1,721,088 research outputs found
T-cell receptor J-beta gene segment usage in immature and mature human thymocytes
No full textImmature double positive (DP, CD4+CD8+) and mature single positive (SP, CD4+CD8- and CD4-CD8+) human thymocytes from nine thymi were analysed for their complete patterns of relative TCR J beta multigene member usage in relation to six rearranged V beta family exons (V beta 5.1, 6.1-3, 8, 9, 12 and 18). Each sample tested contained mRNA transcripts corresponding to all potential V beta(D beta)J beta combinations. Individual J beta gene segments were expressed in a similar, highly non-random manner both in SP and DP thymocytes, irrespective of original genomic position of the individual associated V beta exon. In addition, ranges of family usage and frequency of individual over-representations of J beta gene segments, as determined in DP and SP thymocyte populations, displayed no significant differences. Upon comparison of DP and SP thymocytes, however, a discrepancy in one aspect of J beta gene utilization was established: decreasing J beta family 1/J beta family 2 ratios were determined to be positively correlated with increasing maturity of thymocytes, a condition further supported by data previously obtained from studies of PBL T cells. At the individual J beta gene level, the observed gradual modification of the relative family usage can largely be explained by a significant shift from a higher J beta 1.1/J beta 2.7 ratio in DP to a higher J beta 2.7/J beta 1.1 ratio in SP thymocytes. Altogether, the present results imply that selectional processes in the thymus appear to have only minor consequences on the distribution pattern of expressed J beta exons. Hence, the disproportionate pattern of TCR J beta gene usage seems to be established mainly at the recombinatorial level followed by minor adjustments during thymic and post-thymic events
Enhanced prevalence of T cell receptor Vbeta7 gene family expression in human intestine-associated T lymphocytes
No full textRelative levels of expression of T cell receptor variable (V) beta and joining (J) beta gene segments were determined in T cells derived from intestinal biopsies of healthy mucosal areas, mesenteric lymph nodes and peripheral blood of the same individuals. Samples taken from patients suffering from inflammatory (n = 8) and non-inflammatory (n = 8) bowel diseases were analyzed by semi-quantitative polymerase chain reaction-based methods. In the intestine, fewer (median = 3.5) V beta gene segments constituted more than 50% of the T cell receptor V beta repertoire compared to that of peripheral blood T cells (median = 7, P < 0.001). Interestingly, in all sixteen individuals studied, intestinal T lymphocytes (IL-T) expressed the V beta 7 gene family to a higher degree than did T cells in the paired peripheral blood and mesenteric lymph nodes (P < 0.001). T cell receptor J beta gene segment analyses of V beta 7+ T cells revealed no significant difference in oligoclonality rates between peripheral blood (4/16) and intestine (7/16) (P = 0.46). Hence, overexpression of intestinal TCR V beta 7 message does not seem to be due to oligoclonal expansions in the majority of the samples
T-cell receptor BJ gene segment expression in human umbilical cord blood CD4 + and CD8 + T-cell subsets
No full textBy employing RT-PCR-based technology, followed by Southern-blot analysis, patterns of relative TRC BJ gene segment usage in human CD4+ and CD8+ umbilical cord blood T cells (UCT) from ten children were determined in relation to seven recombined TCR BV gene (sub) families (BV 3, 5S1, 6S1-3, 8, 9, 12 and 18). Normal frequency of usage of individual BJ members was observed to be extremely nonrandom. BJ usage in association with each BV was ranked and mean ranking values were calculated for individual BJs. Moreover, BJ family usage and family ranges as well as individual BJ over-representations were determined. In all these aspects of BJ exon expression, CD4+ and CD8+ UCT displayed similar distribution patterns. Comparisons of BJ usage in UCT subpopulations and in the adult peripheral blood lymphocyte (PBL) counterparts were performed and many similarities were observed. However, discrepancies in two parameters were recorded; contrary to observations in PBL, individual BJ over-representations were virtually absent in UCT, and significantly less wide BJ family ranges were demonstrated in CD8+ UCT relative to CD8+ PBL T cells. These differences support the notion that UCT are in a less dynamic state than are PBL T cells. Hence, despite the fact that PBL T cells are subjected to continuous antigenic challenge, the striking resemblance of PBL and UCT with regard to the overall individual relative usage, ranking, mean ranking and family utilisation of BJ gene segments, irrespective of the choice of recombined BV exons, may suggest a relatively nondiscriminatory role for the BJ gene product in antigen recognition as compared to those encoded by the BV, (N) and BD gene segments
Enhanced Vbeta7 gene usage by intestinal T-lymphocytes in nondiseased human gut moieties
No full textPeripheral blood T cell expansions in patients with Behcet's disease
No full textBehcet's disease (BD) is a chronic multisystemic inflammatory disorder characterized mainly by recurrent oral and genital aphthous ulcerations and uveitis. Etiology and pathogenesis of BD remain unknown. T cell receptor (TCR) V alpha/V beta gene product expression as well as J beta gene segment expression in peripheral blood of BD patients were analysed to investigate the possible role of T lymphocytes in the etiopathogenesis of BD. Flow cytometry with 12 TCR V-specific MoAbs was used for TCRV analyses. J beta gene segment usage by T cell populations expressing certain V beta s was determined by polymerase chain reaction (PCR) technique with V beta- and C beta-specific primers, Southern blotting of PCR products, and subsequent hybridization with radiolabelled J beta gene segment-specific probes. Although 13 of the 23 BD patients exhibited increases in expression of one or more TCR V-gene products, only expansions among the CD4(+) T cell subset were significantly more frequent in BD patients (7/23) compared with healthy controls (0/15) (P = 0.019). Six out of eight cases followed for up to 20 months had at least one expansion correlated with disease activity. A strict preference for particular J beta gene segments implicating clonality was apparent in all analysed T cell expansions and correlated well with disease activity. These results suggest a possible involvement of antigen-specific T lymphocytes in the pathogenesis of BD
Overexpression of select T cell receptor Vbeta gene families within CD4 + and CD8 + T cell subsets of myasthenia gravis patients: A role for superantigen(s)?
Full text linkBACKGROUND: The principal symptoms of myasthenia gravis (MG), muscle weakness and fatigue due to impaired neuromuscular transmission, are caused by autoantibodies to the muscle nicotinic acetylcholine receptor (AChR). The mechanisms underlying the autoimmune response, however, appear to be initiated by activation of specific HLA class II-restricted CD4+ T lymphocytes. Thus, central to elucidating the causation of MG is determining how T cells are recruited to contribute to misguided immunological assaults on the major autoantigenic target, AChR. MATERIALS AND METHODS: By combining a polymerase chain reaction (PCR)-based strategy and Southern blot technique, we have analyzed the frequency of expression of 22 individual T cell receptor (TCR) V beta gene subfamilies in CD4+ and CD8+ peripheral blood T cell subsets derived from eight MG patients and seven healthy controls. The quantification of relative usage of individual TCR J beta gene segments was performed by hybridization of PCR-amplified products (specifically V beta 1-C beta) with a complete panel of 32P-5'-end-labeled J beta-specific oligonucleotide probes, followed by scanning analysis of autoradiographs. RESULTS: Comparisons of data obtained from V beta analyses of T cells from MG patients with those from healthy individuals established that MG patients significantly overexpressed V beta 1, V beta 13.2, V beta 17, and V beta 20 gene family members within both CD4+ and CD8+ T cell subpopulations. Moreover, analysis of the relative utilization of individual TCR J beta gene segments in V beta 1+/CD4+ and V beta 1+/CD8+ T lymphocytes revealed distribution patterns in patients indistinguishable from those recorded in the corresponding cell subsets derived from controls. CONCLUSIONS: T lymphocytes from MG patients displayed a biased overexpression of four TCR V beta gene segments: V beta 1, V beta 13.2, V beta 17, and V beta 20. The relative frequencies of association of individual V beta 1 (D beta) J beta combinations revealed that J beta gene usage in the V beta 1-over-represented T cell subsets had normal distribution patterns. It can thus be deduced that J beta gene segment products appear not to have a selective effect on the process leading to overexpression of V beta 1 exons in MG patients. Hence, our observations suggest a possible role for superantigen(s) in the T cell activation in MG patients
HIV infection leads to differential expression of T-cell receptor V-beta genes in CD4+ and CD8+ T cells
No full textObjective: To analyse variation in T-cell receptor (TCR) Vbeta gene expression in T cells in HIV-infected individuals.
Design: Because there are very few monoclonal antibodies available for studying TCR Vbeta gene expression, we used polymerase chain reaction (PCR) to analyse the TCR Vbeta repertoire in HIV-infected individuals using specific primers for 20 distinct families of TCR Vbeta.
