摘要:

AbstractThe biochemical behavior and peptide binding properties of a soluble form of the human class II DR4Dw4 molecule (PI‐DR4Dw4) were compared to DR4Dw4 molecules containing the transmembrane and cytoplasmic domains that were purified both from B and transfected Chinese hamster ovary cells. Recombinant and B cell‐derived DR4Dw4 molecules bound monoclonal anti‐DR4Dw4 antibodies with different affinities and varied in their stability in the presence of sodium dodecyl sulfate. The three forms of DR4Dw4 bound peptides with a similar apparent affinity constant, but soluble class II molecules bound up to ten times more peptide than DR4Dw4 containing a transmembrane region. Peptide binding kinetics for soluble DR4Dw4 molecules were 10‐20 times faster than for the other two forms of DR4Dw4 molecules. Finally, soluble PI‐DR4Dw4/peptide complexes were shown to stimulate T cell prol

ISSN:0014-2980    

DOI:10.1002/eji.1830230112

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractResting murine B lymphocytes can be induced to proliferate by cross‐linking membrane immunoglobulin, the antigen receptor, or by contact with activated helper T lymphocytes in the absence of a signal through membrane immunoglobulin. Little is known about the molecular nature of contact‐dependent T cell help. To determine whether helper T cells activate B cells through different signal transduction and second messenger pathways from those used by membrane immunoglobulin, the effects of drugs which block activation of B cells through membrane immunoglobulin were measured on B cell activation by contact with anti‐CD3‐activated and fixed T helper cells. Cyclosporin A, phorbol esters added at the time of activation, and cAMP agonists all block activation of B cells through membrane immunoglobulin at concentrations at least 100‐fold lower than those necessary to block B cell activation by contact with activated Th1 or Th2 helper T cells. Depletion of protein kinase C by pretreatment of B cells with phorbol ester inhibits the proliferative response to anti‐immunoglobulin but not the response to contact with activated T cells. The B cell response to lipopolysaccharide is intermediate in sensitivity to cyclosporin A and cAMP agonists, and resembles the response to activated T cells in resistance to phorbol esters and protein kinase C depletion. Various protein kinase inhibitors did not distinguish among these B cell activation pathways, except for the tyrosine kinase inhibitor, herbimycin A, which inhibited anti‐immunoglobulin responses at 3‐ to 5‐fold low

ISSN:0014-2980    

DOI:10.1002/eji.1830230113

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractWe have recently shown that activation of T cells causes structural changes in the interleukin‐7 receptor (IL‐7R) (Foxwell et al.Int. Immunol.1992.4: 277). Unactivated cells expressed a receptor characterized as a cross‐linked protein of 107‐kDa whereas activated cells had reduced levels of this 107‐kDa complex and now express a major cross‐linked product of 93 kDa. These changes in receptor expression were concomitant with the acquisition of IL‐7 growth responsiveness by activated T cells. In this study, the effect of the potent immunosuppressive agents cyclosporin A and FK506 on the activation‐induced responsiveness to IL‐7‐driven proliferation and the concomitant changes in receptor structure have been investigated. Cyclosporin A and FK506 suppressed the expression of the 93‐kDa complex and the loss of the 107‐kDa complex on activated cells. The presence of exogenous IL‐7 inhibited the effects of the drugs on IL‐7R structure, allowing expression of the 93‐kDa complex. Expression of the 93‐kDa complex could also be induced either by ionomycin or phorbol esters. As observed for other T cell activation parameters, only those which induced a calcium signal (ionomycin) but not protein kinase C (phorbol esters) were sensitive to the drugs. In all studies, the expression of the 93‐kDa complex correlated with the ability of cells to proliferate to IL‐7, and thus these results further support the hypothesis that the 93‐kDa form of the IL‐7R is required to transmit the cytokine's growth signal. Moreover, these data suggest that activation‐induced transcriptional events are required for the expression of the 93‐kDa complex and the down‐regulation of the 107‐kDa complex. As reported for IL‐2R and IL‐4R, our data also show that the expression of another T cell growth factor receptor is sensitive to the effects of cyclosporin A and FK506. These observations also have important implications for reported cyclosporin A effects on the thymus w

ISSN:0014-2980    

DOI:10.1002/eji.1830230114

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractThe T cell response to allogeneic murine Mls determinants is not H‐2 restricted but is dependent on H‐2 class II molecules on the Mls‐expressing stimulator cells. We have tested planar membranes containing H‐2 class II I‐E molecules alone or with I‐A molecules for their ability to activate a panel of Mls1a‐specific T hybrids. Despite the ability of the planar membranes to activate an alloreactive T hybrid and to present staphylococcal enterotoxins or an antigenic peptide to appropriately responsive T hybrids, they failed to stimulate the Mls1a‐specific T hybrids. These findings, in the light of the various controls demonstrating sufficiency of the I‐E molecules in the planar membranes, indicate that Mls1adeterminants are not covalently bound to I‐E molecules; the two molecular species are thus either not physically associated or are linked by a relatively weak interaction. In addition, our experiments show that isolated I‐E molecules but not I‐A molecules present staphylococcal enterotoxins A and B to two independently derived T hybrids expressing T cell receptor Vβ1

ISSN:0014-2980    

DOI:10.1002/eji.1830230115

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractBy selective labeling of juvenile chicken bursal cells with colloidal fluorescein isothiocyanatein situ, the emigration rate of bursal lymphocytes to the periphery was estimated at approximately 0.84% and 0.96% of the peripheral blood lymphocyte (PBL) and splenic B cell pool per hour, respectively. Emigrant bursal cells were found primarily in blood and spleen, with very small numbers migrating to thymus, bone marrow, and gut‐associated lymphoid tissues. Emigrant bursal cells expressed high levels of both major histocompatibility complex class II antigen and the Ov alloantigen, a phenotype found on a population comprising approximately 4% of bursal cells from which the bursal emigrants may be derived. Surgical bursectomy at 3 weeks of age revealed that peripheral blood B cells could be divided into three distinct populations. Specifically, 60% of the peripheral blood B cells were short lived with a half‐life of about 30 h in the blood. These cells accounted for the great majority of emigrants from the bursa to the peripheral blood. Approximately 35 % of PBL B cells had a half‐life of 12 days following bursectomy and comprised cells which did not divide in the periphery. Consequently, we propose that physiological differences between this population and the majority of bursal emigrants are established intrabursally. The remaining PBL B cells, whose relative proportion increases with age from about 5 % of PBL B cells at 2‐3 weeks of age, are short lived and are being continually produced from (a) post‐bursal site(s) of B cell p

ISSN:0014-2980    

DOI:10.1002/eji.1830230116

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractRat CD4+T cells are divided phenotypically by the anti‐CD45RC monoclonal antibody OX22 into subsets with contrasting functions. Stimulation of T cellsin vitrois known to induce a change in isoform from CD45RC+to CD45RC−. We have investigated thein vitroconditions which promote a switch in isoform in the opposite direction. We observed that a majority of CD45RC−CD4 T cells (>90%) spontaneously re‐expressed CD45RC during the first 1‐3 days of culture in both the presence and absence of alloantigen. The T cells remained CD45RC+when cultured for 7 days in serum‐free growth medium. However, alloantigen‐activated lymphocytes, expressing the interleukin‐2 receptor (IL‐2R), down‐regulated CD45RC by day 4 and remained CD45RC−during the course of the experiment. Using mixtures of allotype‐marked CD45RC+and CD45RC−T cells, it was demonstrated that each subset showed comparable survival, IL‐2R expression and time courses of activation in response to alloantigen. The repertoire of neither subset was, therefore, deficient in terms of allorecognition. The rapid re‐expression of CD45RC in culture was accompanied by a change in function: CD45RC+“converts”, obtained by overnight culture of CD45RC−T cells, induced significantly higher graft‐versus‐host responses. Thus, the transition in culture from CD45RC−to CD45RC+reflects a major functional reprogramming of the cell and not

ISSN:0014-2980    

DOI:10.1002/eji.1830230117

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractThe repertoire of immunoglobulin expressed very early in human development was approached by cloning and sequencing 55 rearranged and 11 germ‐line VH transcripts, after amplification by polymerase chain reaction of cDNA libraries derived from two fetal livers at 8 and 13 weeks of gestation. All families with the exception of VH2, were expressed as soon as 8 weeks, with preferential usage of certain germ‐line genes. Very few somatic mutations, randomly localized, were identified. By contrast, in a series of clones derived from the same VDJ rearrangement using the VH6 family, extensive mutations had taken place, mostly accumulated in the third complementarity‐determining region (CDR3) suggesting that the specialized enzymatic machinery was at hand very early during human development.Some other characteristics of the fetal repertoire also emerged, namely increased usage of JH3 and JH2, as compared to the adult pattern, where JH4 is dominant and reduced length of the D/CDR3 regions. All D gene families were identified, and their usage frequently involved D‐D fusions. N diversity was present very early, and increased with age.Identification of germ‐line transcripts pertaining to all six VH families including pseudogenes, in the E55 library, revealed a population very different as compared to rearranged gene transcripts. This suggests that a large portion of VH locus is accessible for transcription, bringing no evidence of correlation between preferential rearrangement of a given VH gene and its localization in

ISSN:0014-2980    

DOI:10.1002/eji.1830230118

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractCD2‐associated molecules were identified by means ofin vitrokinase assays of CD2 immunoprecipitates obtained from nontransformed human T lymphocytes lysed in the detergent brij 58. Under these conditions CD2 was found to be associated with the protein tyrosine kinases p56lckand p59fynas well as two low molecular weight phosphoproteins. The latter were identified as the ζ and ϵ chains, the major signaling components of the CD/7 TcR complex. Importantly, induction of T cell unresponsiveness towards CD2‐mediated stimuli by means of CD3/Tcell receptor (TcR) modulation results in uncoupling of ζ and ϵ from the CD2 molecule, while its associations with p56lckand p59fynremain unaffected. Moreover, despite the incapacity of T lymphocytes to undergo DNA synthesis in the CD3/TcR‐modulated state, CD2 triggering still results in tyrosine phosphorylation of some unknown protein substrates. Thus, the same ζ and ϵ chains which are components of a functional TcR complex appear to also couple to the CD2 molecular complex. Moreover, dissociation of TcR and CD2 complexes in intact cells seems to block CD2‐mediated Tcell growth but does not result in complete abolishment of the signal transducing capacity of the

ISSN:0014-2980    

DOI:10.1002/eji.1830230119

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractIn the memory response to the phosphorylcholine hapten (PC) two major groups of anti‐PC antibodies with different fine specificities are elicited. Group I antibodies are mainly PC specific, whereas Group II antibodies are comprised of two specificities directed against the phenyl‐PC and the phenyl moiety of the PC hapten. The VLgene usage of 17 monoclonal memory anti‐PC antibodies were investigated by Southern blot analysis and nucleotide sequencing. Six out of eight Group I memory PC‐specific antibodies used the same VK22‐JK5 rearrangement as the major T15 primary response idiotype. One expressed a mutated JKI and one employed another VK22 gene family member. A shift in specificity from PC (Group I) towards phenyl‐PC (Group II) was accompanied with the usage of either VK1C‐JK1 or VK1A‐JK5 rearrangements. The phenyl‐specific Group II antibodies expressed the Vλl‐JλL chain rearrangement in combination with VHM141 expressing H chains. In this specific segment of Group II antibodies most mutations were found. Thus four different VLgenes were found to contribute to the fine specificity of memory response antibodies to the PC hapten in a clear structure‐function relationship. The diversified fine specificity in the memory response derives mainly from the usage of different L chains with particular VJ rearrangements in combination with VHof the dominant initial response clonotype and is not primarily d

ISSN:0014-2980    

DOI:10.1002/eji.1830230120

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractThe T cell growth factor interleukin‐2 (IL‐2) induces p21rasactivation in T lymphocytes. We have previously shown that a protein kinase C (PKC)‐mediated pathway for p21rasregulation exists in T cells and that the IL‐2 receptor (IL‐2R) can couple to p21rasindependently of the presence of the PKC pathway for p21rasregulation. Our data show that in conditions where cellular protein tyrosine kinases (PTK) were efficiently down‐regulated by pretreatment with the specific PTK inhibitor herbimycin, the IL‐2‐induced activation of p21raswas blocked. Herbimycin did not inhibit the PKC‐mediated pathway for p21rasregulation. Thus, the data indicate that PTK are involved in the coupling of th

ISSN:0014-2980    

DOI:10.1002/eji.1830230121

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY