bluuebunny/crossref_metadata_2025 huggingface dataset:
The importance of dominant negative effects of amino acid side chain substitution in peptide-MHC molecule interactions and T cell recognition.
Authors: Boehncke W H , Takeshita T , Pendleton C D , Houghten R A , Sadegh-Nasseri S , Racioppi L , Berzofsky J A , Germain R N
Published: December 2022

Previous studies on the role of specific residues of the peptide or MHC molecule in Ag presentation have revealed the sensitivity of this complex system to even small changes in structure. In our study, we have analyzed the effect of amino acid substitution in a major CD4+ T cell determinant (T1) of HIV-1 gp160 on binding and recognition in the context of various E alpha E beta MHC class II molecules. Individual alanine substitutions at all but three positions had little or no negative effect on either MHC binding or recognition by a specific T hybridoma, whereas substitutions with larger side chains often diminished reactivity. A poly-alanine peptide containing only four of the original residues was an effective MHC class II binder and in vivo immunogen, although lacking the ability to stimulate the hybridoma. Replacement of a glutamic acid in T1 with alanine or a size-conservative, uncharged glutamine, but not a negatively charged aspartic acid produced a peptide at least 100-fold more potent than the parent peptide, indicating an inhibitory effect of the negative charge. Conversely, substitution of a glutamic acid for valine at position 29 in the floor of the peptide binding site of the E alpha E beta molecule decreased functional presentation of this peptide by more than 2 logs. However, these two effects of glutamic acid were not complementary and were mediated by distinct mechanisms, as the change in the peptide altered the extent of binding to class II, but the change in the MHC molecule decreased recognition without inhibiting peptide binding. Taken together, the data all suggest the conclusion that changes in side-chains of peptides and MHC molecules affect Ag presentation and T cell stimulation most often by introducing dominant negative or interfering groups that prevent or alter the pattern of binding events primarily mediated by a very limited number of other residues in the Ag or presenting molecule. These results have important implications for understanding the biochemistry of peptide-MHC-TCR interactions and for the possible design of vaccines both more potent and less subject to allele-specific limitations on immunogenicity.
Role of mouse VH10 and VL gene segments in the specific binding of antibody to Z-DNA, analyzed with recombinant single chain Fv molecules.
Authors: Brigido M M , Polymenis M , Stollar B D
Published: December 2022

A plasmid vector was constructed for the expression of a single chain Fv domain of mouse mAb to Z-DNA (antibody Z22), which is encoded by VH10 and V kappa 10 gene family members along with Dsp2, JH4, and J kappa 4 segments. The vector coded for a PhoA secretion signal, VH segment, flexible peptide linker, VL segment, (His)5, and a protein A domain. Unique restriction sites allowed exchange of the segments as cassettes. Bacteria transformed with the vector secreted soluble recombinant Fv with specific Z-DNA-binding activity. When the L chain of Z22 was replaced with a library of splenic VL cDNA from a mouse immunized with Z-DNA, only a light chain closely resembling that of the original Z22 (differing at six amino acid positions) yielded Fv with Z-DNA-binding activity. The Fv with this L chain replacement had a lowered affinity, but remained selective for Z-DNA. Replacement of the Z22 H chain with a mixture of 11 VH10-encoded H chains yielded two Z-DNA binding clones, but they bound B-DNA and denatured DNA as well as Z-DNA. The replacement clones indicate the importance of the H chain CDR3 and particular VH-VL combinations in formation of specific antibodies to Z-DNA.
Structural analysis of the CD11b gene and phylogenetic analysis of the alpha-integrin gene family demonstrate remarkable conservation of genomic organization and suggest early diversification during evolution.
Authors: Fleming J C , Pahl H L , Gonzalez D A , Smith T F , Tenen D G
Published: December 2022

CD11b is a member of the beta 2 subfamily of the human leukocyte integrins. Its expression is limited to mature myeloid and NK cells and is up-regulated during the course of granulocytic and monocytic differentiation. The CD11b/CD18 (Mo1) heterodimer promotes adhesion of granulocytes and monocytes to C3bi-coated bacteria and endothelial cells. In an attempt to relate the exon structure to the known functional domains, as well as to identify and study cis-acting elements that are involved in its tissue-specific expression, we have isolated genomic clones encoding CD11b, deduced the exon/intron organization, and determined the transcriptional start site. The CD11b gene spans 55 kb and is encoded by 30 exons. Its structure closely resembles that of CD11c, another of the three leukocyte integrin alpha-chains, and suggests that these two genes arose by a gene duplication event. Furthermore, comparison of the CD11b gene structure with that of platelet glycoprotein IIb and Drosophila PS2 suggest how the human leukocyte integrins evolved and dispersed during the course of evolution.
IL-2 contributes to the IL-5 response in granulomas from mice infected with Schistosoma mansoni.
Authors: Metwali A , Elliott D , Mathew R , Blum A , Weinstock J V
Published: December 2022

Th cells within the granulomas of murine schistosomiasis mansoni produce IL-5, which is essential for granuloma eosinophil growth and development. The mechanisms regulating granuloma IL-5 production are unknown. The granulomas also make IL-2 in small quantities. rIL-2 therapy stimulates eosinophilia and IL-5 synthesis. Therefore, we studied the effect of IL-2 on IL-5 production within the liver granulomas of murine Schistosoma mansoni. Dispersed granuloma cells and intact granulomas cultured in vitro released IL-5. Adding anti-IL-2 or anti-IL-2R to the cultures, to block IL-2 activity, significantly inhibited IL-5 production. However, supplementing the cultures with small quantities of rIL-2 markedly stimulated IL-5 release in a dose-dependent fashion. Blocking anti-IL-4 mAb had no effect. Also, granuloma T cells were isolated by FACS. These highly purified T cells produced IL-5 both in the presence and absence of plate-bound anti-CD3. Once again, the IL-5 production was dependent on IL-2. The requirement of IL-2 for normal IL-5 production was not dependent on an IL-2-induced expansion of the IL-5-producing, T lymphocyte population. Thus, IL-2 mediates T cell interactions within the granuloma that regulate granuloma IL-5 secretion.
Repertoire diversity of antibody response to bacterial antigens in aged mice. III. Phosphorylcholine antibody from young and aged mice differ in structure and protective activity against infection with Streptococcus pneumoniae.
Authors: Nicoletti C , Yang X , Cerny J
Published: December 2022

Aging in mice is accompanied by qualitative changes in the antibody repertoire to phosphorylcholine (PC), a natural epitope of certain pneumococci. The PC-specific mAb from young/adult (2-4 mo) BALB/c mice are uniformly encoded by the canonical IgV genes of T15 family, whereas the antibody from aged mice (> or = 20 mo) are molecularly heterogeneous, being encoded by various VH and VL genes of non-T15 families. Interestingly the young/adult and aged BALB/c mice produce comparable amounts of antibodies to PC regardless of the molecular shift in the antibody repertoire. This finding prompted our study on the relative ability of PC antibodies from young and aged donors to protect mice against virulent infection with type 3 pneumococci. Passive administration (i.p.) of pooled, PC-specific mAb generated from young donors (all from the T15 Ig gene family) protected the recipients against subsequent i.p. challenge with a lethal dose of Streptococcus pneumoniae strain WU2, in a dose-dependent manner. In contrast, a mixture of PC mAb from aged donors (all from non-T15 families) failed to protect the mice against the infection, even at the highest amount of administered (100 micrograms of mAb/recipient). Average affinity of the aged mAb for the free hapten (PC-chloride) as well as their binding to the bacteria was lower than that of the young mAb. Similarly, affinity-purified serum PC antibody from S. pneumoniae vaccine-immunized young mice afforded a measurable degree of passive protection against the pneumococcal infection whereas a similar dose of serum PC antibody from aged mice did not. Further experiments showed that PC mAb from young donors were equally protective in either young or aged recipients challenged with the bacteria. These results demonstrate that the aged immune system may, in some instances, produce high levels of antibody that are structurally different and less protective against microbial infection.
Mobilization of different arachidonate pools and their roles in the generation of leukotrienes and free arachidonic acid during immunologic activation of mast cells.
Authors: Fonteh A N , Chilton F H
Published: December 2022

Immunologic activation of mast cells leads to the mobilization of arachidonic acid (AA) from membrane phospholipids and the subsequent conversion of this AA to bioactive products. The objective of our study was to determine if segregated pools of AA-containing phospholipids within mast cells serve as independent sources of AA. Initial studies indicated that the appearance of free AA occurred rapidly (maximal level formed within 1 min) within supernatant fluids of Ag-stimulated mast cells and was kinetically different from the formation of leukotriene (LT) B4 or LTC4. To examine whether free AA and leukotrienes were mobilized from different sources, AA-containing phospholipids of mast cells were labeled with [14C] and [3H] AA such that all major subclasses (1-acyl-1-alkyl-1-alk-1'-enyl) of phospholipids contained different ratios of [3H] to [14C] (sp. act. ratios (SAR)). Mast cells were then stimulated with Ag and the SAR of cellular AA, extracellular AA and extracellular LTC4, LTB4, 6-trans LTB4, were determined. The SAR were uniform in all LT and mimicked the ratio found in cellular AA. By contrast, the SAR of AA released into supernatant fluids was twofold lower than that of LT. This indicated that AA released as free fatty acid clearly was derived from a different lipid pool than AA that formed LT. Although it was apparent that the pools which gave rise to AA and LT were different, defining phospholipid(s) that constitute these distinct pools proved more difficult. The SAR of LT suggested that their cellular precursor AA could have been derived from several phospholipid subclasses; however, the SAR in phosphatidylcholine and phosphatidylinositol most closely matched the LT. The SAR of AA in supernatant fluids implied that it was derived, in part, from phosphatidylethanolamine subclasses. Taken together, these data suggest that there are at least two different pools of AA that are mobilized in mast cells during Ag activation.
Regulation of HIV-1 expression by cytokine networks in a CD4+ model of chronic infection.
Authors: Butera S T , Roberts B D , Folks T M
Published: December 2022

Using the CD4+ model of chronic HIV-1 infection, OM-10.1, we investigated the influence of TNF-alpha regulatory networks on induced viral expression. Previously, OM-10.1 cultures were characterized to respond to exogenous TNF-alpha, as nearly 100% of the cells were activated to express HIV-1 within 24 h. In this study, OM-10.1 cells were pulse-treated, by applying exogenous factors for short periods of time and then washing, to determine if autocrine TNF-alpha could sustain HIV-1 activation in the absence of additional exogenous stimulation. After a TNF-alpha pulse treatment, the progressive increase of HIV-1-expressing OM-10.1 cells was prevented by the continuous presence of anti-TNF-alpha mAb. The inductive activity of supernatant from TNF-alpha pulse-treated OM-10.1 cultures was completely removed by absorption on immobilized anti-TNF-alpha mAb. In addition, TNF-alpha pulse-treated OM-10.1 cells activated HIV-1 expression in untreated OM-10.1 cells when cultured across a permeable membrane indicating paracrine effects. Interestingly, if TNF-alpha pulse-treated OM-10.1 cells were further pulse-treated with anti-TNF-alpha mAb, a marked reduction in autocrine TNF-alpha was observed although the level of newly synthesized TNF-alpha mRNA remained unaffected. A similar degree of inhibition over autocrine TNF-alpha production was observed when soluble TNF receptors were used as the second pulse treatment in these experiments. Although the applicability of these results to in vivo chronically HIV-1-infected cells remains to be realized, these results do indicate that activated HIV-1 expression can be influenced by self-perpetuating mechanisms during periods of limited exogenous stimulation. Furthermore, physiologic mechanisms involving soluble cytokine receptors that counteract autocrine and paracrine activation of HIV-1 expression are shown here to play a regulatory role.
Repertoire of neutralizing human monoclonal antibodies specific for the V3 domain of HIV-1 gp120.
Authors: Gorny M K , Xu J Y , Karwowska S , Buchbinder A , Zolla-Pazner S
Published: December 2022

HIV infection induces antibodies that mediate neutralization of cell-free virus and may protect against viral infection. Neutralizing human mAb that bind to the third hypervariable domain (V3) of gp120 have been generated from PBL of HIV-seropositive subjects. Twelve such mAb recognize 9 different epitopes spanning an 11 amino acid stretch at the tip of the V3MN loop. The epitopes of an additional two mAb have not been precisely determined but occur within a 15-mer peptide around the tip of the V3 loop. Eleven of 13 mAb are reactive with at least one other V3 peptide besides MN, indicating that cross-reactivity is a common phenomenon amongst anti-V3 antibodies. All the mAb achieved 50% neutralization of HIVMN at antibody concentrations of 12 to 4700 ng/ml. Two mAb, which recognized epitopes at the top of the V3 loop, GPGR and GRAF, neutralized strains as divergent as MN and IIIB. The affinities of all mAb tested were shown to be substantially higher for the rgp120 than for a 23-mer peptide from the V3 loop of the homologous strain. A significant inverse correlation was demonstrated between affinities and the 50% neutralizing doses for HIVMN.
Studies of T cell deletion and T cell anergy following in vivo administration of SEB to normal and lupus-prone mice.
Authors: Scott D E , Kisch W J , Steinberg A D
Published: December 2022

This study examines the responses of lupus-prone NZB, (NZB x NZW) F1, BXSB, MRL-lpr/lpr and control mice (H-2 and Mls matched) to in vivo administration of the superantigen staphylococcal enterotoxin B (SEB). Two weeks after i.v. administration of 500 micrograms SEB, CD4+V beta 8+ lymph node T cells were deleted equivalently by lupus-prone and control mice. However, IE+ strains deleted a greater proportion (47% to 77%) of their CD4+V beta 8+ cells than did IE- strains (24% to 27%). CD8+V beta 8+ cells were deleted less than CD4+V beta 8+ cells by injection of 500 micrograms SEB. IE- strains failed to delete CD8+V beta 8+ cells, whereas six of seven IE+ strains deleted > 25% of their CD8+V beta 8+ cells. IE+ MRL-lpr/lpr mice showed some impairment in deletion: they failed to delete CD8+V beta 8+ cells at all doses of SEB and had reduced deletion of CD4+V beta 8+ cells at low doses of in vivo SEB (10 and 50 micrograms). Peripheral expansion of the intrathymically deleted V beta 7 TCR family was not observed in lupus-prone mice 2 wk after 500 micrograms in vivo SEB. In vitro restimulation with SEB of mice previously injected with 500 micrograms SEB demonstrated anergy in T cells from all strains, including the IE- and MRL-lpr/lpr. This result contrasts with previous reports of tolerance defects in lupus-prone strains using B cell read-out assays as measures of tolerance. The present study demonstrates that there is no global defect in peripheral T cell deletion or anergy in lupus-prone mice to the superantigen SEB. Although additional Ag would need to be studied, these experiments raise the possibility that some reported tolerance defects in lupus-prone strains may reflect excessive B cell responses to relatively normal T cell signals.
Activation of alveolar macrophages in asymptomatic HIV-infected individuals.
Authors: Buhl R , Jaffe H A , Holroyd K J , Borok Z , Roum J H , Mastrangeli A , Wells F B , Kirby M , Saltini C , Crystal R G
Published: December 2022

After the initial infection with HIV, there is evidence of immune dysfunction despite an apparent normal clinical state. In the context that the lung is a major site affected by opportunistic infection during the progression of this immune dysfunction, and that some components of the immune system are activated during early HIV infection, we hypothesized that there may be activation of alveolar macrophages (AM), a key component of the pulmonary host defense system, during the asymptomatic phase of HIV infection. Compared to normals, in HIV-infected individuals the class II MHC molecules DR, DQ, and DP were all expressed more frequently and in greater cell surface density on AM (p < 0.03, all comparisons), and there was increased spontaneous release of superoxide anion (O2-.) by AM (p < 0.002). To gain insight into whether the activation of the AM was an inherent property of the cells or dependent on the in vivo milieu, AM were evaluated after 24 h in culture for O2-. release. In contrast to the findings in fresh AM, after 24 h in culture, O2-. release by HIV AM was not different from normals (p > 0.7), suggesting that these AM had been activated in vivo. To assess whether IFN-gamma could be mediating these effects, mRNA levels of the IP-10 gene (a gene specifically induced by increased concentrations of IFN-gamma) were quantified in AM. Strikingly, the IP-10 gene was expressed only in AM of HIV-seropositive individuals, suggesting the AM had been exposed to IFN-gamma in vivo. Overall, these observations are consistent with the concept that the HIV-seropositive state is associated with activation of AM, in part due to local exposure to IFN-gamma.
Identification of multiple T cell epitopes on Bet v I, the major birch pollen allergen, using specific T cell clones and overlapping peptides.
Authors: Ebner C , Szépfalusi Z , Ferreira F , Jilek A , Valenta R , Parronchi P , Maggi E , Romagnani S , Scheiner O , Kraft D
Published: December 2022

Eleven T cell clones (TCC) with specificity for Bet v I were established from the peripheral blood of six birch pollen allergic donors. Bet v I is the major allergen of birch (Betula verrucosa) pollen and shows high homology to the major allergens of pollens of other trees within the order fagales (hazel, alder, hornbeam, oak, etc.), which represent important inhalant allergens in the northern hemisphere. The TCC were shown to react with purified natural, as well as with purified recombinant Bet v I. All clones showed the helper cell phenotype (CD3+CD4+) and expressed the TCR-alpha/beta. The cytokine production pattern in response to stimulation with allergen resulted in enhanced production of IL-4 in 9 of 11 clones. The clones were used for T cell epitope mapping on the Bet v I molecule. For this purpose, peptides with a length of 12 amino acids each and overlapping for 10 residues were synthesized following the amino acid sequence of Bet v I. These 75 peptides were used to stimulate Bet v I-specific T cell clones. Our experiments revealed 7 distinct T cell epitopes on the Bet v I molecule. The epitopes were scattered over the whole molecule, 2 sequences were in agreement with an algorithm previously described for the prediction of T cell epitopes. In 3 cases, we could identify distinct TCC specificities within single individuals. Furthermore, for each donor, none of the peptides representing epitopes for TCC inhibited the binding of IgE antibodies to Bet v I. These results suggest that T cells and IgE antibodies from the same individual recognize different structures on the Bet v I allergen.
The fate of anergic T cells in vivo.
Authors: Migita K , Ochi A
Published: December 2022

The kinetics of Staphylococcal enterotoxin B-(SEB) induced peripheral tolerance has been investigated. Ten days after SEB injection, thymectomized BALB/cByJ mice showed suppressed spleen cell proliferative responses to SEB. After 2 mo the SEB-specific response was partly recovered. Four months later the response of spleen cells of SEB-primed mice was comparable to those of control mice. The proportion of CD4+, V beta 8+ T cells was diminished in the tolerized mice and was not restored even after the response was recovered. Purified CD4+, V beta 8+ T cells from SEB-primed mice after 4 mo responded similarly to SEB as control CD4+, V beta 8+ T cells. These expressed a similar profile of surface markers compared with that of unprimed control cells, except a homing receptor was slightly lower. An experiment that addressed the possibility that non-anergic T cells expand over time and are in fact responsible for the recovery of the proliferative response showed that such events unlikely occur in vivo. Therefore, the data indicate that T cell anergy is reversible in vivo. It is also suggested that the challenge with superantigen results in neither clonal expansion nor specific CD4+, V beta 8+ T cell memory.
Inducible T cell antigen 4-1BB. Analysis of expression and function.
Authors: Pollok K E , Kim Y J , Zhou Z , Hurtado J , Kim K K , Pickard R T , Kwon B S
Published: December 2022

4-1BB is an inducible receptor-like protein expressed in both cytolytic and Th cells. Optimal induction of 4-1BB mRNA in T cells required both PMA and ionomycin stimulation, indicating that protein kinase C activation and increases in intracellular Ca2+ were required for its expression. 4-1BB was categorized as an early activation gene since the protein synthesis inhibitor, cycloheximide, blocked the induction of 4-1BB mRNA. A rat mAb, 53A2, was generated against recombinant soluble 4-1BB and was used to characterize this molecule. 4-1BB is a 30-kDa glycoprotein and appears to exist as both a monomer and a 55-kDa dimer on the cell surface of a T cell clone. The 4-1BB protein may be post-translationally modified since its predicted backbone is 25 kDa. FACS analysis indicated that 4-1BB was inducible and expressed on the cell surface of activated splenic T cells and thymocytes. Cross-linking of 4-1BB on anti-CD3-stimulated T cells with 53A2 resulted in a dramatic enhancement of T cell proliferation. This suggests that 4-1BB may function as an accessory signaling molecule during T cell activation.
Lack of promiscuity in autoantigen-specific H and L chain combinations as revealed by human H and L chain "roulette".
Authors: Portolano S , Chazenbalk G D , Hutchison J S , McLachlan S M , Rapoport B
Published: December 2022

Individual H or L chains from a human autoantibody were used to search for other L or H chains that could form antigen-binding fragments, Fab, with the same specificity. The parent Fab (SP1.2) exhibits high affinity binding for thyroid peroxidase (TPO), a 107-kDa protein that is the major autoantigen in human autoimmune thyroiditis. This autoantibody "roulette," performed by using Ig H and L chain gene libraries expressed in bacteria, increased the frequency of TPO-binding clones in the new libraries. However, the frequency was still much lower than would be the case if promiscuous combinations with a variety of H or L chains were compatible with specific Ag binding. Nucleotide sequence analysis of the H and L chains of the new TPO-binding clones revealed even more restriction. Thus, with the SP1.2 H chain, all 11 new Fab utilized L chains from the same V kappa 1 family germline gene as SP1.2 itself. Similarly, five of six H chains "captured" by the SP1.2 L chain were very closely related to the SP1.2 H chain. However, one totally different H chain was isolated: SP4.6 has a VH region that differs substantially from that of SP1.2. SP4.6 also has a distinct D region, uses a different JH, and, unlike SP1.2, which is an IgG1, belongs to subclass IgG4. The affinities for TPO of SP4.6 (with the different H chain) and SP1.20 (which had the least mutated L chain germline gene) were similar to that of SP1.2 (approximately 10(-10) M). As expected, the SP1.2 and SP1.20 Fab, which have the same H chain and closely related L chains, bound to the same domain on TPO. However, a similar domain on TPO was recognized by both SP4.6 and SP1.2, despite the fact that their V, D, and J regions are quite different. This observation raises the possibility that the L chain is critical in defining epitope specificity, even in the presence of completely different D regions and nonidentical VH regions.
Schistosoma mansoni 28-kDa glutathione S-transferase and immunity against parasite fecundity and egg viability. Role of the amino- and carboxyl-terminal domains.
Authors: Xu C B , Verwaerde C , Gras-Masse H , Fontaine J , Bossus M , Trottein F , Wolowczuk I , Tartar A , Capron A
Published: December 2022

We have previously shown that a mAb that inhibits the enzymatic activity of the Schistosoma mansoni 28-kDa glutathione S-transferase (Sm28 GST) also reduces female worm fecundity and egg viability in vivo and in vitro. By peptidic epitope mapping and an activity reconstitution assay, the carboxyl terminus (CT) amino acid residues 190-211 and to a lesser extent the truncated amino terminus (NT) residues 10-43 of the enzyme were identified as mAb recognition sites. Sera from rats immunized with the NT (10-43) and CT (190-211) peptides showed a partial inhibitory effect on Sm28 GST activity in a late phase (6 to 7 wk) but not in an early phase (2 to 4 wk) after immunization. Passive transfer of Sm28 GST-inhibiting anti-N- and C-terminal sera, but not of the noninhibitory sera, protected the infected mice by reducing tissue egg deposition and the ability of eggs to hatch. In active immunization experiments, the CT peptide significantly decreased the worm burden (37 to 40%) in mice as did the rSm28 GST (28 to 52%). In terms of tissue egg deposition and egg-hatching ability, immunization with both the NT and CT peptides reproduced the reduction observed after immunization with rSm28 GST. A constant reduction in egg numbers was noted in the small intestines and the livers of the immunized mice. A clear reduction in the ability of intestinal or hepatic eggs to hatch was observed. The results are discussed in terms of the conformational participation of the NT and CT of Sm28 in the expression of GST activity.
A novel cytokine-responsive cell surface glycoprotein defines a subset of medullary thymic epithelium in situ.
Authors: Farr A , Nelson A , Hosier S , Kim A
Published: December 2022

A hamster mAb (10.1.1), raised against long term cultures of uncloned thymic stromal cells, selectively labeled a subpopulation of medullary stromal cells in situ. By ultrastructural and phenotypic criteria, the stromal cells labeled by this mAb were judged to be epithelial. Although some of the 10.1.1+ epithelial cells were reticular, others were globular and some were associated with structures resembling Hassal's bodies. Ultrastructural immunohistochemistry suggested that 10.1.1 labeling of some of the epithelial cells was preferentially associated at areas of epithelial cell contact with adjacent thymocytes. Reactivity of thymic stromal cells with this antibody was developmentally regulated. A few scattered 10.1.1+ cells were observed at day 14 of gestation, and there were progressive increases in both the extent and intensity of 10.1.1 labeling evident through birth. One thymic stromal cell line, Z210.1, exhibited low levels of constitutive reactivity with this antibody. Exposure to IL-1 resulted in enhanced 10.1.1 reactivity of this cell line, with little, if any, additional response to TNF-alpha or IFN-gamma. Under the same conditions, ICAM-1 expression by this cell line was elevated in response to IL-1, TNF-alpha, or INF-gamma. Immunoprecipitation of detergent lysates prepared from Z210.1.7 cells exposed to IL-1 24 h before cell surface iodination identified a cell surface protein with a molecular mass of about 92 kDa under nonreducing conditions and about 95 kDa under reducing conditions. Digestion of 10.1.1 immunoprecipitates with N-glyconase resulted in a small (5 kDa) reduction in molecular mass. The molecule recognized by the 10.1.1 mAb was distinct from ICAM-1, which possessed a molecular mass of 100 kDa (nonreduced) and 110 kDa (reduced), and also displayed a smaller N-glyconase-resistant molecular mass (65 to 85 kDa).
Immunoregulatory role of CD40 in human B cell differentiation.
Authors: Splawski J B , Fu S M , Lipsky P E
Published: December 2022

CD40 is a member of a family of surface molecules with homology to the nerve growth factor receptor and is expressed on B cells. The role of CD40 in regulating human B cell differentiation and the production of specific Ig isotypes was examined. In the absence of other stimuli, anti-CD40 and IL-4 induced the secretion of IgM, IgG, and IgE by purified human peripheral blood B cells. However, addition of formalinized Staphylococcus aureus (SA) enhanced the response. In the presence of SA, anti-CD40 and IL-4 induced the secretion of IgM, IgG1, IgG2, IgG3, and IgG4 in addition to IgE. No consistent effect on IgA secretion was demonstrated. The combination of SA, anti-CD40, and IL-4 induced one tenth of the total Ig production that was stimulated by SA and IL-2, with a different distribution of Ig H chain isotypes. B cells stimulated with SA, anti-CD40, and IL-4 secreted a greater percentage of IgG4 and IgE and a decreased percentage of IgG1 and IgA, compared with that secreted in response to SA and IL-2. Anti-CD40 did not induce Ig production in combination with IL-2 and did not alter the Ig secreted in response to SA and IL-2. Stimulation with SA, anti-CD40, and IL-4 caused Ig H chain isotype switch, inasmuch as IgG and IgE secretion could be induced from preimmune cord blood B cells and IgD+ naive adult B cells and IgE secretion could be induced from IgE- adult B cells. Ig secretion by purified B cells stimulated with SA, IL-4, and anti-CD40, but not with SA and IL-2, was significantly enhanced by anti-CD18 or anti-ICAM-1 mAb, suggesting that homotypic aggregation induced by anti-CD40 might limit Ig production. Finally, anti-CD40 was found to inhibit Ig production by B cells cultured with anti-CD3-activated T cells. These results suggest that engagement of the CD40 molecule on B cells provides signals that permit IL-4 to induce Ig isotype switching. This response is limited by LFA-1-mediated homotypic interactions of B cells. Engagement of CD40 by the ligand expressed by activated T cells appears to be important for the activation of B cells during T cell-B cell collaboration and the production of all isotypes of Ig.
Purified beta-chain of MHC class II binds to CD4 molecules on transfected HeLa cells.
Authors: Nag B , Wada H G , Passmore D , Clark B R , Sharma S D , McConnell H M
Published: December 2022

The initial event triggering the activation of Th cells occurs when the TCR interacts with antigenic peptide in the context of the MHC II on APC. Various T cell accessory molecules including CD4, CD28, and LFA-1 participate and facilitate the activation event. Although some evidence for the interaction of MHC II and CD4 is available, the site of MHC class II (alpha-chain, beta-chain, or both chains) for CD4 interaction has not yet been clearly defined. Results from different laboratories had indicated the involvement of alpha 1, beta 1, and beta 2 domains of MHC class II molecules in CD4 interaction. Recently, a conserved site of DR beta 2 domain has been identified that involves CD4 interaction that is analogous to MHC class I binding site for CD8 molecule. In this report, direct binding of affinity-purified HLA-DR2 dimer and its isolated alpha- and beta-chains to CD4 was studied using a CD4-transfected HeLa cell line. Preferential binding of the beta-chain and intact MHC II dimer to the CD4-transfected cells was observed and found to be specifically inhibited by anti-CD4 mAb. In contrast, the isolated alpha-chain of HLA DR2 did not show significant binding to CD4-transfected cells. Complexes of radiolabeled DR2 dimer or beta-chain alone with an immunodominant epitope from myelin basic protein (83-102) did not show any further increase in binding of these molecules. Binding of the beta-chain to CD4+ cells was markedly inhibited by a DR beta 1 peptide (35-46) and was partially inhibited by a DR beta 2 peptide (134-148) of MHC class II molecule. These results suggest the involvement of at least two conserved regions of the beta polypeptide chain of MHC class II in CD4 interaction. Because in our experiments transfected cells lack TCR molecules and the binding of DR2 to the CD4-transfected cells was unaffected by added antigenic peptide, it is possible that the interaction of MHC class II to CD4 is independent of TCR occupancy.
V region diversity in human anti-insulin antibodies. Preferential use of a VHIII gene subset.
Authors: Thomas J W
Published: December 2022

Data on structures used by human antibody repertoires are derived principally from lymphoid malignancies and from autoantibodies that often express VH genes from the developmentally regulated fetal repertoire. To determine whether human immune responses generated by exogenous Ag use a pool of VH genes distinct from the fetal repertoire, nucleotide and predicted amino acid sequences were determined for five anti-insulin B cell clones from a type I diabetic patient treated with human insulin. The data show that a set of VHIII genes is preferentially used by human anti-insulin B cells. Structural features indicate that these expressed VH are derived from germ-line genes that are not frequent in fetal repertoires and these genes have undergone Ag-driven somatic mutation. The preferential use of related VH segments contrasts with the BALB/c anti-insulin response, which uses multiple V genes elements largely unmutated from germ-line sequences. In addition, long CDRH3 structures in human anti-insulin mAb are generated by complex gene interaction mechanisms that are not seen in murine anti-insulin mAb. Interestingly, similar potential insulin-binding structures are used by antibodies from both species. These findings suggest that human responses to exogenous insulin may express a limited number of VH genes and depend upon somatic mutation and complex D gene interactions in CDRH3 to expand the repertoire. Although these antibodies bind autologous insulin, VH gene usage and structural features that predominate in the response are not characteristic of the fetal repertoire.
MHC class I expression on tumor targets inhibits natural killer cell-mediated cytotoxicity without interfering with target recognition.
Authors: Kaufman D S , Schoon R A , Leibson P J
Published: December 2022

NK cell-mediated killing is inversely proportional to the amount of MHC class I expression on certain tumor targets. Two hypotheses have been proposed to explain why class I-bearing targets are more resistant to NK cell-mediated lysis: 1) the presence of class I prevents NK cell recognition of a triggering molecule on the target cell surface, or 2) class I recognition transmits a separate inhibitory signal to the NK cell. To differentiate between these potential mechanisms, we have used cloned human CD16+/CD3- NK cells, the class I-deficient cell line C1R, and C1R cells expressing high levels of transfected HLA class I gene products. If class I expression blocks NK cell recognition of the targets, then proximal cell signaling events such as phospholipase C-mediated hydrolysis of membrane phosphoinositides should be decreased in the NK cells interacting with the class I transfectants. However, we found that increases in the level of target cell class I expressions did not decrease phosphoinositide turnover or calcium signaling in NK cells. We also examined the effect of treating HLA-transfected C1R cells with mAb specific for the transfected MHC class I gene product. If class I expression has a negative regulatory influence on NK cell activation, then treating the targets with anti-HLA mAb should block the transmission of this negative signal. Consistent with this notion, addition of anti-HLA mAb (either whole Ig or F(ab')2 fragments) led to increased lysis of the class I-transfected targets. In contrast, addition of isotype-matched mAb specific for other cell surface markers did not alter sensitivity to lysis. All of these results suggest that MHC class I expression on target cells can initiate inhibitory signals in NK cells without blocking access to target structures.
Catecholamines stimulate MHC class I, class II, and invariant chain gene expression in brain endothelium through different mechanisms.
Authors: Bourdoulous S , Durieu-Trautmann O , Strosberg A D , Couraud P O
Published: December 2022

Bovine brain microvessel endothelial cells in primary culture retain a differentiated phenotype reminiscent of the in vivo blood-brain barrier endothelium. The IFN-gamma-induced surface expression of MHC class II molecules on those cells is stimulated by catecholamines through a cAMP-independent mechanism. We report that both the induction of MHC class II molecule expression by IFN-gamma and its potentiation by isoproterenol, a catecholamine analog, are preceded by increases of steady-state levels of the corresponding mRNA. Similar results were obtained for the regulation of invariant chain expression. In addition, isoproterenol alone is able to increase class I mRNA levels, but, in contrast to what is observed for class II expression, this effect appears to be mainly mediated by cAMP. These studies demonstrate that, in bovine brain microvessel endothelial cells, catecholamines up-regulate MHC class I and class II Ag, as well as invariant chain with different kinetics and through different mechanisms and suggest that these regulatory effects occur at the transcriptional level.
In vitro production of IL-6, IL-1 beta, and tumor necrosis factor-alpha by human embryonic microglial and neural cells.
Authors: Sébire G , Emilie D , Wallon C , Héry C , Devergne O , Delfraissy J F , Galanaud P , Tardieu M
Published: December 2022

The abilities of the different cells from human central nervous system (CNS) to produce IL-6, IL-1 beta, and TNF-alpha were tested in vitro using either cultures enriched in human embryonic microglial cells or primary cultures of human embryonic CNS cells. High amounts of IL-6, low amounts of IL-1 beta but no TNF-alpha were detected in supernatants of microglial cells, kept either in FCS-free conditions or in FCS-containing medium. Moreover, IL-6 mRNA was also present in 45 to 55% of microglial cells cultured in the presence of FCS as visualized by in situ hybridization, whereas IL-1 beta mRNA remained undetectable. After prestimulation of microglial cells with LPS or IL-1 alpha, the percentage of cells labeled with an antisense IL-6 mRNA probe increased to 70% and hybridization with an antisense IL-1 beta mRNA probe became detectable. In contrast to this dyscoordinate production of cytokines by microglial cells, human monocytes, freshly isolated from blood and kept in the same culture conditions, produced high levels of the three cytokines tested. In primary cultures of human embryonic CNS cells, IL-6, IL-1 beta, and TNF-alpha were produced mostly or only by microglial cells because no IL-1 beta mRNA or IL-6 mRNA were detected in astrocytes, even after prestimulation with LPS or IL-1 alpha. Finally, IL-1 was the main inducer of IL-6 production because IL-1 alpha, but not LPS, induced a significant increase in IL-6 synthesis in cultures kept in FCS-free medium. However, in presence of FCS, LPS appeared to initiate a cascade reaction involving the production of IL-1 by microglial cells, acting as an autocrine loop to trigger IL-6 synthesis.
Anti-CD3:anti-IL-2 receptor bispecific monoclonal antibody. Targeting of activated T cells in vitro.
Authors: MacLean J A , Su Z , Guo Y , Sy M S , Colvin R B , Wong J T
Published: December 2022

T cells are major mediators of graft rejection and many autoimmune diseases. During the Ag recognition process, T cells often become activated. We tested the hypothesis that an anti-CD3:anti-CD25 (CD3,25) bispecific mAb (BSMAB) can effectively and selectively target activated T cells. By flow cytometric analysis, the CD3,25 BSMAB was shown to bind avidly to activated T cells that coexpress CD3 and CD25 (p55 chain of the IL-2R), achieving higher levels than the parent anti-CD3 and anti-CD25 mAb. It bound only weakly to unstimulated T cells. The CD3,25 BSMAB effectively redirected CTL to lyse CD25-bearing PHA-stimulated T lymphoblasts and the IL2-dependent CTLL tumor cell line in chromium release assays. It was highly effective in blocking MLR as shown by inhibition of [3H]TdR incorporation. However, the CD3,25 BSMAB has a low potential to activate resting T cells, as it induced only minimal [3H]TdR incorporation even in the presence of exogenous IL-2. In the absence of exogenous IL-2, the CD3,25 BSMAB was unable to induce [3H]TdR incorporation. In contrast, the parent anti-CD3 mAb induced a high degree of incorporation. In summary, the CD3,25 BSMAB selectively targets activated CD25-expressing T cells and lymphomas although maintaining a low activation potential for unstimulated T cells, potentially advantageous properties that can be exploited for immunotherapy.
Regulation of protein kinase C isoform proteins in phorbol ester-stimulated Jurkat T lymphoma cells.
Authors: Tsutsumi A , Kubo M , Fujii H , Freire-Moar J , Turck C W , Ransom J T
Published: December 2022

Activation of protein kinase C (PKC) in T cells leads to a variety of responses including IL-2 production and IL-2 receptor expression. PKC consists of several isoforms that exhibit some different in vitro properties. We have set up a Western blotting system to explore the regulation of PKC isoforms during T cell activation. In Jurkat T lymphoma cells, PKC alpha, beta, delta, epsilon, and zeta were detected. PKC alpha and beta existed primarily in the cytosol, translocated to the membrane fraction after 10 minutes of treatment with PMA, and almost completely disappeared within 16 h. A larger fraction of PKC delta and epsilon existed in the membrane fraction compared to PKC alpha or beta, and PKC epsilon translocated to the membrane fraction rapidly. Translocation of PKC delta was not apparent after 1 h treatment with PMA, but total PKC delta protein was reduced within 4 to 6 h of treatment. Consistent with this, overnight treatment with PMA caused down-regulation of both PKC delta and epsilon, but to a lesser degree than was observed with PKC beta. Anti-PKC zeta antibody detected two bands at 82 and 75 kDa. The 75-kDa band existed mostly in the cytosol fraction and showed no translocation or down regulation after PMA. We present evidence that this 75-kDa band represents PKC zeta. Similar PMA-induced translocation responses were observed in murine thymocytes showing that the responses are not unique to PKC isoforms in Jurkat. These results demonstrate that it is possible for the PKC isoforms to be differentially regulated during T cell activation.
Direct demonstration of membrane IL-1 alpha on the surface of circulating B lymphocytes and monocytes.
Authors: Zola H , Flego L , Wong Y T , Macardle P J , Kenney J S
Published: December 2022

A mAb against IL-1 alpha has been used in a high sensitivity immunofluorescence procedure to demonstrate directly the presence of surface IL-1 alpha on human monocytes and B cells from blood and tonsil. IL-1 alpha could be detected on monocytes and a subset (around 30%) of B cells without any in vitro activation. Although the subset of B cells expressing IL-1 alpha was distinct (i.e., the distribution of fluorescence intensity was bimodal), no correlation was seen with any other B cell subset marker in blood. In tonsil, IL-1 alpha was expressed by cells with a phenotype that suggested that they represented a subset of mantle zone B cells. Activation of tonsil B cells with anti-IgM, IL-4, IL-2, and mixtures of these reagents led to small increases in IL-1 alpha expression, as did activation of unfractionated tonsil cells with PHA.
Production of transforming growth factor-beta by Mycobacterium avium-infected human macrophages is associated with unresponsiveness to IFN-gamma.
Authors: Bermudez L E
Published: December 2022

Transforming growth factor-beta 1 (TGF-beta 1) is a potent immunoregulatory molecule. It modulates production of cytokines, such as TNF-alpha and IL-6, and cell response to cytokine stimulation. Mycobacterium avium is an intracellular bacterium that multiplies within macrophages. The reason why M. avium can survive within macrophages is still unknown but probably is multifactorial. Exposure of M. avium-infected macrophages to rTGF-beta 1 before TNF stimulation significantly decreases the mycobactericidal/mycobacteriostatic activity associated with treatment with TNF. Infection of human monocyte-derived macrophages in vitro with M. avium strains belonging to serovars 1, 4, and 8 induced secretion of biologically active TGF-beta. The production of TGF-beta was strain dependent and was more pronounced in macrophages infected with virulent strains. Incubation of macrophages with M. avium-derived 33-kDa and 65-kDa proteins was associated with significant release of biologically active TGF-beta. Treatment of M. avium-infected macrophages with rTNF-alpha in the presence of anti-TGF-beta 1 antibody induced significantly greater killing of M. avium than did treatment of macrophages with TNF-alpha in the absence of anti-TGF-beta 1 antibody. In addition, macrophage monolayers treated with anti-TGF-beta 1 antibody before infection with M. avium showed mycobactericidal activity after stimulation with rIFN-gamma; in contrast, no effect of IFN-gamma was seen in monolayers not treated with anti-TGF-beta 1 antibody. We conclude that TGF-beta 1 produced after M. avium infection is a potent inhibitor of macrophage activation by cytokines. This inhibition may have an important role in the regulation of the immune response against M. avium.
Human peripheral gamma delta T cells recognize hsp60 molecules on Daudi Burkitt's lymphoma cells.
Authors: Kaur I , Voss S D , Gupta R S , Schell K , Fisch P , Sondel P M
Published: December 2022

Studies with the use of polyclonal rabbit antiserum reactive with 60-kDa heat shock proteins (hsp60) suggested that hsp60-related molecules could be found on the surface of Daudi cells and were involved in their recognition by certain human gamma delta T cells. The present study confirms this finding by using a mAb specifically recognizing hsp60. This mAb can block outgrowth of human gamma delta T cells in response to stimulation with Daudi and in response to an extract of the mycobacteria H37Ra. This anti-hsp60 mAb stains the surface of Daudi cells, but does not stain either Raji or EBV-transformed B cells, cells which do not stimulate gamma delta T cell outgrowth. Anti-hsp60 mAb could immunoprecipitate a 60-kDa molecule from the H37Ra extract but was unable to precipitate this 60-kDa molecule if the mAb was first absorbed on Daudi cells. This mAb also precipitated a 60-kDa molecule from the surface of Daudi cells which shows an electrophoretic mobility pattern consistent with hsp60. These experiments demonstrate that human gamma delta T cells recognize hsp60-related epitopes on the surface of Daudi cells and within mycobacterial extracts.