2-hA20 IgG, or incomplete DNL structures containing only one (hA20-Fab-DDD2) 2  moiety. The unconjugated excess hA20-Fab-DDD2 does not bind to the affinity resin. The calculated molecular weight from the deduced amino acid sequences of the constituent polypeptides is 386 kDa. Size exclusion HPLC analysis showed a single protein peak with a retention time consistent with a protein structure of 375-400 kDa (not shown). 
     Generation of Hex-hLL2 
     The DNL method was used to create a monospecific anti-CD22 HIDS (Hex-hLL2) by combining C-H-AD2-hLL2 IgG with hLL2-Fab-DDD2. The DNL reaction was accomplished as described above for Hex-hA20. The calculated molecular weight from the deduced amino acid sequences of the constituent polypeptides is 386 kDa. Size exclusion HPLC analysis showed a single protein peak with a retention time consistent with a protein structure of 375-400 kDa (not shown). SDS-PAGE analysis under non-reducing conditions showed a cluster of high molecular weight bands, which were eliminated under reducing conditions to leave only the three expected polypeptide chains: HC-AD2, Fd-DDD2, and the kappa chain (not shown). 
     Generation of DNL1 and DNL1C 
     The DNL method was used to create bispecific HIDS by combining C-H-AD2-hLL2 IgG with either hA20-Fab-DDD2 to obtain DNL1 or hMN-14-DDD2 to obtain DNL1C. DNL1 has four binding arms for CD20 and two for CD22. As hMN-14 is a humanized MAb to carcinoembryonic antigen (CEACAM5), DNL1C has four binding arms for CEACAM5 and two for CD22. The DNL reactions were accomplished as described for Hex-hA20 above. HPLC and SDS-PAGE were consistent with the desired products. 
     Generation of DNL2 and DNL2C 
     The DNL method was used to create bispecific HIDS by combining C-H-AD2-hA20 IgG with either hLL2-Fab-DDD2 to obtain DNL2 or hMN-14-DDD2 to obtain DNL2C. DNL2 has four binding arms for CD22 and two for CD20. DNL2C has four binding arms for CEACAM5 and two for CD20. The DNL reactions were accomplished as described for Hex-hA20. HPLC and SDS-PAGE were consistent with the desired products. 
     Stability in Serum 
     The stability of DNL1 and DNL2 in human serum was determined using a bispecific ELISA assay. The protein structures were incubated at 10 μg/m1 in fresh pooled human sera at 37° C. and 5% CO 2  for five days. For day 0 samples, aliquots were frozen in liquid nitrogen immediately after dilution in serum. ELISA plates were coated with an anti-Id to hA20 IgG and bispecific binding was detected with an anti-Id to hLL2 IgG. Both DNL1 and DNL2 were highly stable in serum and maintained complete bispecific binding activity (not shown). 
     Binding Activity 
     The HIDS generated as described above retained the binding properties of their parental Fab/IgGs. Competitive ELISAs were used to investigate the binding avidities of the various HIDS using either a rat anti-idiotype MAb to hA20 (WR2) to assess the binding activity of the hA20 components or a rat anti-idiotype MAb to hLL2 (WN) to assess the binding activity of the hLL2 components. To assess hA20 binding, ELISA plates were coated with hA20 IgG and the HIDS were allowed to compete with the immobilized IgG for WR2 binding. To assess hLL2 binding, plates were coated with hLL2 IgG and the HIDS were allowed to compete with the immobilized IgG for WN binding. The relative amount of anti-Id bound to the immobilized IgG was detected using peroxidase-conjugated anti-Rat IgG. 
     Examining the relative CD20 binding avidities, DNL2, which has two CD20 binding groups, showed a similar binding avidity to hA20 IgG, which also has two CD20-binding arms (not shown). DNL1, which has four CD20-binding groups, had a stronger (˜4-fold) relative avidity than DNL2 or hA20 IgG (not shown). Hex-hA20, which has six CD20-binding groups, had an even stronger (˜10-fold) relative avidity than hA20 IgG (not shown). 
     Similar results were observed for CD22 binding. DNL1, which has two CD20 binding groups, showed a similar binding avidity to hLL2 IgG, which also has two CD22-binding arms (not shown). DNL2, which has four CD22-binding groups, had a stronger (&gt;5-fold) relative avidity than DNL1 or hLL2 IgG. Hex-hLL2, which has six CD22-binding groups, had an even stronger (&gt;10-fold) relative avidity than hLL2 IgG (not shown). As both DNL2 and DNL3 contain two hA20 Fabs and four hLL2 Fabs, they showed similar strength in binding to the same anti-id antibody (not shown). 
     In Vivo Anti-Tumor Activity 
     The HIDS were shown to have therapeutic efficacy in vivo using a human Burkitt Lymphoma model in mice. Low doses (12 μs) of DNL2 and Hex-hA20 more than doubled the survival times of tumor bearing mice. Treatment with higher doses (60 μg) resulted in long-term survivors. 
     In Vitro Activity 
     Some of the HIDS were observed to have potent anti-proliferative activity on lymphoma cell lines. DNL1, DNL2 and Hex-hA20 inhibited cell growth of Daudi Burkitt Lymphoma cells in vitro (not shown). Treatment of the cells with 10 nM concentrations was substantially more effective for the HIDS compared to rituximab (not shown). Using a cell counting assay, the potency of DNL1 and DNL2 was estimated to be more than 100-fold greater than that of rituximab, while the Hex-hA20 was shown to be even more potent (not shown). This was confirmed with an MTS proliferation assay in which dose-response curves were generated for Daudi cells treated with a range of concentrations of the HIDS (not shown). Compared to rituximab, the bispecific HIDS (DNL1 and DNL2) and Hex-hA20 were &gt;100-fold and &gt;10000-fold more potent, respectively. 
     Dose-response curves for HIDS (DNL1, DNL2, Hex-hA20) versus a parent IgG (hA20 IgG) were compared for three different lymphoma cell lines, using an MTS proliferation assay. In Daudi lymphoma cells, the bispecific structures DNL1 and DNL2 showed &gt;100-fold more potent anti-proliferative activity and Hex-hA20 showed &gt;10,000-fold more potent activity than the parent hA20 IgG (not shown). Hex-hLL2 and the control structures (DNL1-C and DNL2-C) had very little anti-proliferative activity in this assay (not shown). 
     In Raji lymphoma cells, Hex-hA20 displayed potent anti-proliferative activity, but DNL2 showed only minimal activity compared with hA20 IgG (not shown). In Ramos lymphoma cells, both DNL2 and Hex-hA20 displayed potent anti-proliferative activity, compared with hA20 IgG (not shown). These results show that the increased potency of HIDS relative to the parent IgGs is not limited to particular cell lines, but rather is a general phenomenon for cells displaying the appropriate targets. 
     CDC and ADCC Activity of Hexavalent DNL Constructs 
     In vivo, anti-CD20 monoclonal antibodies such as rituximab and hA20 can utilize complement-dependent cytotoxicity (CDC), antibody-dependent cellular cytotoxicity (ADCC) and signal transduction induced growth inhibition/apoptosis for tumor cell killing. The hexavalent DNL structures (DNL1, DNL2, Hex-hA20) were tested for CDC activity using Daudi cells in an in vitro assay. Surprisingly, none of the hexavalent structures that bind CD20 exhibited CDC activity (not shown). The parent hA20 IgG exhibited potent CDC activity (not shown), while as expected the hLL2 antibody against CD22 showed no activity (not shown). The lack of effect of DNL2 and Hex-hA20 was of interest, since they comprise hA20-IgG-Ad2, which showed similar positive CDC activity to hA20 IgG (not shown). 
     DNL1 was assayed for ADCC activity using freshly isolated peripheral blood mononuclear cells. Both rituximab and hA20 IgG showed potent activity on Daudi cells, while DNL1 did not exhibit any detectable ADCC activity (not shown). 
     These data suggest that the Fc region may become inaccessible for effector functions (CDC and ADCC) when four additional Fab groups are tethered to its carboxyl termini. Therefore, the hexavalent DNL structures appear to rely only on signal transduction induced growth inhibition/apoptosis for in vivo anti-tumor activity. 
     Example 11 
     Combination DNL Constructs Comprising Anti-CD74 Antibodies Show Potent Toxicity Against B Cell Lymphoma 
     Juxtaposing CD20 and CD74 by Bispecific Antibodies Evokes Potent Cytotoxicity in Mantle Cell Lymphoma 
     Abstract 
     We describe the potent growth-inhibitory and apoptotic activities of two bispecific hexavalent antibodies (HexAbs) constructed by the dock-and-lock (DNL) technique from veltuzumab (anti-CD20) and milatuzumab (anti-CD74) in mantle cell lymphoma (MCL) and other lymphoma/leukemia lines, as well as primary patient tumor samples. In vitro, the bispecific HexAbs had different properties and were more potent than their parental antibodies. The juxtaposition of CD20 and CD74 on MCL cells by the HexAbs resulted in homotypic adhesion and triggered intracellular changes that included loss of mitochondrial membrane potential, production of reactive oxygen species, increased phosphorylation of ERKs and JNK, downregulation of pAkt and Bcl-xL, and enlargement of lysosomes, culminating in cell death. The two HexAbs also displayed different potencies in depleting lymphoma cells from whole blood ex vivo, and significantly extended the survival of nude mice bearing MCL xenografts. 
     Introduction 
     Mantle cell lymphoma (MCL) is an aggressive subtype of B-cell non-Hodgkin lymphoma (NHL) generally having a poor prognosis. Currently, there is no established standard of care and relapsed MCL remains a major clinical challenge. Thus, there is a need to develop new targeted therapeutics to treat this disease (Diefenbach &amp; O&#39;Connor, 2010 , Curr Opin Oncol.  22:419-423). 
     Monoclonal antibodies (MAbs), exemplified by rituximab, are among the treatment options for MCL (Weigert et al., 2009 , Leuk Lymphoma  50:1937-1950; Zhou et al., 2007 , Am J Hematol  83:144-149) and have shown encouraging results in MCL (Lenz et al., 2005 , J Clin Oncol  23:1984-1992; Sachanas et al., 2011 , Leuk Lymphoma  52:387-93). However, resistance to rituximab therapy remains a problem (Lim et al., 2011 , Blood  July 18, Epub ahead of print) and more effective methods of treatment for MCL are needed. 
     The combination of two different targeting MAbs to achieve improved efficacy without increased toxicity was shown in NHL patients receiving both rituximab and epratuzumab (humanized anti-CD22 IgG 1 , also referred to as hLL2) (Leonard et al., 2005 , J Clin Oncol  23:5044-5051; Strauss et al., 2006 , J Clin Oncol  24:3880-3886; Leonard et al., 2008 , Cancer  113:2714-2723). More recently, the potential advantage of targeting both CD20 and CD74 was reported in a preclinical study involving rituximab and milatuzumab (humanized anti-CD74 IgG 1 , also referred to as hLL1) which, in the presence of a crosslinking antibody, showed improved anti-tumor activity in MCL lines and primary patient samples than either parental antibody alone (Alinari et al., 2011 , Blood  117:4530-41; Alinari et al., 2008 , Blood  112:Abstract 886). In principle, combination antibody therapy can be accomplished with a bispecific antibody (bsAb) to avoid the need for administering two different antibodies sequentially, which is time-consuming, expensive, and inconvenient. 
     The potential of bsAbs as novel therapeutics for cancer and autoimmune disease is being explored with various constructs differing in design, structure, and antigen-binding properties. Depending on the built-in dual specificity, a bsAb may serve to recruit effector cells or effector molecules to target cells, or it may improve the target selectivity by concurrent ligation of two different antigens expressed on the same cell, wherein a multivalent bsAb should also enhance its functional affinity, resulting in increased retention on the bound cells and, likely, a higher potency. 
     The Dock-and-Lock (DNL) method, described above, is a platform technology that combines genetic engineering with site-specific conjugation to enable self-assembly of two modular components only with each other, resulting in a covalent structure of defined composition with retained bioactivity. We have applied DNL to generate various multivalent, multispecific structures that include mono- and bi-specific HexAbs, each comprising a pair of stabilized dimers of Fab linked to a full IgG at the carboxyl termini of the two heavy chains, thus conferring six Fab-arms and a common Fc entity. To identify these HexAbs, each is assigned a code of X-(Y)-(Y), where X and Y are specific numbers given to differentiate the antibodies, and a designated number enclosed in a parenthesis representing the antibody as a Fab. For example, 20-(74)-(74) designates the bispecific HexAb comprising a divalent anti-CD20 IgG of veltuzumab (also referred to as hA20) and a pair of stabilized dimers of Fab derived from milatuzumab. The designations of various HexAbs relevant to this study, which include 20-(74)-(74), 74-(20)-(20), 74-(74)-(74), 20-(20)-(20), 20-(22)-(22), and 22-(20)-(20), along with their modular components, are provided in Table 8. 
     
       
         
           
               
             
               
                 TABLE 8 
               
             
            
               
                   
               
               
                 Hexavalent Antibody Designations 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 CH 3 -AD2- 
                 CH 1 -DDD2- 
               
               
                 Designation 
                   
                 IgG module 
                 Fab module 
               
            
           
           
               
               
               
               
               
               
            
               
                 Current 
                 Previous 
                 Ab 
                 Ag 
                 Ab 
                 Ag 
               
               
                   
               
               
                 20-(74)-(74) 
                 N/A 
                 Veltuzumab 
                 CD20 
                 Milatuzumab 
                 CD74 
               
               
                 74-(20)-(20) 
                 N/A 
                 Milatuzumab 
                 CD74 
                 Epratuzumab 
                 CD20 
               
               
                 74-(74)-(74) 
                 N/A 
                 Milatuzumab 
                 CD74 
                 Milatuzumab 
                 CD74 
               
               
                 20-(20)-(20) 
                 20-20 
                 Veltuzumab 
                 CD20 
                 Veltuzumab 
                 CD20 
               
               
                 20-(22)-(22) 
                 20-22 
                 Veltuzumab 
                 CD20 
                 Epratuzumab 
                 CD22 
               
               
                 22-(20)-(20) 
                 22-20 
                 Epratuzumab 
                 CD22 
                 Veltuzumab 
                 CD20 
               
               
                   
               
            
           
         
       
     
     In our initial efforts to develop HexAbs from veltuzumab and epratuzumab, we found both 20-(22)-(22) and 22-(20)-(20) induced growth inhibition and apoptosis in Burkitt lymphoma lines (Daudi, Raji and Ramos) in the absence of a crosslinking antibody, which is often required for the parental antibodies to be effective in vitro (Rossi et al., 2008 , Cancer Res  68:8384-8392; Rossi et al., 2009 , Blood  113:6161-6171; Gupta et al., 2010 , Blood  116:3258-3267). Such direct cytotoxicity, however, was not observed in JeKo-1, a MCL line expressing comparable levels of CD20 and CD22 as Daudi NHL. 
     In the present Example, we describe the generation and characterization of three novel HexAbs, 20-(74)-(74), 74-(20)-(20), and 74-(74)-(74), from veltuzumab (hA20) and milatuzumab (hLL1). Surprisingly, even though mantle cell lymphoma was resistant to anti-CD20/CD22 HexAbs and to the parental anti-CD74 and anti-CD20 antibodies, the HexAbs based on the combination of anti-CD74 and anti-CD20 antibodies were highly cytotoxic in three blastoid MCL lines, JeKo-1, Granta-519 and Mino, as well as in primary tumor cells from patients with MCL or chronic lymphocytic leukemia (CLL). Selective experiments performed to investigate the intracellular events triggered by juxtaposing CD20 and CD74 revealed the prominent roles of actin reorganization and lysosomal membrane permeabilization (LMP) in the mechanisms of cell death. 
     Methods 
     Cell Lines, Antibodies, and Reagents— 
     All cell lines were purchased from ATCC (Manassas, Va.). Humanized antibodies, including veltuzumab, milatuzumab, epratuzumab, labetuzumab (anti-CEACAM5 IgG 1 , also referred to as hMN-14), and hRS7 (anti-human Trop-2 IgG 1 ), were obtained as described in Example 1. Tositumomab and rituximab were obtained commercially. Phospho-specific antibodies and other commercially available antibodies were acquired from Cell Signaling (Beverly, Mass.) or Santa Cruz Biotechnology (Santa Cruz, Calif.). Cell culture media, supplements, annexin V ALEXA FLUOR® 488 conjugate, tetramethylrhodamine ethyl ester (TMRE), LYSOTRACKER® Red DND-99, CM-H 2 DCF-DA, DAPI, ALEXA FLUOR® phalloidin, and acridine orange were bought from Invitrogen (Carlsbad, Calif.). One Solution Cell Proliferation assay (MTS) was obtained from Promega (Madison, Wis.). PHOSPHOSAFE™ buffer, latrunculin B, cytochalasin D, bafilomycin A1 and concanamycin A were procured from EMD chemicals (Gibbstown, N.J.). MAGIC RED′ Cathepsin B assay kit was purchased from ImmunoChemistry Technologies (Bloomington, Minn.). All other chemicals were purchased from Sigma (St. Louis, Mo.). 
     Cell Culture— 
     Malignant cell lines were cultured at 37° C. in 5% CO 2  in RPMI 1640 medium supplemented with 10% heat-inactivated fetal bovine serum, 2 mM L-glutamine, 200 U/ml penicillin and 100 μg/ml streptomycin. Cells from CLL and MCL patients were collected from whole blood by Ficoll-Hypaque separation and grown in RPMI media as described for the cell lines. 
     Cell Proliferation Assay— 
     Cells were seeded in 48-well plates (5×10 4  cells per well) and incubated with each test article at a final concentration of 0.006 to 100 nM for 4 days. The number of viable cells was then determined using the MTS assay per the manufacturer&#39;s protocol, plotted as percent of the untreated, and analyzed by Prism software. 
     Effector Function Assays— 
     ADCC was performed as described previously (Rossi et al., 2008 , Cancer Res  68:8384-8392), using JeKo-1 as the target cell and freshly isolated peripheral blood mononuclear cells as the effector cells. To perform CDC, cells were seeded in black 96-well plates at 5×10 4  cells in 50 μl per well and incubated with serial dilutions (concentration range 3.3×10 −8  to 2.6×10 −10  M) of test articles in the presence of human complement (1/20 final dilution, Quidel Corp., San Diego, Calif.) for 2 h at 37° C. and 5% CO 2 . Viable cells were then quantified using the MTS assay. Controls included cells treated with 0.25% Triton X-100 (100% lysis) and cells treated with complement alone (background). 
     Annexin V Binding Assay— 
     Cells in 6-well plates (2×10 5  cells per well) were treated with each test article at 10 nM for 24 to 48 h, washed, resuspended in 100 μl of annexin-binding buffer (10 mM HEPES, 140 mM NaCl and 2.5 mM CaCl 2  in PBS), stained with 5 μl of Annexin V-ALEXA FLUOR® 488 conjugate for 20 min, then with 1 μg/ml of propidium iodide (PI) in 400 μl of annexin binding buffer, and analyzed by flow cytometry (FACSCALIBUR®, Becton Dickinson, San Jose, Calif.). Cells stained positive with annexin V (including both PI-negative and PI-positive) were counted as apoptotic populations. When required, cells were pretreated with the indicated inhibitors for 2 h before adding the test article. 
     Immunoblot Analysis— 
     JeKo-1 cells (6×10 6  cells in 6 ml) were treated with each test article at 10 nM for a predetermined time. Cells were washed with PBS, centrifuged, and lysed in ice-cold PHOSPHOSAFE™ buffer followed by centrifugation at 13,000×g. Supernatants were collected and protein samples (20 μg) were separated by SDS-PAGE on 4-20% gradient Tris-glycine gels followed by transfer onto nitrocellulose membranes (Bio-Rad, Hercules, Calif.), which were probed with suitable antibodies and developed as described (Rossi et al., 2009 , Blood  113:6161-6171). 
     Nuclear Extracts— 
     JeKo-1 cells (6×10 6  cells in 6 ml) were treated with each test article at 10 nM for 72 h. Cells were collected and cytosolic and nuclear extracts were obtained as described (Mayo et al., 2001 , Methods Enzymol  333:73-87). Equal amounts of nuclear and cytosolic proteins (10 μg) were separated on SDS-PAGE and analyzed for NF-κB protein p65, Brg-1 and β-actin, with the latter two serving as loading controls for nuclear and cytosolic proteins, respectively. 
     Assessment of Δψ m  and ROS— 
     Flow cytometry was used to determine Δψ m  and ROS. Briefly, cells in 6-well plates (2×10 5  cells per well) were treated with each test article at 10 nM for 48 h, washed, stained for 30 min in the dark at 37° C. with TMRE (50 nM) for Ay or CM-H 2 DCF-DA (1 μM) for ROS. Samples were then washed with PBS and analyzed. 
     Assessment of Lysosomal Changes and Cathepsin B Release— 
     To determine the changes in lysosomal volumes, 2×10 5  cells per well in 6-well plates were treated with each test article at 10 nM for 48 h. After washing, cells were labeled with LYSOTRACKER® Red DND-99 (75 nM) followed by incubation in the dark at 37° C. for 1 h. Cells were washed with PBS and samples were analyzed by flow cytometry. To evaluate lysosomal membrane permeabilization, JeKo-1 cells were treated with select antibodies at 10 μg/ml for 4 h, labeled with acridine orange, and examined under a fluorescence microscope. To study cathepsin B release, JeKo-1 cells were treated with select antibodies (10 nM) for 48 h, fixed with 4% paraformaldehyde, permeabilized with 0.1% tritonX-100, costained with MAGIC RED™ Cathepsin B and DAPI, and examined under a fluorescence microscope. 
     Effect on Actin— 
     Cells were treated with various antibodies or combinations of antibodies as indicated, stained for 30 min with either rhodamine phalloidin and DAPI for actin and nucleus, respectively, or rhodamine phalloidin and FITC-conjugated, Fc fragment-specific, goat anti-human (GAH) antibody (for the location of test antibodies), and visualized under a fluorescence microscope after washing. 
     Ex Vivo Depletion of JeKo-1 and B Cells from Whole Blood— 
     JeKo-1 cells (5×10 4 ) were mixed with heparinized whole blood (150 μl) from healthy volunteers and incubated with varying concentrations of each test article for 2 d at 37° C. and 5% CO 2 . After lysing the red blood cells and washing, the remaining cells were stained with FITC-anti-CD19, PE-anti-CD14 or allophycocyanin (APC)-conjugated mouse IgG 1  isotype control, and analyzed by flow cytometry. JeKo-1 cells and monocytes were identified in the monocyte gate as CD19 +  and CD14 +  populations, respectively. Normal B cells are CD19 +  in the lymphocyte gate. 
     In Vivo Efficacy— 
     Female 8-week-old SCID mice (Taconic Farms; Germantown, N.Y.) were used. Seven different treatment groups of eight mice each were inoculated i.v. with JeKo-1 (2.5×10 7  cells). After seven days, one group received 370 μg of 20-(74)-(74) i.p. twice weekly for two weeks. A second group received 74-(20)-(20) with the same dose and schedule. Two lower doses (37 μg and 3.7 μg) also were examined for each HexAb with the same schedule and injection route. The control group received saline. The mice were observed daily for signs of distress or paralysis, weighed weekly, and killed humanely when they developed hind-limb paralysis, became moribund, or lost more than 20% of initial body weight. 
     Statistical Analyses— 
     For in vitro studies, the statistical difference between two populations was determined by Student&#39;s t-test. For in vivo studies, statistical differences in survival between treatment groups were analyzed using Kaplan-Meier plots provided by Prism software. P&lt;0.05 was considered statistically significant. 
     Results 
     Generation of HexAbs and Demonstration of Direct Cytotoxicity In Vitro— 
     The generation of monospecific and bispecific HexAbs by the DNL method from the cognate C H 3-AD2-IgG-X and C H 1-Fab-DDD2-Y, where X and Y can be either hLL1 (milatuzumab) or hA20 (veltuzumab), was performed as described in Examples 9 and 10 above. The HexAbs were purified to near homogeneity, as indicated by SDS-PAGE and SE-HPLC analyses (not shown) for 20-(74)-(74) and 74-(20)-(20). Both also showed stronger binding to three MCL cell lines (JeKo-1, Granta-519 and Mino) than their parental antibodies (data not shown). 
     In the cell proliferation assays ( FIG. 1A ), the two bispecific anti-CD20/CD74 HexAbs demonstrated potent cytotoxicity against JeKo-1, Granta-519, Mino, and Raji, with the half maximal effector concentration (EC 50 ) in the low nanomolar range. In comparison, we observed &lt;20% (Granta-519 and Raji) and &lt;50% (Jeko-1 and Mino) growth inhibition when both parental antibodies were combined at the highest concentration tested (100 nM) ( FIG. 1A ). Additional results shown in  FIG. 1B  revealed that the anti-proliferative activity of the monospecific 74-(74)-(74) and 20-(20)-(20) HexAbs, as well as the bispecific anti-CD20/CD22 HexAb, 20-(22)-(22), paralleled that of combined hLL1 and hA20 in JeKo-1, and thus was considerably lower in activity than the bispecific anti-CD20/CD74 HexAbs. 
     On the other hand, notable cytotoxicity of 20-(20)-(20) was found in Mino and Granta-519, and an initial survey showed cell lines derived from CLL (WAC and MEC-1), acute lymphocytic leukemia (REH-1 and MN60), and multiple myeloma (CAG, RPMI8266, KMS11, KMS12-BM, and KMS12-PE) were relatively resistant to the HexAbs. For both 20-(74)-(74) and 74-(20)-(20), the addition of either parental antibody at a moderate concentration of 10 μg/mL partially reduced their anti-proliferative effects in JeKo-1 ( FIG. 1C ). A list of the EC 50  values (nM), as determined by the MTS assay, is provided in Table 9. Surprisingly, DNL constructs comprising anti-CD74 and anti-CD20 antibodies or fragments thereof were substantially more effective at treating mantle cell lymphoma than anti-CD20/anti-CD22 DNL constructs or either parental antibody administered alone or together. 
     
