摘要:

AbstractA proportion of T cells recirculate in a tissue‐selective manner. Recent studies which showed that the skin‐tropic subset of T cells was of memory/activated type, led us to examine whether the preferential homing of T cells to the gut also involved memory T cells, and if so whether these memory T cells were phenotypically distinct from other memory T cells. Lymphocytes migrating through the gut and the skin of sheep was collected by cannulating the lymphatic ducts draining these tissues. Both naive and memory T cells were found to recirculate through the gut, although only memory T cells migrated through the skin. However, when T cells from the gut were labeled with fluorescein isothiocyanate and assessed for their migration back to the gut, it was the memory population which showed a tropism for the gut. Gut‐tropic memory T cells migrated poorly through the skin, indicating that these cells were distinct from skin‐tropic memory T cells. This was confirmed by phenotypic analysis. Gut memory T cells expressed very low levels of the α6 and β1 integrins, in contrast to skin memory T cells which expressed high levels. There was no evidence for heterogeneity within the naive T cell population, which migrated preferentially to lymph nodes. This migration pattern could be explained in part by the high expression of the L‐selectin (lymph node homing receptor, LAM‐1) on naive T cells, in contrast to memory T cells from gut or skin which were mostly L‐selectin negative. These results in sheep indicate that subsets of α/β memory T cells show tissue‐selective migration patterns, which probably develop in a particular environment following enc

ISSN:0014-2980    

DOI:10.1002/eji.1830220402

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractThe expression and role of interleukin‐2/interleukin‐2 receptor (IL‐2/IL‐2R) system in the pokeweed mitogen(PWM)‐induced T cell mitogenesis was studied. In the absence of monocytes (Mo), both soluble and Sepharose‐bound PWM fail to induce T cell mitogenesis even when exogenous IL‐2 or IL‐1 or IL‐1+IL‐2 or IL‐4 are also present. In the presence of Mo, PWM stimulation of T lymphocytes (highly depleted of B lymphocytes) induces as much IL‐2 mRNA as phytohemagglutinin (PHA), but results in higher and persistent IL‐2 levels in culture supernatants despite the concomitant T cell mitogenesis, suggesting that PWM‐activated T cells do not utilize the IL‐2 they produce. Confirming this notion, Mo‐dependent PWM‐preactivated T cells, as compared to PHA‐preactivated ones: (a) failed to consume exogenous IL‐2 and their mitogenic response did not increase upon exposure to exogenous IL‐2; (b) exhibited very low numbers of high‐affinity IL‐2R; and (c) showed lower expression of IL‐2R p55 and undetectable expression of IL‐2R p75 on their surface. Moreover, the PWM‐induced T cell mitogenesis was not inhibited by anti‐IL‐2 or CD25 antibodies and only partially (50%–60%) inhibited by cyclosporin A, while these treatments abrogated the PHA‐induced one. PWM‐activated T cells, as compared to the PHA‐activated ones, exhibited as high (p55) or even higher (p75) mRNA expression of both IL‐2R p55 and p75 subunits. The possibility that PWM interferes with IL‐2R subunits once expressed on the T cell surface was excluded. Thus, intracellular PWM‐related events are likely to impair IL‐2R expression post‐transcriptionally. Possible explanations for this effect and its relation with the capacity

ISSN:0014-2980    

DOI:10.1002/eji.1830220403

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractInfluenza matrix peptide 58–66 is shown to be the optimal nonamer for binding to HLA‐A2 and presentation to cytotoxic T lymphocytes (CTL). If titered out to 2 × 10−10– 4 × 10−10M in CTL‐mediated lysis assays and to 3 × 10−9M in an HLA‐A2 assembly‐stabilization assay in cell lysates. The peptide was shown to make probable contacts with its carboxy terminus close to residue 116 in the floor of the cleft of HLA‐A2, close to the F pocket. The side chain of the amino‐terminal amino acid was unimportant, but its free amino and carbonyl groups in the A pocket appeared important in optimizing peptide presentation. The B pocket probably accommodates the side chain of residue 2 (isoleucine) and was shown to be critical

ISSN:0014-2980    

DOI:10.1002/eji.1830220404

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractThe effect of the synthetic glucocorticoid dexamethasone (DXM) on the secretion by human monocytes of alternative complement proteins C3, factor B and factor H was investigated. Results indicated that DXM modulates this secretion in a direction which would be consistent with its anti‐inflammatory properties. DXM, at therapeutic concentrations, had a suppressive effect on C3 and factor B secretion and a stimulatory effect on factor H secretion by monocytes. This differential modulation on C3, factor B and factor H secretion was similar in mature macrophages. Together with previous studies showing that DXM had a suppressive effect on C3 and factor B secretion and a stimulatory effect on factor H secretion by human endothelial cells, our results indicate that DXM appears to have the general property of regulating local production of complement components so as to control complement activatio

ISSN:0014-2980    

DOI:10.1002/eji.1830220405

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractThe cellular basis of the immune response underlying the granulomatous hypersensitivity in experimental murine schistosomiasis caused bySchistosoma mansoniwas investigated by examining a panel of 16 egg antigen‐specific T cell clones. The clones were derived from a sensitized T cell line by limiting dilution, and were selected on the basis of their strong responses against schistosomal egg antigens. By cytofluorographic analysis, it was determined that all clones were T helper cells and expressed the CD3+CD4+CD8−phenotype. Lymphokine analysis revealed that some clones secreted either interleukin (IL)‐2 or IL‐4, but a surprisingly large number were double producers. Southern blot analysis verified the clonality of these T cells and indicated that the clones examined included at least five independent clones by the criterion of T cell receptor β gene rearrangements. Despite their diversity, the clones responded strongly, and virtually exclusively, to egg antigen components with isoelectric points in the limited range of 4.7 to 5.2. The relevant antigenic egg molecules were shown to require processing by accessory cells for presentation to, and stimulation of, the T cel

ISSN:0014-2980    

DOI:10.1002/eji.1830220406

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractSurface peptidase activities on the human monocytic lineage cell line U937 were characterized. Two diisopropyl phosphofluoridate (DFP)‐inhibitable serine peptidases were identified by differences in their hydrolytic activities on chromogenic peptides: one removed tripeptides from the free NH2‐terminal end of the synthetic peptide Ala‐Ala‐Phe‐p‐nitroanilide (pNA) and was not inhibited by inhibitors of metallo‐, cysteic‐, and aspartic‐proteinases, or by those of elastase‐, trypsin‐ and chymotrypsin‐like enzymes, suggesting the presence of a hitherto unidentified serine tripeptidyl endopeptidase; the other peptidase catalyzed the release of Gly‐Pro from Gly‐Pro‐pNA and was inhibited by DFP, phenylmethyl sulfonyl fluoride and diprotin A, thus resembling dipeptidyl peptidase IV (DPP IV) with respect to its substrate specificity and inhibitor profile. A group of N‐exoaminopeptidase activities specifically inhibited by bestatin, was also detected when Ala‐, Leu‐, Arg‐ and Lys‐pNA were used as substrates. The activities were surface associated and not secreted as determined by extracellular location of product and enzymatic recovery in highly purified U937 cell membranes. Peripheral monocytes and macrophages were found to virtually exhibit identical levels of these two classes of peptidase activities when compared to those detected on U937 cells. The relative contributions of these hydrolytic enzymes to the cleavage of bioactive and radioiodinated cytokines including tumor necrosis factor‐α (TNF‐α), interleukin‐1α and interferon‐γ was next examined. The results indicated that N‐aminopeptidases do not appear to participate in the catabolism of any tested cytokine. In contrast, the most interesting finding was that both serine peptidases participate in TNF‐α degradation. Analysis of the final proteolytic digestion products demonstrated the disappearance of the native 17‐kDa molecule TNF‐α, and the concomitant release of biologically inactive fragments of ≤2 kDa. Together, these observations indicate new roles for both the DPP IV‐like enzyme and the tripeptidyl endopeptidase located at the surface of human monocytic cells, including the regulation of the extracellular TNF‐α concentration. Thus, the identification of functional ectopeptidases provides insight into

ISSN:0014-2980    

DOI:10.1002/eji.1830220407

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractPrevious studies from our laboratory have suggested that aging leads to an accumulation of cells expressing high levels of CD44, thought to be a marker for memory lymphocytes, and that positively selected CD44hiT cells, from mice of any age, respond poorly to concanavalin A (Con A) in limiting dilution estimates of interleukin (IL)‐2‐producing cells. We now report the results of a more comprehensive analysis of memory T cell function, in old and young mice, to non‐cognate activators (Con A and the staphylococcal enterotoxin SEB). We report that memory T cells, isolated by removing cells bearing the CD45RB determinant, contain very few cells able to respond to either Con A or SEB under limiting dilution culture conditions, whether the responses are measured by IL‐2 or by IL‐3 accumulation. As a control, we show that memory T cells do respond strongly, at limiting dilution, to recently encountered priming antigens,i.e. Schistosoma mansoniegg antigen; the limiting dilution culture protocol thus does not preclude activation of memory T cells when cognate stimuli are presented to antigen‐specific cells. These data suggest that virgin and memory T cells may differ fundamentally in their activation requirements, and suggest further that the accumulation, with age, of memory T cells accounts for the low responsiveness of old mice to non‐cog

ISSN:0014-2980    

DOI:10.1002/eji.1830220408

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractT cells bearing certain variable (V) regions of the T cell receptor (TcR), including Vβ3, Vβ6, Vβ8.1 and Vβ9, are stimulated by one or more forms of the endogenous superantigen, mouse lymphocyte stimulatory (Mls) locus, encoded by the mouse mammary tumor virus, in the context of a non‐polymorphic region of the class II molecules of the major histocompatibility complex (MHC). To identify putative sites of interaction of TcR‐Vβregion and Mls‐1a, we examined the effect of peptides derived from the protein sequence of Vβ6 on recognition of Mls‐1aby T cell hybridomas and show that three peptides corresponding to amino acid positions 1 to 20, 48 to 75, and 58 to 75 of the Vβ6 peptide sequence interfere with the activation of several Vβ6+hybridomas by Mls‐1a‐bearing spleen cells, but not with that of a Vβ8+hybridoma. The Mls‐reactive hybridomas are specific for a synthetic peptide poly‐18, poly EYK(EYA)5and its peptide (EYA)5, in the context of I‐Ad. This peptide does not require processing and the peptides 1–20, 48–75, and 58–75 do not inhibit recognition of (EYA)5by the same Vβ6+T cell hybridomas. The two sequences 1–20 and 58–75 are proposed to lie outside the putative binding domain of processed antigen, indicating that recognition by TcR of Mls‐1ais different from the classical MHC‐restricted recognition of processed antigen. These results suggest that the recognition of superantigen/class II MHC by T cells can be inhibited by peptides related to the site of interaction of the TcR, suggesting that such peptides could have possible regulatory effects on the ind

ISSN:0014-2980    

DOI:10.1002/eji.1830220409

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractThe majority of T cell hybridomas produced in the BALB/c mouse in response to immunization with λ, repressor cI recognize a peptide fragment comprising of residues 12 to 26 (P12–26). Some other parts of the cI (P1–14, P33–48 and P73–88) are defective in generating T cell responses in the BALB/c mouse. P73–88 may be converted into a T cell determinant if a few more amino acid residues are included (P67–88). Together with P46–67 and P80–102, most peptides derived from cI were capable of eliciting T cell responses by themselves in BALB/c mouse. The mechanisms underlying the selection of P12–26 over the other epitopes when λ repressor was used as immunogen were examined. The dominant response to P12–26 was attenuated by tolerizing with intravenous administration of P12–26. Under such treatment the T cell response to P12–26 was reduced by 80% but there was no enhancement on the responses toward other epitopes. The selection of P12–26 is, thus, unlikely to be due to a competition at the T cell level. It was also found that the dominance of P12–26 was not simply due to a higher affinity of P12–26 for major histocompatibility complex molecules. For example P12–26 binds better to I‐Admolecule than P80–102, but co‐injection with equimole of P12–26 only slightly inhibited P80–102‐induced T cell response. Instead, it required a few molar excess of P12–26 to effectively block the association of P80–102 with I‐Admolecules and to inhibit the T cell immunity to P80–102. Since epitopes such as P46–67, P67–88 and P80–102 were generated from λ repressor cI at a lower molar basis than that of P12–26, it is suggested that the dominance of P12–26 was probably generated by such stoichiometry difference

ISSN:0014-2980    

DOI:10.1002/eji.1830220410

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractFull‐length human retinal cDNA for S antigen (S‐ag) and for the α subunit of transducin (α‐Td) were subcloned into a bacterial expression plasmid vector to generate recombinant fusion proteins with glutathione‐S‐transferase (GST). The recombinant GST‐S‐ag and rGST‐α‐Td fusion proteins were purified from bacterial extracts by continuous flow preparative gel electrophoresis under denaturing conditions, and were assessed for their ability to induce experimental autoimmune uveoretinitis (EAU). Immunization of Lewis rats with single doses of 10 μg‐100 μg rGST‐S‐ag in Freund's complete adjuvant supplemented withBordetella pertussisreadily induced clinical signs of EAU. Immunization with GST alone did not induce EAU indicating that disease activity was ascribable to the S‐ag residues in the fusion protein. Although the α‐Td shares limited sequence homology with S‐ag, the rGST‐α‐Td fusion protein was also not uveitogenic in Lewis rats. The clinical severity of EAU in Lewis rats sensitized with rGST‐S‐ag was found to be milder than that induced with native S‐ag preparations purified from human retina. However, humoral antibody responses to sensitization with the recombinant S‐ag fusion protein were of a higher magnitude than with native S‐ag. The availability of recombinant preparations of human S‐ag protein will be of value in studying its processing and presentation to T cells deri

ISSN:0014-2980    

DOI:10.1002/eji.1830220411

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY