摘要:

AbstractActivated human T cells express class II molecules, but their capacity to present soluble antigens and stimulate T cells has been repeatedly questioned. Two lines of evidence indicate that T cells may indeed function as professional antigen‐presenting cells. First, T cells that have been recently activated can efficiently capture, process and present tetanus toxoid to class II‐restricted T cell clones. This capacity correlates with the rate of class II synthesis. Second, activated T cell clones express high levels of B7, are powerful stimulators in mixed lymphocyte reactions, and their stumulatory capacity is inhibited by soluble CTLA4 or anti‐B7 antibody. Furthermore, expression of B7 can be detectedin vivoon T cells from biopsies of patients with liver disease. Presentation of soluble antigen by activated T cells may play a role in the amplification of the specific response, and possibly in immunopathological s

ISSN:0014-2980    

DOI:10.1002/eji.1830240112

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractIn our prior study it was demonstrated that residues 46 and 54 on a synthetic peptide, AEGFSYTVANKNKGIT (50V), work as an agretope (site contacts with major histocompatibility complex molecules) and residues 50 and 52 function as an epitope (site contacts with T cell receptor), when tri‐molecular complexes are formed among 50V, I‐Aband the T cell receptor. 50V was composed of residues 43 to 58 of pigeon cytochromec(p43‐‐58) except that the aspartic acid (D) at residue 50 was substituted by valine (V). Substitution of agretopic residues on 50V changed this I‐Ab‐binding peptide to an I‐Ak‐binding peptide, suggesting that positions 46 and 54 work as an agretope in I‐Ak‐restricted T cell responses. In the present study we examined whether residues 46 and 54 of 50V worked as agretopes in T cell responses restricted to other I‐A haplotypes. The 50V‐related peptides with phenylalanine (F) at position 46 and alanine (A) at position 54 bound tightly to I‐Ab, I‐Ad, I‐Aqand I‐Asmolecules and stimulated T cells most potently in mice bearing these I‐A haplotypes. In contrast, 50V‐related peptides carrying D at position 46 and A at position 54 bound most potently to I‐Akmolecules, and the peptides with arginine (R) at position 46 and A at position 54 bound most efficiently to I‐Avmolecules. The present findings, thus, demonstrate that the agretopic positions on the p43‐‐58 related peptides are preserved in T cell responses restricted to each I‐A haplotype studied, and that the specific amino acids on the agretopic positions exist a

ISSN:0014-2980    

DOI:10.1002/eji.1830240113

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractSelective pairwise interactions between CD3 chains and the clonotypic T cell antigen receptor (TCR)‐α, ‐β chains has recently been established. In this study, the region of interaction between clonotypic and CD3 chains involved with assembly was examined. To determine the site of protein interaction a variety of genetically altered TCR chains were constructed. These included: truncated proteins, lacking transmembrane and or cytosolic domains; chimeric proteins, in which extracellular, transmembrane or cytosolic domains were replaced with similar domains derived from either the Tac antigen or CD4; and point mutagenized TCR chains. COS‐1 cells were transfected with cDNA, metabolically labeled, and immunoprecipitates analyzed using non‐equilibrium pH gel electrophoresis (NEPHGE)‐SDS/PAGE. The results demonstrated that assembly between TCR‐α and TCR‐β chains occurred at the extracellular level. Assembly of the TCR‐α chain with CD3‐δ, and CD3‐ε was localized to an eight‐amino acid motif within the transmembrane domain of TCR‐α. Site‐specific mutations of the TCR‐α charged residues within this motif ( arginine, lysine) to leucine and similar point mutations of the transmembrane CD3‐ε and CD3‐δ charge groups resulted in the abrogation of assembly. In contast, TCR‐β and CD3‐ε binary complexes interacted via their extracellular domain. Analogous to TCR‐α, the site of TCR‐β and CD3‐δ assembly was at the transmembrane region. Despite multiple genetic manipulations on CD3‐γ and ζ; these proteins failed to assemble with TCR‐α. Similarly, there was no interaction between TCR‐β and ζ. These findings when coupled with the information on pairwise interactions and formation of higher orde

ISSN:0014-2980    

DOI:10.1002/eji.1830240114

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractRheumatoid arthritis patients were found to have CD4+T cells that proliferate in response to autologous synovial fluid and plasma. T cell clones and polyclonal T cell lines were found to respond to antigen(s) eluted from protein A Sepharose and anti‐human immunoglobulin (Ig) antibody Sepharose. The antigen(s) was further resolved to fractions that contained intact Ig or Ig heavy chain since the T cells responded to>100 kDa and 40‐‐60 kDa polypeptides derived from purified Ig under nonreducing and reducing conditions, respectively. These results indicated that the antigen(s) is either Ig heavy chain or Ig‐binding proteins that copurify with Ig and Ig subunits. Pepsin and papain digestion of the antigenic fractions eluted from protein A destroyed the T cell reactivity. Since most Fab regions are resistant to these enzymes, further analyses are required to localize the antigenic epitope(s). The presence of Ig‐ or Ig‐antigen complex‐reactive T cells in arthritic joints implies that B cells expressing anti‐Ig antibody (i.e.rheumatoid factor) may play an important role in antigen presentation to autor

ISSN:0014-2980    

DOI:10.1002/eji.1830240115

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractN‐terminal sequencing of the 55‐ and 50‐kDa polypeptides affinity purified on a phosphotyrosine monoclonal antibody column from activated Jurkat T cells identified α and β tubulin. Two‐dimensional gel analysis indicated that α tubulin was directly phosphorylated on tyrosine. β Tubulin was not detectably tyrosine phosphorylated but was precipitated by anti‐phosphotyrosine (PTyr) antibody by virtue of its association with the α subunit as a heterodimer. Phosphotyrosyl α tubulin was not incorporated into intact microtubules and was all in the unpolymerized soluble fraction. These results suggest that tyrosine phosphorylation of α tubulin may inhibit the ability of this subunit to polymerize into microtubules. Stimulation of Jurkat T cells via T cell receptor increased the amount of tubulin precipitated by the anti‐PTyr antibody. These data raise the possibility that the polymerization of tubulin heterodimers may be regulated by phosphorylation on tyrosine during

ISSN:0014-2980    

DOI:10.1002/eji.1830240116

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractThe complex genomic organization of the murine T cell receptor (TcR) δ‐α region has hindered detailed studies of α gene rearrangement and Jα gene usage in individual differentiating T cell precursors. We have isolated a novel set of Jα probes which, in combination with a few restriction enzyme digests, enable a reliable, simple and nearly complete analysis and location of any rearrangement at the Jα locus by conventional Southern blotting. The probes were used to analyze TcR α gene rearrangements in T cell hybridomas derived from anin vitroculture system that supports T cell differentiation of bone marrow cells. Our results indicate that Jα genes are unequally accessible for rearrangement and two hot spots for rearrangement could be demonstrated. In addition, only a restricted set of Jα genes was rearranged in each culture indicating that the slightly variable composition of factors can influence the recombinatorial accessibility of Jα genes. The hot spots for rearrangement were not only limited to T cells differentiatingin vitrobut could also be demonstrated among functional T cell clones based on the published sequence information from isolated TcR α gene rearrangements. The demonstration and the location of the hot spots for rearrangement in the T cell differentiation culture system opens up the possibility to study factors and mechanisms that regulate recombinatorial accessibility of

ISSN:0014-2980    

DOI:10.1002/eji.1830240117

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractT cell‐dependent regulation of B cell growth and differentiation involves an interaction between CD40, a B cell surface molecule, and the CD40 ligand (CD40L) which is expressed on activated CD4+T cells. In the current study, we show that recombinant membrane‐bound murine CD40L induces B cells to express costimulatory function for the proliferation of CD4+Tcells. CD40L‐ or lipopolysaccharide (LPS)‐activated, but not control‐cultured B cells were strong costimulators of anti‐CD3 or alloantigen‐dependent T cell responses. The molecular interactions responsible for the increased costimulatory functions were examined by analyzing the activated B cells for changes in the expression of two costimulatory molecules, B7 and heat‐stable antigen (HSA), as well as by the use of antagonists of B7 and HSA (CTLA4.Fc and 20C9, respectively). The expression of both B7 and HSA was enhanced on B cells activated with LPS. As observed in previous studies, the costimulatory activity of the LPS‐activated B cells was dependent on both B7 and HSA and was completely inhibited in the presence of a combination of CTLA4.Fc and 20C9. In contrast, activation of B cells with CD40L induced the expression of B7 but did not enhance the expression of HSA. In addition the costimulatory activity of the CD40L‐activated B cells was partially, but not completely, inhibited by the combination of CTLA4.Fc and 20C9. These results demonstrate that CD40L regulates costimulatory function of B cells in part by inducing the expression of B7 and suggest that CD40L‐activated B cells express an additional costimulatory activity that is not associated with

ISSN:0014-2980    

DOI:10.1002/eji.1830240118

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractInterleukin‐6 (IL‐6) mediates pleiotropic functions through specific receptors (IL‐6R) composed of an 80‐kDa binding protein, associated with a non‐ligand binding protein (gp130) which transduces the signal. Because IL‐6 is the major tumor growth factor in multiple myeloma, we investigated the regulation of IL‐6R in two human multiple myeloma cell lines. Binding experiments with125I‐labeled IL‐6 showed that IL‐6R were expressed at a high density on RPMI‐8226 cells (15 000 receptors/cell), but no specific binding was detected on XG‐1 cells, whose growth depends on the presence of exogenous IL‐6. However, when IL‐6 was removed from the culture medium, high‐affinity IL‐6R appeared on the surface of XG‐1 cells (5300 sites/cell). Treatment of RPMI‐8226 cells with IL‐6 reduced the number of IL‐6R without changing their affinity. This reduction was dose dependent and was not affected by acid treatment which dissociates ligand‐receptor complexes. Cross‐linking experiments showed that the formation of one IL‐6/receptor complex of 160 kDa markedly decreased upon IL‐6 treatment, while the other complex of 190 kDa became undetectable. These data provide evidence for ligand‐induced down‐regulation of membrane IL‐6R expression in myeloma cells. Treatment of RPMI‐8226 cells with interferon‐α (IFN‐α), which inhibits the growth of these cells, stimulated IL‐6R expression and increased the formation of the 160‐kDa IL‐6/receptor complex. This stimulation was specific for IFN‐α, since IFN‐γ reduced the number of IL‐6R. These data indicate t

ISSN:0014-2980    

DOI:10.1002/eji.1830240119

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractThe genes encoding the heavy and light chains of a murine monoclonal antibody (mAb Guy's 13) have been cloned and expressed inNicotiana tabacum.Transgenic plants have been regenerated that secrete full‐length Guy's 13 antibody. By manipulation of the heavy chain gene sequence, constant region domains from an immunoglobulin alpha heavy chain have been introduced, and plants secreting Guy's 13 mAb with chimeric gamma/alpha heavy chains have also been produced. For each plant antibody, light and heavy chains have been detected by Western blot analysis and the fidelity of assembly confirmed by demonstrating that the antibody is fully functional, by antigen binding studies. Furthermore, the plant antibodies retained the ability to aggregate streptococci, which confirms that the bivalent antigen‐binding capacity of the full length antibodies is intact. The results demonstrate that IgA as well as IgG class antibodies can be assembled correctly in tobacco plants and suggest that transgenic plants may be suitable for high‐level expression of more complex genetically engineered immunoglobulin molecules. Since mAb Guy's 13 prevents streptococcal colonization in humans, transgenic plant technology may have therapeutic applica

ISSN:0014-2980    

DOI:10.1002/eji.1830240120

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractCD2 is a cell surface receptor molecule which has been implicated in cell‐cell adhesion and signaling functions in T lymphocytes and natural killer cells. The mechanism by which extracellular stimuli induce CD2‐regulated signal transduction events is largely unknown. However, there is increasing evidence that in cells of hematopoietic origin several receptor‐mediated signaling mechanisms involve transmembrane polypeptides related to the CD3 ζ chain and the activation of protein tyrosine kinases. We have therefore investigated the potential involvement of ζ chain andsrcfamily protein tyrosine kinases in signal transduction pathways initiated by CD2. Usingin vitrokinase assays on CD2 immunoprecipitates from detergent lysates of T lymphocytes, we identified a complex consisting of CD2, ζ chain and thesrcfamily kinases p59fynand p56lck. Furthermore, using double indirect immunofluorescence combined with capping techniques, we have revealed such complexes in viable T lymphocytes. These findings provide evidence for a multimolecular signaling complex consisting of at least CD2, ζ chain and p59fynin T lymphocytes and suggest a critical role for this complex in the initiation of CD2‐mediated cellular activation by regulating the activation of intracellular signalin

ISSN:0014-2980    

DOI:10.1002/eji.1830240121

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY