摘要:

AbstractPurified terminal components of the complement system were used together with purified S‐protein, the inhibitor of the membrane attack complex, to generate the soluble complexes SC5b‐7, SC5b‐8 and SC5b‐9. These complexes were purified by ultracentrifugation in sucrose density gradients with 50–70% yield, exhibiting sedimentation coefficients of 20 S, 21 S and 23 S, respectively. In Ouchterlony double‐diffusion analysis, the purified complexes gave a line of identity against all antisera of the precursor components indicating that complex formation had occurred. The identity of the complexes was also revealed by the appearance of all subunit components after polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Since the inhibitor function of S‐protein in the terminal complement cascade should also be manifested in the morphology of the macromolecules generated, the ultrastructures of the three complexes were analyzed by electron microscopy. In contrast to aggregated (C5b‐7)nand (C5b‐8)n, negatively stained SC5b‐7 and SC5b‐8 imaged mostly as monomeric irregularly shaped cylindrical structures, whereas SC5b‐9<27 S) appeared as wedge‐shaped structure lacking the tubular polymerized C9. (All three complexes were also generated in the presence of biotinyl‐S‐protein and labeled with avidin‐gold conjugates as electron‐dense marker). Analysis of the modified complexes in electron micrographs demonstrated that the complexes were marked exclusively at one site of their ultrastructures, suggesting this region to be the location of S‐protein and the critical site for membrane binding of C5b‐7 or C5b‐8 and for initiation of C9 polymerization. These results support recent findings in which the function of S‐protein as complement inhibitor was dependent on conformational changes of the protein molecule with concomita

ISSN:0014-2980    

DOI:10.1002/eji.1830190112

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractRecently, it has been shown that cloned L1/1 T helper cells of type 2 (TH2 ‐cells), when stimulated with antigen, are able to induce polyclonal B cell proliferation. Here we present evidence that this process is dependent on direct cell‐cell interaction between T and B cells, which in the effector phase,i.e., during stimulation of the B cells by activated T cells, can be mediated by a mechanism other than cognate interaction. This conclusion is derived from experiments in which highly purified, small B cells of high density were polyclonally stimulated by L1/1 T cells triggered by an anti‐T3 monoclonal antibody in the absence of antigen. The triggering process was independent of the presence of the Fc part of the antibody and occurred in cultures devoid of macrophages. Thus, the well‐established cognate recognition does not appear to be the only mechanism of B cell induction by T helpe

ISSN:0014-2980    

DOI:10.1002/eji.1830190113

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractThe responses of a single cloned T cell line to three different class II major histocompatibility complex (MHC) ligands have been compared for avidity, determined by inhibition with anti‐T cell receptor Fab fragments directed at two different receptor epitopes, and for ease of inhibition with anti‐CD4 antibody. It has, thus, been directly demonstrated that ease of inhibition of the response of a T cell to a class II MHC ligand by anti‐CD4 is inversely related to the avidity of the T cell receptor for that ligand. The difficulties in inferring from this finding that CD4 acts primarily by increasing receptor avidity for its class II MHC ligand are discussed in the light of evidence suggesting that CD4 is an active signaling component of the T cell receptor for class II MHC li

ISSN:0014-2980    

DOI:10.1002/eji.1830190114

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractTwo clones, E2‐7.7 and E2‐10.50, derived from two macrophage(MΨ)hybridomas, E2‐7 and E2‐10, have been studied. The first clone, E2‐7.7, is Ia and Fc receptor (FcR) negative and manifests a strong antigen‐presenting capacity. When we pulsed its cellsin vitrowith keyhole limpet hemocyanin (KLH) antigen and injected them into syngeneic animals, we found that as small a dose as 103cells initiated an immune responsein vivo.On the other hand, antigen‐pulsed cells of the E2‐10.50 clone, which are Ia‐and FcR, were almost incapable of triggering immunity, even when injected at a dose of 105cells. Thus, the two clones differ in their immunogenic capacity (both cellular and humoral immunity). In experiments aimed at testing the stimulationin vitroof primed lymph node (LN) cells by antigen‐pulsed cells of these two hybridoma clones, we observed that E2‐7.7 stimulated the unfractionated population of LN cells and the LN‐derived population of T cells. The E2‐10.50 cells stimulated only the unfractionated population of LN cells, but not the T cell population. Subsequent tests indicated that the E2‐10.50 cells require an intermediate Ia accessory cell to present the antigen to the T lymphocytes.Analyzing the molecular structure of the MΨ hybridomas, we discovered that major histocompatibility complex (MHC) genes of the myeloma haplotype (H‐2d), and of the splenic MΨ used for fusion (H‐2k), which were not expressed in the parental myeloma or in the E2‐10.50, were expressed in the E2‐7.7. Thus, somatic cell fusion of MΨ resulted in the activation of suppressed genes of the myeloma partner. It appears that these antigens participate in controlling the immunogenic properties of the E2‐7.7 clone. Testing the effects of interferons on the MΨ hybridomas, we observed that interferon‐γ activated, at both the mRNA and the cell surface‐antigen levels, the expression of H‐2Dk, H‐2Kdand H‐2Ddin the E2‐10.50 cells, but not in the E2‐7.7. Consequently, interferon‐γ augmented significantly antigen presentation by E2‐10.50 but not by E2‐7.7 cells. These two hybridoma clones might represent two distinct subsets of normal MΨ, manifesting two different sets of functional properties. Having described earlier the E2‐10.20 clone that takes up, but does not present antigen, we may in fact be facing three types o

ISSN:0014-2980    

DOI:10.1002/eji.1830190115

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractAnin vitrosystem for transforming immature lymphoid cells present in the thymus at early development has been established. By phenotype analysis of the transformants obtained, we observed that B cell precursors, susceptible to Abelson murine leukemia virus (A‐MuLV)‐ or Harvey murine sarcoma virus (H‐MuSV)‐induced lymphogenesis, were present at high frequency in the fetal thymus of BALB/c mice. These precursors recolonized alymphoid thymus lobesin vitro, as do T cell precursors. It was further observed that B precursors in the fetal liver were also capable of recolonizing alymphoid thymus lobes and were stored in a thymic environment. These results suggest that stroma cells of the fetal thymus may possess the capacity to support the growth of B precursors. On the other hand, B cell precursors sensitive to the viral transformation were undetectable in the fetal thymus of C57BL/6, although immunohistochemical analysis suggested their presence. However, in the fetal liver of the same strain, B precursors recolonizing alymphoid thymusin vitrowere sensitive to the viral transformation. Based on these results, we will discuss both the role and fate of thymic B precursors. In addition, we also obtained T cell lymphomas at different stages of differentiation from the fetal thymus of C57BL/6 infected with A‐MuLV or H‐MuSV. These data indicate the usefulness of our system in establishing cell lines derived from intrathymic lymphogenesis at early

ISSN:0014-2980    

DOI:10.1002/eji.1830190116

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractIn this study we investigated the basis for immunity or tolerance to a mouse serum protein, the fifth component of complement (C5). In C5‐deficient mice this protein is absent from serum and therefore they are not tolerized. Immunization of C5‐deficient mice with C5‐sufficient serum generates CD4 T cells, which recognize C5 presented in the context of class II. No C5‐specific responses were observed in T cells from C5‐sufficient mice. We show that this self protein is processed and presented with class II by cells from C5‐sufficient tolerant mice and can be recognized by C5‐specific T cell clones and hybrids in the absence of exogenously added antigen. The stimulation of C5‐specific T cells by C5‐sufficient antigen‐presenting cells is not a consequence of C5 secretion and subsequent processingin vitrobut rather employs C5 peptide/class II complexes generatedin vivo.We conclude that this self antigen is presented in normal mice in a form recognizable by T cells to induce and maintain immu

ISSN:0014-2980    

DOI:10.1002/eji.1830190117

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractThe thymus has been shown to play an important role in the generation of T cell tolerance to self antigens. Developing T cells are readily tolerized to antigens which are expressed in the thymus, and it is generally thought that such thymic tolerance occurs by a mechanism of clonal deletion. We sought to examine whether T cells which initially encountered a “self antigen” post‐thymically would be rendered tolerant of that antigen, and if so whether the mechanism of tolerance induction would differ from that found for thymic antigens. We constructed bone marrow radiation chimeras which were grafted with two thymus lobes differing in minor histocompatibility antigens. T cells which matured in one thymus would be tolerized to the minor histocompatibility antigens expressed in that thymus but would not encounter, and would therefore have no early opportunity of being tolerized to the minor histocompatibility antigens expressed by the other thymus. The initial encounter with the minor antigens on the second thymus would occur post‐thymically. Would these T cells be tolerant or responsive to those minor histocompatibility antigens? We found that tolerance was dominant in these chimeras. The data further suggest that the mechanism responsible for tolerance induction in the periphery may differ from that which operates in the

ISSN:0014-2980    

DOI:10.1002/eji.1830190118

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractLymph node cell populations derived fromTrypanosoma brucei‐infected mice fail to produce interleukin 2 (IL 2) in response to a potent mitogenic trigger and suppress the potential of normal lymph node cells to secrete IL 2 in co‐culture assays. This suppression is promptly restored by the addition of indomethacin, which blocks prostaglandin synthesis, but is not markedly affected by the addition of catalase, which degrades H2O2. The suppression of the IL 2 receptor expression, on the other hand, is not restored by the addition of indomethacin, nor by the simultaneous supply of both indomethacin and catalase. This discrepancy is not caused by an extreme susceptibility of the receptor expression to low prostaglandin (PG) concentrations, but rather by the presence of suppressive cells that operate through a PG‐independent mechanism. This suppressive mechanism accounts for the loss of the IL 2 receptors on both the Ly‐2 and the L3T4 T cell compartment. The indomethacin‐treated co‐cultures, which manifest a normal IL 2 production but lack the IL 2 receptors, manifest an impaired DNA synthesis and contain a decreased number of T

ISSN:0014-2980    

DOI:10.1002/eji.1830190119

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractSelective inhibition by pertussis toxin (PT) of mitogenic activation of mouse B lymphocytes by bacterial mitogens (peptidoglycan and lipopolysaccharide) and muramyl dipeptide (a synthetic analog of peptidoglycan fragment) was demonstrated. Mitogenic activation of B cells by protein kinase C activators and ionomycin was insensitive to PT. Also PT did not inhibit peptidoglycan‐ and lipopolysaccharide‐induced differentiation of B cells into Ig‐secreting cells, when it was added to the cultures after the proliferative stage of the response. B lymphocyte membranes contained two major PT substrates (40 and 41 kDa). The extent of PT‐mediated ADP ribosylation of these substrates correlated with the degree of PT‐mediated inhibition of mitogenic stimulation of B cells. B cell stimulation by all mitogens tested was not inhibited by cholera toxin at nontoxic concentrations that are known to cause maximal increase in cAMP in B cells. Since the only known substrates for PT‐mediated ADP ribosylation in mammalian cells are the α subunits of some G proteins, our data suggest that G proteins are present in B cell membranes and that they are involved in B cell activation induced by bacter

ISSN:0014-2980    

DOI:10.1002/eji.1830190120

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractSequential sublining was used in combination with enzyme‐linked immunosorbent assays to isolate μ → γ isotype switch variants of the rat IgM secreting mouse‐rat B cell hybridoma line BA1.8. Switch variants to all four subclasses of IgG were obtained. The variant antibodies retained the antigen specificity of the parental IgM for the O18 (lipopolysaccharide) antigen ofEscherichia coli.In sodium dodecyl sulfate‐polyacrylamide gels the apparent molecular mass of the γ heavy chains decreased in the order γ2b>γ1>γ2c>γ2a.IgM, IgG1, IgG2a, IgG2band IgG2cof the BA1.8 variant family and IgG2b, IgE and IgA of the previously described BA1.2 family were used for a comparative analysis of the capacity of rat Ig to activate complement. Efficient lysis of sheep erythrocytes coated with the O18 antigen was observed with IgM and all IgG subclasses, but no lysis was triggered by IgE or IgA. One hundred to 1000 IgG molecules were required to mediate the same hemolytic activity as one IgM molecule. The four IgG subclasses were equally efficient at mediating lysis by rat or human complement, while IgG2awas less efficient with guinea pig complement than the other three IgG subclasses.Antibody‐triggered binding of C3 to pathogenic O18: K1E. colibacteria was measured using serum containing125I‐labeled C3. K1‐encapsulated strains did not fix C3 efficiently in the absence of specific antibodies while acapsular mutants fixed C3 via the alternative pathway. IgM and all IgG subclasses triggered C3 binding to the K1 encapsulated bacteria. The capacity of IgM to mediate C3 fixation was not greater than th

ISSN:0014-2980    

DOI:10.1002/eji.1830190121

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY