bluuebunny/crossref_metadata_2025_split huggingface dataset:
A model system for the study of the assembly and regulation of human complement C3 convertase (classical pathway)
Authors: Thielens Nicole M. , Colomb Maurice G. 
Published: February 2007

AbstractThe formation of classical C3 convertase of complement and its regulation by C4b‐binding protein (C4bp) were studied using two different approaches: (a) the analysis was first carried out in fluid phase; a soluble stabilized C3 proconvertase could be assembled from C4b (or C4b‐like C4) and iodine‐treated C2 in the presence of Ni2+ ions. Upon activation of this complex by C1s, a C3 convertase C4b(C4b‐like C4)‐C2a was generated which was able to cleave purified C3. C4bp dissociated both C3 proconvertase and C3 convertase, but its effect was more important on C3 convertase. (b) A model system of phospholipid vesicles has been developed to study the assembly of the C3 convertase on a membrane. Among different phospholipid mixtures tested, P‐glycerol/P‐choline vesicles were found most effective for C4b binding. Optimal conditions were determined for C4b fixation on these vesicles; bound C4b participated in the formation of a functional membrane‐associated C3 convertase. C4bp was found to bind to phospholipid vesicles with a higher affinity than C4b; it was able to dissociate the vesicle‐associated C3 convertase.
Hapten‐specific cytotoxic T cell clones undergo somatic variation of their antigen recognition specificity
Authors: Weltzien Hans Ulrich , Kempkes Bettina , Jankovic Dragana L. , Eichmann Klaus 
Published: February 2007

AbstractTwo experimental systems have demonstrated somatic variation of antigen recognition specificity of long‐term cytotoxic T cell (CTL) clones. System 1 used CTL clone BT7.4.1 with strict specificity for Kb/TNP, which had been continuously cultured for 15 months in the presence of H‐2b/TNP stimulator cells and interleukin 2. Upon removal of the TNP antigen from the cultures, 99% of the clone cells within about 10 cell divisions lost their ability to grow in the presence of antigen and interleukin 2 (lethal variants). Of the surviving 1%, about 60% retained the ability to lyse target cells in the presence of lectins but only 12% could be considered as “wild type” BT7.4.1 cells, i.e. they still specifically lysed H‐2b/TNP‐bearing target cells. The majority of the growing cells, thus, had to be considered as specificity loss variants. Several specificity loss variants were established in culture and were shown to express membrane‐bound T cell “receptor” heterodimer similar to their TNP‐specific ancester, BT7.4.1. Principally the same types of variants were generated in cultures growing in the presence of TNP antigen, although in quantitatively reduced numbers. Under these conditions the specific stimulator cells appeared to impose a significant selective advantage for “wild type” CTL since even after 15 months the cultures fully retained their specificity for the nominal antigen.In system 2, the development of cytolytic fine specificity of a panel of 42 individual Kb/TNP‐specific CTL clones was followed over a period of 8 months of in vitro culture. At the beginning of the test, 37 of these clones exhibited significant cross‐reactivity for lysis of H‐2k/TNP target cells. This number of cross‐reactive clones continuously diminished with time and dropped to only 4 clones after 8 months in culture. All 42 clones retained their original Kb/TNP specificity and after losing their reactivity for H‐2k/TNP usually showed no decrease but rather an increase in their cytotoxic activity towards Kb/TNP target cells. Loss of H‐2k/TNP cross‐reactivity was not accompanied by loss of Lyt‐2 or of LFA‐1 surface antigens or by loss of sensitivity of the cytotoxicity to inhibition by anti‐Lyt‐2 or by anti‐LFA‐1 antibody.We conclude from these observations that in vitro cultivated CTL clones, at least those of C57BL/6 anti‐TNP‐C57BL/6 specificity, are not stable in terms of their antigen recognition specificity. Despite this instability, their nominal cytolytic specificity can be maintained over long periods of in vitro culture and even a maturation to increased antigen specificity is regularly observed, provided antigen is present in the cultures. We assume this indicates that maintenance of clonal specificity in vitro is a matter of antigen‐induced selection rather than a consequence of structural stability of the antigen receptor.
Evidence for a T suppressor cell‐inducing antigenic determinant shared by ADJ‐PC‐5 plasmacytoma and syngeneic BALB/c spleen cells
Authors: Kloke Otto , Haubeck Hans‐Dieter , Kölsch Eckehart 
Published: February 2007