       
         
           
               
             
               
                 TABLE 9 
               
             
            
               
                   
               
               
                 EC 50  values (nM) for HexAbs comprising hA20 and hLL1 in three MCL (JeKo-1, 
               
               
                 Granta-519, Mino) and 2 Burkitt lymphoma lines (Daudi, Raji). The EC 50  values as 
               
               
                 determined by the MTS assay for 20-(74)-(74) and 74-(20)-(20) in two CLL lines (WAC, MEC- 
               
               
                 1), 2 ALL lines (REH-1, MN60), and 5 MM lines ((CAG, RPMI8226, KMS11, KMS12-BM, 
               
               
                 KMS12-PE), were all greater than 100 nM. In MM lines, hLL1, hA20, hLL1 + GAH, 
               
               
                 hA20 + GAH, and hLL1 + hA20 + GAH show no anti-proliferative effect. 
               
            
           
           
               
               
               
            
               
                   
                 EC 50  (nM) 
                 Percent inhibition (%) at 100 nM 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                   
                 JeKo-1 
                 Granta-519 
                 Mino 
                 Daudi 
                 Raji 
                 JeKo-1 
                 Granta-519 
                 Mino 
                 Raji 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 hLL2 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 hLL1 
                   
                   
                   
                   
                   
                 0 
                 0 
                   
                   
               
               
                 hA20 
                   
                   
                   
                   
                   
                 0 
                 8 
                   
                   
               
               
                 Rituximab 
                   
                   
                   
                   
                   
                 0 
                 11 
                   
                   
               
               
                 hLL2 + 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 GAH 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 hLL1 + 
                   
                   
                   
                   
                   
                 36 
                 38 
                   
                   
               
               
                 GAH 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 hA20 + 
                   
                   
                   
                   
                   
                 27 
                 37 
                   
                   
               
               
                 GAH 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Rituximab + 
                   
                   
                   
                   
                   
                 20 
                 45 
                   
                   
               
               
                 GAH 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 hA20 + 
                 &gt;100 
                 &gt;100 
                 &gt;100 
                   
                 &gt;100 
                 0 
                 34 
                   
                   
               
               
                 hLL1 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Rituximab + 
                   
                   
                   
                   
                   
                 0 
                 40 
                   
                   
               
               
                 hLL1 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 hA20 + 
                   
                   
                   
                   
                   
                 68 
                 61 
                   
                   
               
               
                 hLL1 + 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 GAH 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Rituximab + 
                   
                   
                   
                   
                   
                 67 
                 60 
                   
                   
               
               
                 hLL1 + 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 GAH 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 20-(74)- 
                 3 
                 2 
                 13.7 
                 5.3 
                 0.3 
                 70 
                 55 
                 80 
                 50 
               
               
                 (74) 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 74-(20)- 
                 2 
                 0.6 
                 1.2 
                 1.2 
                 0.3 
                 90 
                 65 
                 100 
                 50 
               
               
                 (20) 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 74-(74)- 
                 &gt;100 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 (74) 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 20-(20)- 
                 &gt;100 
                 0.2 
                 3.4 
                 5.8 
                 8 
                   
                   
                   
                   
               
               
                 (20) 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 22-(20)- 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 (20) 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 20-(22)- 
                 &gt;100 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 (22) 
               
               
                   
               
            
           
         
       
     
     Antibody-Dependent Cellular Cytotoxicity (ADCC)— 
     HexAbs based on anti-CD20 IgG, i.e., the 20-(X)-(X) series, were expected to display ADCC with a similar potency to hA20 IgG (Rossi et al., 2008 , Cancer Res  68:8384-8392; Rossi et al., 2009 , Blood  113:6161-6171). As shown in  FIG. 6 , the mean cell lysis obtained in JeKo-1 with 20-(74)-(74) dosed at 33 nM, with a 40 to 1 effector to target cell ratio, was 30.2%, slightly higher but statistically significantly (P&lt;0.0443) more than hA20 IgG (25.5%). Under the same conditions, a much weaker ADCC (5.5% lysis) was observed for 74-(20)-(20), whereas hLL1 IgG or a non-binding control (hRS7 IgG) had no ADCC. 
     Complement-Dependent Cytotoxicity (CDC)— 
     The results of CDC were determined for JeKo-1, Granta-519, and Daudi cells. In all three cell lines, 74-(20)-(20) displayed negligible CDC (not shown), whereas 20-(74)-(74) was moderately active in Jeko-1 and Granta-519, but as potent as hA20 IgG in Daudi (not shown). 
     Apoptosis— 
     The ability of 20-(74)-(74) and 74-(20)-(20) to induce apoptosis was evaluated by flow cytometry using the Annexin V binding assay. In JeKo-1, both bispecific anti-CD20/CD74 HexAbs at 10 nM showed a statistically significant (P&lt;0.033) increase of 10-15% in Annexin V-positive cells over the various controls ( FIG. 2A ), which included untreated cells, cells treated with either parental antibody, and cells treated with both parental antibodies combined. Statistically significant increases of 10 to 25% in annexin V-positive cells were also observed for all four MCL patient samples (P&lt;0.008;  FIG. 2B ) and six of seven CLL patient samples (P&lt;0.03,  FIG. 2C ). Immunoblot results indicated that the treatment of JeKo-1 with the bispecific anti-CD20/CD74 HexAbs had no apparent effect on the expression levels of Bcl-2, Mcl-1, and Bax, but substantially reduced the amount of Bcl-xL (not shown). The lack of appreciable change in the expression level and cleavage of caspase 3, caspase 8, and caspase 9 (not shown) suggest that the bispecific anti-CD20/CD74 mediate a caspase-independent apoptosis, which was associated with 20 to 30% changes in mitochondrial membrane potential (Δψ m ) and about 30% increase in ROS in Granta-519 ( FIG. 2D ), and somewhat less in JeKo-1 (not shown). 
     Homotypic Adhesion and Actin Reorganization— 
     The 20-(74)-(74) and 74-(20)-(20) hexavalent DNL constructs, but not the parental antibodies, evoked in JeKo-1 a strong homotypic adhesion (not shown), which was prevented by latrunculin B, an inhibitor of actin polymerization. Similar results were observed for Granta-519, Mino and Raji (data not shown). Significant homotypic adhesion (&gt;40%) also could be induced in Jeko-1, but not in KMS-11 (a CD20-negative multiple myeloma line expressing a high level of CD74), by tositumomab (murine anti-human CD20 IgG 2b ) alone, or by the parental antibodies in the presence of a crosslinking antibody (Table 10). JeKo-1 and KMS-11 cells (2×10 6 /mL) were incubated with the indicated treatments for 2 and 24 h at 37° C. The values (%) shown were the mean from three different fields. KMS-11 is a multiple myeloma cell line with low CD20 expression and high CD74. nd, not determined. 
     Pretreatment of JeKo-1 with cytochalasin D, which is less toxic than latrunculin B and allows a longer period of incubation, decreased the extent of annexin V-positive cells ( FIG. 3A ) from 21±1% to 13±2% (P&lt;0.02) by 20-(74)-(74) or from 23±2% to 16±1% (P&lt;0.025) by 74-(20)-(20). These results correlate homotypic adhesion and actin reorganization with apoptosis in cell lines sensitive to treatment with the bispecific anti-CD20/CD74 HexAbs. Additional studies in JeKo-1 revealed that treatment with 20-(74)-(74) or 74-(20)-(20) induced actin to cluster at the cell-cell junction (not shown) and similar results could be produced either with B1 in the absence of a crosslinking antibody, or with rituximab, veltuzumab, or milatuzumab in the presence of a crosslinking antibody (not shown). However, neither 20-(74)-(74) nor 74-(20)-(20) appeared to co-localize with actin at the cell-cell junction when cells were co-stained with FITC-conjugated anti-human-Fc (not shown). 
     
       
         
           
               
             
               
                 TABLE 10 
               
             
            
               
                   
               
               
                 Homotypic adhesion induced in JeKo-1 by various 
               
               
                 antibodies and combinations of antibodies. 
               
            
           
           
               
               
               
            
               
                   
                 JeKo-1 
                 KMS-11 
               
            
           
           
               
               
               
               
               
            
               
                   
                 2 h 
                 24 h 
                 2 h 
                 24 h 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 μg/mL 
                   
                   
                   
                   
               
               
                 Untreated 
                 — 
                  5 ± 2 
                 &lt;8 
                 &lt;2 
                 &lt;4 
               
               
                 GAH 
                 20 
                  6 ± 3 
                 &lt;8 
                 &lt;3 
                 &lt;4 
               
               
                 hLL2 
                 5 
                  5 ± 2 
                 &lt;8 
                 &lt;2 
                 &lt;5 
               
               
                 hLL1 
                 5 
                  5 ± 3 
                 &lt;8 
                 &lt;3 
                 &lt;5 
               
               
                 hA20 
                 5 
                  5 ± 3 
                 &lt;14 
                 &lt;2 
                 &lt;4 
               
               
                 Rituximab 
                 5 
                 10 ± 4 
                 &lt;18 
                 &lt;2 
                 &lt;5 
               
               
                 B1 
                 5 
                 95 ± 4 
                 nd 
                 nd 
                 nd 
               
               
                 hLL2 + GAH 
                 5 + 20 
                  4 ± 2 
                 &lt;7 
                 &lt;2 
                 &lt;8 
               
               
                 hLL1 + GAH 
                 5 + 20 
                  8 ± 3 
                 &gt;95 
                 &lt;2 
                 &lt;6 
               
               
                 hA20 +GAH 
                 5 + 20 
                  55 ± 10 
                 &gt;95 
                 &lt;4 
                 &lt;4 
               
               
                 Rituximab + GAH 
                 5 + 20 
                 42 ± 8 
                 &gt;95 
                 &lt;4 
                 &lt;7 
               
               
                 hA20 + hLL1 
                 5 + 5  
                 10 ± 5 
                 &lt;18 
                 &lt;4 
                 &lt;4 
               
               
                 Rituximab + hLL1 
                 5 + 5  
                 21 ± 5 
                 &lt;24 
                 &lt;3 
                 &lt;8 
               
               
                 hA20 + hLL1 + GAH 
                 5 + 5 + 20 
                 60 ± 4 
                 &gt;95 
                 &lt;4 
                 &lt;9 
               
               
                 Rituximab + hLL1 + GAH 
                 5 + 5 + 20 
                  56 ± 12 
                 &gt;95 
                 &lt;2 
                 &lt;8 
               
               
                   
                 (nM) 
               
               
                 B1 
                 10 
                 90 ± 5 
                 &gt;95 
                 &lt;3 
                 &lt;9 
               
               
                 20-(74)-(74) 
                 10 
                 90 ± 5 
                 &gt;95 
                 &lt;4 
                 &lt;8 
               
               
                 74-(20)-(20) 
                 10 
                 90 ± 5 
                 &gt;95 
                 &lt;2 
                 &lt;9 
               
               
                 74-(74)-(74) 
                 10 
                 nd 
                 nd 
                 nd 
                 nd 
               
               
                 20-(20)-(20) 
                 10 
                 16 ± 2 
                 &lt;21 
                 &lt;3 
                 &lt;5 
               
               
                 22-(20)-(20) 
                 10 
                 18 ± 4 
                 &lt;20 
                 &lt;3 
                 &lt;8 
               
               
                 20-(22)-(22) 
                 10 
                 15 ± 4 
                 &lt;24 
                 &lt;2 
                 &lt;6 
               
               
                   
               
            
           
         
       
     
     Involvement of Lysosomes— 
     HexAb-mediated apoptosis could be reduced effectively with concanamycin A or bafilomycin A1, both functioning by blocking lysosomal acidification through selective inhibition of the V-type ATPase (Drose &amp; Altendorf, 1997 , J Exp Biol  200:1-8). As shown in  FIG. 3B , treatment of JeKo-1 with concanamycin A (10 nM) or bafilomycin A1 (50 nM) before the addition of either 20-(74)-(74) or 74-(20)-(20) largely decreased the extent of annexin V-positive cells. Further, a sizable enlargement of the lysosomal compartments by the two bispecific anti-CD20/CD74 HexAbs was demonstrated using flow cytometry with a fluorescent acidotropic probe, LYSOTRACKER® Red DND-99 (not shown). These results implicate a causal role of lysosomes in cell death, and are supported by fluorescence microscopic evidence of lysosomal membrane permeabilization and release of cathepsin B into the cytosol (not shown). 
     Effect on MAP Kinases, Src, p65/NF-κB, and Akt— 
     The bispecific anti-CD20/CD74 HexAbs induced rapid and sustained activation of ERK and JNK kinases in Jeko-1. For 74-(20)-(20) and 20-(74)-(74) phosphorylated ERKs and JNK, respectively, could be detected within 30 min (not shown), which persisted for the next 6 h and returned to basal levels by 24 h (not shown). In contrast, no phosphorylation of ERKs and JNK was observed in those cells incubated with both parental antibodies (not shown). Due to the high expression of the p38 MAP kinase in Jeko-1, we were unable to determine whether its level had changed upon treatment with the bispecific HexAbs. 
     Select signals upstream and downstream of ERKs and INK were also found to be modulated by treating JeKo-1 with the bispecific anti-CD20/CD74 HexAbs. Pertinent results include the ability of both HexAbs to induce a larger decrease (˜60%) of the upstream phospho-Src than that of the parental hA20 MAb (˜30%) (not shown), and the effective inhibition of the downstream p65/NF-κB from nuclear translocation by both HexAbs (not shown). We also observed that the bispecific HexAbs notably reduced the level of constitutively activated Akt in JeKo-1 (not shown). 
     Ex Vivo Depletion of JeKo-1 and Normal B Cells from Human Whole Blood— 
     When evaluated at high concentrations (10 and 25 nM) in whole blood spiked with JeKo-1 cells, we observed &gt;90% depletion of JeKo-1 cells for 20-(74)-(74), hA20, and hA20+hLL1, but no more than 50% depletion for 74-(20)-(20), and &lt;20% depletion for hLL1 or the non-targeting hMN-14 (anti-CEACAM5) control antibody ( FIG. 4A . upper panel). The depletion of normal B cells, on the other hand, was similar for the two HexAbs, in the range of 50 to 70% for 20-(74)-(74) and 60 to 75% for 74-(20)-(20), with higher depletion (80 to 90%) attained by hA20 or the combination of hA20 and hLL1 ( FIG. 4A , lower panel). The apparently higher potency of 20-(74)-(74) as compared to 74-(20)-(20) in depleting JeKo-1 cells from whole blood prompted subsequent studies using three lower concentrations (0.1, 0.5 and 1 nM), and the results shown in  FIG. 4B  (upper panel) and  FIG. 4C  (upper panel) confirmed the higher activity of 20-(74)-(74) than 74-(20)-(20) in depleting JeKo-1 cells from whole blood, since 20-(74)-(74) at 0.1 nM was able to deplete 70% of JeKo-1 cells, whereas 74-(20)-(20) at 25 nM could not achieve more than 50% depletion. The high potency of 20-(74)-(74) was also manifested by its ability to deplete 40 to 50% of normal B cells at 0.1 to 1 nM ( FIG. 4B , lower panel), a blood concentration that should be easily attainable clinically. Under the same conditions, 74-(20)-(20) at 0.1 to 1 nM depleted 10% or less of normal B cells ( FIG. 4C , lower panel). It is noted that the ability of 20-(74)-(74) to deplete either JeKo-1 or normal B cells from whole blood is comparable, not superior, to that of hA20 or the combination of hA20 and hLL1. 
     In Vivo Studies— 
     To evaluate the efficacy of HexAbs in vivo, mice bearing disseminated JeKo-1 were treated with increasing doses (3.7, 37, or 370 μg) of either 20-(74)-(74) or 74-(20)-(20) given twice weekly for two weeks. Survival curves for the various treatment groups are shown in  FIG. 5 . Saline control mice succumbed to disease progression by day 34. Both treatments at all three doses significantly improved survival compared to the control animals (P=0.0001). Mice treated with the highest dose of 74-(20)-(20) had an approximate 30% increase in median survival over saline controls (43.5 days vs. 34 days; P=0.0001). A 60% increase in median survival (MST=53 days) over saline controls was observed in mice treated with 20-(74)-(74) at 370 μg (P=0.0001). Both HexAbs given at 370 μg were more effective than the two lower doses (P&lt;0.0143). However, there were no significant differences between mice treated with 20-(74)-(74) and 74-(20)-(20) at the same dose. 
     Discussion 
     CD74 is the cell surface form of the HLA class II-associated invariant chain, which plays a key role as a chaperone protein in antigen presentation by HLA-DR to Th cells (Weenink &amp; Gautam, 1997 , Immunol Cell Biol  75:69-81). In addition, CD74 mediates macrophage migration inhibitory factor (MIF)-induced signal transduction as its cognate membrane receptor (Leng et al., 2003 , J Exp Med  197:1467-1476), resulting in activation of ERK1/2 and protection from p53-dependent apoptosis in a process that requires CD44 as a signaling component and involves PKA and c-Src (Shi et al., 2006 , Immunity  25:595-606). Moreover, the intracellular domain of CD74 (CD74-ICD) released from intramembrane proteolysis in the endocytic compartments can activate NF-κB to induce B-cell maturation (Becker-Herman et al., 2005 , Mol Biol Cell  16:5061-5069), and this activity is further enhanced by stimulating CD74 with an agonistic antibody or MIF, either of which augments CD74-ICD release, increases Bcl-xL expression, and elevates the phosphorylation of both Akt and Syk (Starlets, 2006 , Blood  107:4807-4816). In CLL cells (Binsky et al., 2007 , Proc Natl Acad Sci USA  104:13408-13413) and B-lymphocytes (Gore et al., 2008 , J Biol Chem  283:2784-2792), binding of CD74 to MIF initiates a signaling cascade that promotes cell survival via activation of NF-κB and secretion of IL-8, which can be inhibited by the antagonistic anti-CD74 MAb, milatuzumab (Binsky et al., 2007 , Proc Natl Acad Sci USA  104:13408-13413; Shachar &amp; Haran 2011 , Leuk Lymphoma  52:1446-1454), thus further substantiating the rationale to develop milatuzumab-based therapeutic agents for the treatment of cancer (Stein et al., 2007 , Clin Cancer Res  13:5556s-5563s) and autoimmune disease (Borghese &amp; Clanchy, 2011 , Exp Opin Ther Targets  15:237-251) by blocking the CD74/MIF pathway. 
     The commercial success of rituximab in treating certain B-cell malignancies and autoimmune disorders has stimulated much interest in developing new anti-CD20 antibodies with improved efficacy, as well as elucidating the in vitro and in vivo mechanisms of action for rituximab and its analogues (Lim et al., 2010, Haematologica 95:135-143). At present, next-generation anti-CD20 MAbs include human and humanized forms, with some claiming enhanced potency by antibody reengineering (Pawluczkowycz et al., 2009 , J Immunol  183:749-758; Mossner et al., 2010 , Blood  115:4393-4402). Although CD20 is a well-validated therapeutic target and despite more than 10 years of clinical use of rituximab and an expansive preclinical literature on the use of anti-CD20 MAbs in lymphoma models in vitro and in vivo, how rituximab or other anti-CD20 MAbs kill lymphoma cells is still being debated (Glennie et al., 2007 , Mol Immunol  44:3823-3837) among the three principal mechanisms proposed, CDC, ADCC, and direct toxicity induced by signaling. Functional differences, as revealed by a variety of assays such as induction of homotypic adhesion, stimulation of calcium mobilization, association with lipid rafts, capability for effective CDC, ADCC or both, and requirement of hypercrosslinking for direct in vitro cytotoxicity, have been used (Cragg et al., 2003 , Blood  101:1045-52) to classify anti-CD20 MAbs into type I, represented by rituximab, or type II, represented by tositumomab, with some data indicating that type II MAbs appear to outperform type I in preclinical models (Cardarelli et al., 2002 , Cancer Immunol Immunother  51:15-24; Beers et al., 2008 , Blood  112:4170-4177), which awaits confirmation in patients. We have previously noted (Rossi et al., 2008 , Cancer Res  68:8384-8392) that one effective approach to converting a type I anti-CD20 MAb to a type II can be achieved by making the type I MAb multivalent, as shown by the HexAb generated from the type I veltuzumab, 20-(20)-(20), which exhibits biological properties attributable to both type II (for example, negative for CDC and calcium mobilization; positive for anti-proliferation, apoptosis, and homotypic adhesion) and type I (for example, positive for trafficking to lipid rafts). 
     The strategy to target both CD20 and CD74 with distinct MAbs was reported recently in a preclinical study using a combination of milatuzumab and rituximab plus a secondary crosslinking Ab in MCL lines and primary tumor cells (Alinari et al., 2011 , Blood  117:4530-41), which showed that the treatment resulted in rapid cell death, generation of ROS, loss of mitochondria membrane potential, strong homotypic adhesion, and inhibition of p65 nuclear translocation. The observed cell death was attributed to a nonclassical apoptotic mechanism, because it lacks evidence of autophagy and caspase-activation, but requires the participation of actin and lysosomes. In the current study, we evaluated the potential of two anti-CD20/CD74 HexAbs for the therapy of MCL, and observed similar intracellular events to those obtained with milatuzumab and rituximab combined in the presence of a secondary crosslinking Ab, which include generation of ROS, loss of mitochondria membrane potential, inhibition of p65 nuclear translocation, absence of autophagy, and caspase-independence. Surprisingly, the two anti-CD20/CD74 HexAbs, were capable of manifesting direct in vitro cytotoxicity in 3 MCL, 2 NHL, and 2 CLL cell lines, as well as inducing a significantly higher number of annexin V-positive cells in primary tumor samples from MCL and CLL patients, compared to untreated controls. 
     We also investigated the signaling pathways triggered in JeKo-1 cells by the two anti-CD20/CD74 HexAbs. Our findings suggest that the rapid and sustained activation of ERKs and JNK may contribute to cell death (Zhuang &amp; Schnellmann, 2006 , J Pharmacol Exp Ther  319:991-997), as shown in Raji and SU-DHL4 treated with tositumomab and radiation (Ivanov et al., 2008 , Clin Cancer Res  14:4925-4934), in renal epithelial cells during oxidative injury (Di Mari et al., 1999 , Am J Physiol  277:F195-F203), and in Raji and other B-lymphoma lines (including Jeko-1 and Granta-519) upon ligation to hL243 (anti-HLA-DR) MAb (Stein et al., 2010 , Blood  115:5180-5190). We also found that both anti-CD20/CD74 HexAbs disrupt the NF-κB pathway by inhibiting the translocation of p65 from cytosol to the nucleus, and downregulate Bcl-xL, which may further promote cell death. 
     Ligation of various antibodies with receptors such as HLA-DR, CD19, CD20, CD39, CD40, CD43, and others has been observed to induce homotypic adhesion in a panel of B-cell lymphoma lines (Kansas &amp; Tedder, 1991 , J Immunol  147:4094-4102). The anti-CD20/CD74 HexAbs, like the anti-CD20/CD22 HexAbs, also induced strong homotypic adhesion in JeKo-1 cells that was not observed with the parental MAbs alone or in combination. The HexAb-induced homotypic adhesion was blocked by inhibitors of actin polymerization, which also reduced cell death. Similar results have been observed with the combination of rituximab and milatuzumab in the presence of secondary crosslinking antibody in MCL lines (Alinari et al., 2011 , Blood  117:4530-41). Our studies also indicate that the induction of homotypic adhesion by the anti-CD20/CD74 HexAbs is independent of their susceptibility to internalization, and neither classical apoptosis nor autophagy is involved in cell death, which appeared to closely resemble the actin- and lysosome-dependent cell death evoked by tositumomab and hL243 in Raji and SU-DHL4 (Ivanov et al., 2009 , J Clin Invest  119:2143-2159). 
     When examined ex vivo using normal human blood spiked with JeKo-1 cells, 20-(74)-(74) depleted JeKo-1 cells more effectively than the parental MAb hA20, while hLL1 and 74-(20)-(20) did not show much activity. This improved efficacy may result from the fact that 20-(74)-(74), but not 74-(20)-(20), displays effector functions, as determined by ADCC and CDC. Both HexAbs, nevertheless, showed reduced but similar potency in depleting normal B cells, which could be due to a lower expression of CD20 or CD74 antigens, as well as the more mature cell type. 
     In summary, bispecific anti-CD20/CD74 HexAbs, as represented by 20-(74)-(74) and 74-(20)-(20), were successfully generated and their potential for therapy of MCL evaluated and demonstrated in preclinical studies. The key findings are as follows. (1) Effective inhibition of proliferation requires juxtaposing CD20 and CD74 in close proximity. (2) The observed direct in vitro cytotoxicity is accompanied by extensive homotypic adhesion, relocation of actin to the cell-cell junction, notable lysosomal enlargement, release of cathespin B into the cytosol, loss of mitochondria membrane potential, generation of ROS, deactivation of the PI3K/Akt signaling pathway, as well as rapid and sustained activation of ERK and JNK MAPKs. (3) Homotypic adhesion can be a first indicator for determining whether a certain antibody or combination of antibodies will display toxicity against antigen-expressing hematological cells. (4) Both 20-(74)-(74) and 74-(20)-(20) will be of use in additional B-cell malignancies, in particular CLL, and in autoimmune disease. These compounds constitute a new therapeutic class of anticancer antibodies. 
     Example 12 
     Anti-CD74 Antibodies Improve the Efficacy of Standard Treatments for B Cell Malignancies 
     Milatuzumab (humanized anti-CD74 monoclonal antibody) is in clinical evaluation for therapy of multiple myeloma, CLL and NHL (Berkova et al., 2010, Expert Opin Invest Drugs 19:141-49). CD74, the MHC class-II chaperone molecule, also functions as the cellular receptor for the proinflammatory cytokine, macrophage migration-inhibitory factor, and initiates a signaling cascade resulting in proliferation and survival (e.g., Leng et al., 2003, J Exp Med 197:1467-76). Preclinically, milatuzumab demonstrates therapeutic activity against various B-cell malignancies when used alone (Berkova et al., 2010, Expert Opin Invest Drugs 19:141-49), and the therapeutic efficacies of bortezomib, doxorubicin, and dexamethasone are enhanced in multiple myeloma cell lines when given combined with milatuzumab (Stein et al., 2009, Clin Cancer Res 15:2808-17). Milatuzumab acts through distinct mechanisms from rituximab, and exhibits different expression and sensitivity profiles. We examined the effects of milatuzumab given in combination with rituximab or fludarabine in human NHL, CLL, and ALL cell lines. 
     Methods 
     Three human NHL (WSU-FSCCL, Raji, and RL); two ALL (MN60 and REH), and two CLL (MEC-1 and WAC) cell lines were tested, with evaluation of therapeutic efficacies of milatuzumab and fludarabine performed in the NHL and CLL cell lines. The cell lines were selected to evaluate a range of different CD74 and CD20 expression levels (Table 11). 
     
       
         
           
               
             
               
                 TABLE 11 
               
             
            
               
                   
               
               
                 Cell surface expression of CD74 and CD20 (mean fluorescence) 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 Isotype control 
                 CD74 
                 CD20 
               
               
                   
                   
                 (hMN14, 
                 (hLL1, 
                 (hA20, 
               
               
                   
                 Cell line 
                 anti-CEA) 
                 milatuzumab) 
                 veltuzumab) 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 NHL 
                 Raji 
                 11.6 
                 318.6 
                 760.4 
               
               
                   
                 RL 
                 6.2 
                 56.0 
                 264.5 
               
               
                   
                 WSU-FSCCL 
                 5.3 
                 20.9 
                 36.6 
               
               
                 ALL 
                 REH 
                 3.0 
                 70.6 
                 15.0 
               
               
                   
                 MN60 
                 8.4 
                 57.0 
                 719.4 
               
               
                 CLL 
                 MEC-1 
                 5.4 
                 41.4 
                 270.5 
               
               
                   
                 WAC 
                 5.2 
                 17.4 
                 210.6 
               
               
                   
               
            
           
         
       
     
     Results 
     Anti-proliferative activity was augmented in vitro when milatuzumab and rituximab were combined ( FIG. 7 ). For example in WSU-FSCCL cells, which are relatively insensitive to rituximab, inhibition of proliferation in the presence of 33.3 nM rituximab increased from 12.6±3.7% in the absence of milatuzumab to 85.5±0.0% (P=0.023) in the presence of 33.3 nM milatuzumab ( FIG. 7 ). In Raji, a more sensitive cell line, inhibition of proliferation in the presence of 22.2 nM rituximab increased from 64.8±1.3% without milatuzumab to 86.6±0.9% (P=0.018) with 22.2 nM milatuzumab ( FIG. 7 ). Significant increases in the anti-proliferative activity of rituximab were similarly observed in all but one of the tested NHL, CLL, and ALL cell lines ( FIG. 7 ), with the exception of REH, which was not sensitive to killing by either milatuzumab or rituximab. Unlike rituximab, milatuzumab induced little or no ADCC or CDC (not shown). However, in vitro exposure of cells to milatuzumab did not affect rituximab mediated ADCC or CDC (not shown). 
     The effects of milatuzumab on mitochondrial membrane potential were examined using an alamar blue assay. Alamar blue (10%) was added to wells 24 h after each period of incubation and changes in alamar blue reduction were measured every fifteen minutes for a total of 4 hours. Rituximab-resistant cell lines were generated from the Raji parental cell lines by exposing cells to an escalating dose of rituximab (0.1 to 128 μg/ml), either without human serum (Raji 2R) or in the presence of human serum (Raji4RH). The combination of milatuzumab and rituximab was observed to result in a more potent decrease in the mitochondrial potential in rituximab-sensitive cell lines, but not in rituximab-resistant cell lines. 
     It was found that milatuzumab increased the efficacy of fludarabine-induced cytotoxicity in 3 NHL and 2 CLL cell lines ( FIG. 8 ). For example, in Raji cells, which are relatively insensitive to fludarabine, inhibition of proliferation in the presence of 4 nM fludarabine increased from no inhibition in the absence of milatuzumab to 76.9±0.7% (P=0.009) in the presence of 33.3 nM milatuzumab ( FIG. 8 ). In WSU-FSCCL cells, a more fludarabine-sensitive cell line, inhibition of proliferation in the presence of 0.8 nM fludarabine increased from 41.3±0.3% in the absence of milatuzumab to 79.7±0.1% (P&lt;0.0001) with 33.3 nM milatuzumab ( FIG. 8 ). 
     Conclusions 
     Milatuzumab and other antagonistic anti-CD74 antibodies can significantly add to the efficacy of currently approved therapies, such as fludarabine and rituximab, for B cell diseases, including NHL, CLL and ALL. 
     It will be readily apparent to one skilled in the art that varying substitutions and modifications may be made to the invention disclosed herein without departing from the scope and spirit of the invention. Thus, such additional embodiments are within the scope of the present invention.