AbstractThe BALB/c plasmacytoma ADJ‐PC‐5 induces in early stages of tumorigenesis specific T suppressor (Ts) cells apparently as the first reaction of the immune system towards the growing tumor. In attempts to apply the concept of early induction of Ts cells in neoplasia for the induction of tolerance to allografts we have tried to induce Ts cells against alloantigens by injecting allogeneic spleen cells in doses increasing exponentially from 10 to 105 cells/mouse. Experiments using various strain combinations failed to demonstrate induction of specific Ts cells by this procedure. To explain the apparent discrepancy between these and the tumor data the capacity of the ADJ‐PC‐5 tumor cells to induce Ts cells in allogeneic combinations was analyzed. ADJ‐PC‐5 cells are capable of inducing specific Ts cells in CBA/J mice. These Ts cells specifically suppress the induction of a primary cytotoxic T cell response of CBA/J spleen cells against BALB/c, BALB.B and (BALB/c × C57BL/6)Fl cells but not one against B10.D2 or C57BL/10 target cells. The ADJ‐PC‐5‐induced CBA/J Ts cells have been further analyzed using a panel of different target or responder cells. From these experiments the following conclusions can be drawn: the CBA/J Ts cells are specific for an antigen which is shared by ADJ‐PC‐5 and normal BALB/c spleen cells. The antigen in question is not coded for by the H‐2d major histocompatibility complex. The data suggest that the Ts cell‐inducing antigen on ADJ‐PC‐5 tumor cells is not a tumor associated neoantigen but a self antigen also present on normal BALB/c lymphoid cells.
Antigen presentation by liposomes: Inhibition with antibodies
Authors: Walden Peter , Nagy Zoltan A. , Klein Jan 
Published: February 2007

AbstractThe involvement of both antigen and class II major histocompatibility complex (MHC) molecules in T cell activation by liposome‐bound antigens was investigated. We used a pigeon cytochrome c (PCC)‐specific Ek‐restricted T cell hybridoma that can be activated to produce interleukin 2 by liposomes carrying either PCC and Ek molecules, or a high concentration of PCC alone. We demonstrated that the MHC‐restricted response of this hybridoma to liposomes is specifically blocked by both anti‐MHC and anti‐PCC monoclonal antibodies, whereas unrestricted activation is only inhibited by PCC‐specific antibody.
Inhibition and enhancement of in vitro helper activity of apocytochrome c‐specific murine T cell populations and clones by anti‐apocytochrome c‐specific monoclonal antibodies
Authors: Titus Richard G. , Corradin Giampietro 
Published: February 2007

AbstractA murine monoclonal antibody (mAb) specific for apocytochrome c was found to be able to either inhibit or enhance the helper activity of mouse apocytochrome c‐ specific T cell clones and populations in a hapten (trinitropheny1)‐carrier (apocytochrome c) system of T‐B cell cooperation. This effect of the mAb was carrier specific, could not be ascribed simply to a shift in the kinetics of the antibody response and was observed using apocytochrome c T helper cells of different mouse haplotypes. In addition, the anti‐apocytochrome c mAb was able to inhibit specific T helper cell activity even when the T cells were triggered with antigen‐presenting cells pulsed with antigen. Taken together, these results suggested that the mAb was inhibiting helper activity due to its ability to modify the interaction between T cells and antigen‐ presenting cells.
Interferon‐α/β enhances the expression of Ly‐6 antigens on T cells in vivo and in vitro
Authors: Dumont Francis J. , Coker Lisa Z. 
Published: February 2007

AbstractInterferons (IFN) have been shown to modulate the expression of a number of cell surface antigens on macrophages and lymphocytes. Because such phenotypic alterations may be involved in the functional effects of IFN, it appears important to characterize further these alterations. In the present work, we evaluated the response to IFN of Ly‐6‐encoded molecules on murine T cells. Two types of Ly‐6 antigens, Ly‐6A and Ly‐6C, normally present on minor subsets of mature T cells were studied. It was found that in vivo treatment of mice with the IFN inducer poly(I.C) or with purified IFN‐α/β resulted two days later in augmented expression of these antigens. Purified T cells cultured in vitro for 2 days in the presence of 5% serum from poly(I.C)‐treated mice or of lo4 units/ml IFN‐α/β also displayed dramatically increased (4‐12‐fold) amounts of Ly‐6 antigens. Under the same conditions, the T cell markers Thy‐1, Ly‐1, Lyt‐2 and MT4 were unaffected or slightly diminished while surface expression of H‐2 or β2‐microglobulin antigens was increased by only 10‐36%. Therefore, poly(1. C)‐ induced or purified IFN interacts with resting T cells to selectively enhance Ly‐6 antigen expression. This phenomenon was found to correlate functionally with increased proliferative response of the T cells, in presence of phorbol myristate acetate, to anti‐Ly‐6 antibodies cross‐linked on their surface. Enhancement of Ly‐6 antigen expression on T cells may thus play a role in IFN‐mediated immunoregulation.
B cell growth and differentiation factors interact with receptors distinct from the interleukin 2 receptor
Authors: Kehrl John H. , Grove Julia H. , Goldsmith Paul K. , Fauci Anthony S. 
Published: February 2007

AbstractHuman B lymphocytes preactivated with Staphylococcus aureus Cowan strain I can proliferate and differentiate to Ig‐secreting cells when cultured in the presence of recombinant interleukin 2 (IL2). We have compared 2 different B cell growth factors (BCGF) and a B cell differentiation factor (BCDF) to IL2 in the regulation of human B lymphocyte growth and differentiation. Utilizing a competitive binding assay, neither a high molecular weight BCGF (HMW‐BCGF) nor a low molecular weight BCGF (LMW‐BCGF) competitively inhibited the binding of radiolabeled IL2. Blocking studies with the anti‐Tac monoclonal antibody demonstrated that B cell proliferation to IL2 was inhibited while a crude supernatant containing BCGF and IL2 was only partially inhibited. B cell Ig secretion induced by IL2 was also inhibited by anti‐Tac while a crude supernatant and partially purified BCDF were not. Furthermore, IL2 plus BCGF was shown to enhance B cell proliferation better than either factor alone and IL2 plus a BCDF enhanced B cell Ig secretion better than either factor alone. By separating activated B cells into Tac‐positive and Tac‐negative fractions, much of the previously noted enhancement with the 2 factors was found to be secondary to the differential sensitivity of the 2 populations to BCGF and IL2 or BCDF and IL2. Thus, LMW‐BCGF, HMW‐BCGF and a partially purified BCDF appear to interact with receptors distinct from the IL2 receptor in mediating their effects on B cell growth and differentiation.
Suicide selection of murine T helper clones specific for variable regions of the influenza hemagglutinin molecule
Authors: Brian Thomas D. , Skehel John J. , Mills Kingston H. G. , Graham Christine M. 
Published: February 2007

AbstractA negative selection procedure has been developed to obtain murine T helper clones specific for variable regions of the influenza A hemagglutinin. T cell lines, established from mice primed by intranasal infection with X31 (H3N2) virus, were cross‐stimulated with natural variant viruses of known primary sequence (either A/TEXAS/1/77 or A/ENG878/69) and proliferating cells eliminated by treatment with the cell cycle‐ specific drug 5‐bromodeoxyuridine. After two suicide cycles, T cell lines were subtype specific and failed to recognize the natural variants. Clones were established by limiting dilution and their specificity was determined against a panel of viruses. Extensive diversity was evident in the reactivity of clones from individual donors, and two major T cell recognition sites were defined in the globular head region of the hemagglutinin molecule.
IgE receptors on human lymphocytes I. Identification of the molecules binding to monoclonal anti‐Fcε receptor antibodies
Authors: Nakajima Toshiharu , Delespesse Guy 
Published: February 2007

AbstractThe present study indicates that the surface molecules from Fcε receptor‐bearing human lymphoblastoid cells binding to monoclonal antibodies to Fcε receptor (mAbER) are identical to those binding to IgE. mAbER identify three components in the Nonidet‐P40 cell lysate of surface‐iodinated RPMI 8866 cells with approximately 65–95 kDa, 45 kDa and 37 kDa as estimated by sodium dodecyl sulfate‐polyacryl‐amide gel electrophoresis under reducing conditions and autoradiography. The same pattern is observed under nonreducing conditions, except for the low mol. wt component which displays an apparent molecular mass 31 kDa. When the labeled and solubilized membranes are adsorbed on IgE‐Sepharose the 45‐kDa component is always found in the eluate, whereas the 65–95‐kDa component is occasionally detected and the low mol. wt component is rarely found. The binding of these molecules to IgE‐Sepharose is inhibited by soluble IgE, mAbER but not by an unrelated mAb; reciprocally, the binding to mAbER‐Sepharose is prevented by mAbER and to some extent by IgE. To improve the stability of IgE‐FcεR complexes, biotinylated IgE was cross‐linked on surface iodinated intact cells, which were then solubilized and adsorbed on avidin‐Sepharose. Under these conditions, it was clearly shown that IgE binds to the same three surface molecules as mAbER. The isoelectric point of the high mol. wt component ranged from 4.2 to 4.4 as compared to 5.1–5.2 for the 45‐kDa and the 37‐kDa components. The observation in the Western blot assay that both the 65–95‐kDa and the 45‐kDa molecules react with 9 different mAbER indicates that these molecules have a polypeptide sequence in common.
IgE receptors on human lymphocytes II. Detection of cells bearing IgE receptors in unstimulated mononuclear cells by means of a monoclonal antibody
Authors: Delespesse Guy , Sarfati Marie , Rubio‐Trujillo Manuel , Wolowiec Terry 
Published: February 2007

AbstractA monoclonal antibody (mAb) specific for lymphocyte IgE receptors (ER) was employed in a rosette assay for the detection of cells bearing IgE receptors (FcεR). The specificity of the assay was documented by inhibition studies with soluble immunoglobulins (Ig) and anti‐Ig antibodies. Moreover, similar results were obtained by employing the F(ab')2 fragment of mAbER instead of intact molecule. Circulating mononuclear cells isolated from normal or allergic adults and from umbilical cord blood contained approximately 8% of FcεR‐bearing cells with values ranging from 0.3 to 17%. Tonsillar lymphocytes contained about 30% of FcεR+ cells. After the removal of adherent cells, there was a small but significant reduction of the proportion of FcεR+ cells. When mononuclear cells were separated into T and B cell fractions by two‐cycle rosetting with 2‐aminoethylisothiouronium bromide hydrobromide‐treated sheep red blood cells, most of the FcεR+ cells were in the B cell fraction; however, a small proportion of FcεR+ was also found in the enriched T cells and double‐labeling experiments confirmed that these cells were indeed T lymphocytes. FcεR+ cells were purified by rosetting with mAbER‐coated erythrocytes and their phenotype was compared to that of FcεR− cells; FcεR+ cells contained about 90% of B cells (B1+) together with a small proportion of OKT3+, Leu 7+ and Mo2+cells. The bulk of T cells, macrophages and natural killer (NK) cells was found in the FcεR− cells which contained fewer B cells than the fraction of FcεR+ cells. These data thus indicated that the great majority of FcεR‐bearing cells are B cells but that a small proportion of NK cells, macrophages and T lymphocytes also express FcεR. Upon incubation at 37°C, B cells lost their FcεR and this phenomenon was selectively inhibited by IgE; however, purified T cells seemed to express more FcεR after overnight incubation at 37°C and this was not influenced by IgE. It is finally shown that the expression of FcεR is cyclic and that FcεR‐bearing B cells do not represent a functionally distinct subpopulation of B lymphocytes.
Monoclonal antibodies against idiotypic determinant(s) of the T cell receptor from HPB‐ALL cells induce IL 2 production in Jurkat cells without apparent evidence of binding
Authors: Carrel Stefan , Giuffrè Laura , Vacca Angelo , Salvi Suzanne , Mach Jean‐Pierre , Isler Patrick 
Published: February 2007

AbstractTwo monoclonal antibodies (mAb) directed against idiotypic determinants of the T cell receptor (anti‐Ti) from HPB‐ALL cells induce interleukin 2 (IL2) production in Jurkat T cells without evidence of binding to these cells as judged by fluorescence‐activated cell sorter (FACS) analysis, indirect antibody‐binding radioimmunoassay and direct binding studies with 125I‐labeled mAb. The IL2 response induced by these mAb observed both in the presence and absence of phorbol myristate acetate was in the range of that obtained when Jurkat cells were stimulated with phytohemagglutinin or anti‐T3 mAb (Leu 4).The idiotypic specificity of the two anti‐HPB‐ALL Ti mAb was demonstrated by several criteria. Both mAb bound specifically to HPB‐ALL cells as determined by radioimmunoassay or FACS analysis but not with 8 other T cell lines. The anti‐HPB‐ALL Ti mAb precipitated a disulfide‐linked heterodimer of 85 kDa only from 125I‐labeled HPB‐ALL cells and not from other cell lines tested. Incubation of HPB‐ALL cells with anti‐T3 abrogated the expression of T3 and induced co‐modulation of the idiotypic structures detected by the two anti‐HPB‐ALL Ti mAb. Conversely, incubation of HPB‐ALL cells with either one of the anti‐Ti mAb abrogated the expression of T3 and of the idiotypic structures.Our results suggest that mAb with an apparent unique specificity for the receptor of the immunizing T cell line HPB‐ALL can activate Jurkat cells by a very weak cross‐reaction with these cells, which is not detectable by conventional binding tests.
Antigen‐induced changes in B cell subsets in lymph nodes: analysis by dual fluorescence flow cytofluorometry
Authors: Kraal Georg , Hardy Richard R. , Gallatin William M. , Weissman Irving L. , Butcher Eugene C. 
Published: February 2007

AbstractChanges in the representation and surface phenotype of defined B cell subsets in murine lymph nodes stimulated with keyhole limpet hemocyanin or sheep red blood cells have been analyzed by two‐color immunofluorescence fluorocytometric analysis. Shortly after immunization with either antigen there is a dramatic increase in both the frequency and absolute number of IgM+, IgD+ B cells, which is followed by the formation of germinal centers. Germinal center cells, as soon as they appear on day 3 after primary immunization, bind high levels of peanut agglutinin, bear low levels of surface IgM but no detectable surface IgD, and are characterized by lack of staining with MEL‐14, a monoclonal antibody which recognizes a lymphocyte surface receptor involved in lymphocyte homing. The level of I‐A and H‐2K region‐encoded surface antigens on early germinal center cells is higher than on PNAlo B cells. During the first 7 days of the germinal centers there is a progressive decrease in the average level of H‐2K but not of Ia antigens. A similar decrease was observed for ThB. It is confirmed that the germinal center cell population contains the majority of antigen‐binding cells in the stimulated lymph node. These findings indicate that B cells are recruited nonspecifically to antigen‐stimulated lymph nodes, and that the antigen‐specific cells then selectively participate in the formation of germinal centers where they undergo specific differentiation events.
The T lymphocyte response to syngeneic λ2 light chain idiotopes. Significance of individual amino acids revealed by variant λ2 chains and idiotope‐mimicking chemically synthesized peptides
Authors: Hannestad Kristian , Kristoffersen Gunn , Briand Jean Paul 
Published: February 2007

AbstractIn the present study we have investigated the structure of the helper T cell (Th)‐defined idiotope (Id) of myeloma protein 315 λ2 light chain (λ2315) in BALB/c (H‐2d) mice which carry a high‐responder immune response gene for this Id. Three eptides were synthesized which spanned the third hypervariable region (HV3) of λ2315: peptides 88–99, 94–108 and 91–108. Only peptide 91–108 was capable of eliciting carrier‐specific Th that recognized M315 or free λ2315. These Th did not recognize λ25–7 chain which differs from λ2315 at 4 positions in this region; these are Tyr94, Ser95, Thr96, Tyr98 for λ25–7 and Phe94, Arg95, Asn96, Phe98 for λ2315. Immunization with peptide analogues revealed that substitution of Tyr for Phe94 was compatible with Id‐λ2315 mimicry, but substitution of Ser for Arg95 or Thr for Asn96 destroyed the Th‐recognized Id. Furthermore, Th primed with λ25–7 chain did not cross‐react with λ2T952 these λ2 chains only differ from each other at positions 98 and 99 at the Vλ2‐Jλ2 junction. The data indicate that individual amino acids of short peptide segments are critical for Th‐recognized Id of the λ2 HV3 loop and Vλ2‐Jλ2 junction. Furthermore, the immunogenicity of a small peptide suggests that the carrier (λ2)‐specific Th recognize Id that have been processed by antigen‐presenting cells (APC). This implies the existence of two categories of “internal images” of foreign or of self antigens: (a) serologically defined and (b) T lymphocyte defined. We propose that as a rule, Id processing by APC, including B cells, destroys the first and reveals the second category. The possible physiological function of these Id‐specific T cells in network interactions with B cells is discussed.
Immunity to lymphocytic choriomeningitis virus in B cell‐depleted mice: evidence for B cell and antibody‐independent protection by memory T cells
Authors: Cerny Andreas , Huegin Ambros W. , Sutter Stefan , Bazin Hervié , Hengartner Hans H. , Zinkernagel Rolf M. 
Published: February 2007

AbstractImmunity against lymphocytic choriomeningitis virus (LCMV) in anti‐IgM‐treated B cell‐depleted mice was evaluated. We found that the following immune phenomena were independent of antibodies: (a) the generation of virus‐specific cytotoxic T cells; (b) the footpad swelling response against locally injected LCMV; (c) natural killer cell activity basic levels or after LCMV or poly(1). poly(C) stimulation; (d) immunopathologically mediated LCM after primary intracerebral inoculation; (e) immunological memory in LCMV‐immune mice assessed by immune protection against LCM after intracerebrally injected virus or as resistance against the local footpad swelling response to LCMV. This study demonstrates that humoral immunity plays no crucial role in immune protection and immunopathology in murine LCMV infection and suggests that protective memory T cell function is B cell and antibody independent.