Methods: Evaluation of TCR Vbeta gene expression in peripheral blood from HIV-1-infected individuals [two in Centers for Disease Control (CDC) stage II, five in CDC stage III and four in CDC stage IV]. Complementary DNA was produced from CD4+ and CD8+ T cells, amplified by PCR and analysed after Southern blotting and hybridization with a Cbeta-specific oligonucleotide probe.
Results: Vbeta gene expression was dramatically modified, especially in AIDS patients. The CD4+ T-cell subset showed both overexpression (Vbeta2) and deletions or underexpression (Vbeta9-Vbeta20), whereas these gene segments were expressed normally in the CD8+ subset. Only Vbeta 3 was deleted or underexpression in both CD4+ and CD8+ populations in AIDS patients.
Conclusions: HIV-1 infection induces CD4+ T-cell deficiency, both in total numbers and by causing a paucity of select Vbeta gene expression in this subset. In addition, the Vbeta3 gene family was deleted or underexpressed was observed in both CD4+ and CD8+ T-cell subsets from patients in CDC stage IV. These results are compatible with changes in Vbeta gene expression known to occur under the action of endogenous or exogenous superantigens
Natural specific T cell immunity in patients with B-cell chronic lymphocytic leukaemia (B-CLL) : a clinical and immunological study
No full textAnalysis of TCRBV (T-cell receptor B variable) gene usage of the T cell repertoire in patients with B cell chronic lymphocytic leukaemia (B-CLL) and age-matched healthy control donors showed that major perturbations were more frequently seen in the CD4+ T cell subset than in CD8 population. Analysis of the CDR3 length polymorphism revealed a significantly higher degree of clonality within the CD4+ and CD8+ T cell repertoire of patients as compared to the normal control population. These results suggest that non-malignant CD4+ T cells as well as CD8+ T cells may be involved in the pathogenesis of B-CLL.CLL patients showed the presence of a naturally occurring CD4 and CD8 T cell specifically recognizing the leukaemic B cells. Analyses of cytokines by realtime RT-PCR revealed that Thl cytokines were the most frequently observed cytokines expressed by T cells recognizing the autologous tumor B cells. Upregulation of CD80 on the leukaemic B cells was necessary for induction of the specific T cell response. The T cell response was either MHC class I- or class II-restricted.Analyses of TCR BV gene usage of tumor-restricted T cells showed overexpression 'of certain BVs in CD4 and CD8 T cells as compared to native T cells. Furthermore, analysis of the CDR3 length polymorphism showed that over-expressed BVs shifted from mostly a polyclonal pattern to an oligoclonal/monoclonal pattern after stimulation of T cells with the autologous tumor B cells.Dendritic cells (DC) were generated in vitro from blood CD14+ cells. Most of the DC exhibited a mature phenotype indicated by CD83 and MHC class II expression, as well as by morphology. CLL DC had a similar expression of accessory molecules as control DC. However the pattern of cytokines was different in CLL as compared to control DC. DC of CLL patients had a similar capacity to present antigen as control DC.A VH-CDR3 specific T cell response was demonstrated in CLL patients both by proliferation assay and by IFN-gamma production. The T cell specific response could be inhibited by monoclonal antibodies against MHC class Il or MHC class I molecules.In summary, in B-CLL patients a natural specific T cell response can be demonstrated. However, the biological significance of such a tumor specific immunity remains to be established. The occurrence of leukaemia specific T cells suggests that CLL might a candidate for developing a therapeutic vaccine approach.List of scientific papersI. Rezvany MR, Jeddi-Tehrani M, Osterborg A, Kimby E, Wigzell H, Mellstedt H (1999). "Oligoclonal TCRBV gene usage in B-cell chronic lymphocytic leukemia: major perturbations are preferentially seen within the CD4 T-cell subset. " Blood 94(3): 1063-9 https://pubmed.ncbi.nlm.nih.gov/10419899II. Rezvany MR, Jeddi-Tehrani M, Rabbani H, Lewin N, Avila-Carino J, Osterborg A, Wigzell H, Mellstedt H (2000). "Autologous T lymphocytes may specifically recognize leukaemic B cells in patients with chronic lymphocytic leukaemia. " Br J Haematol 111(2): 608-17 https://pubmed.ncbi.nlm.nih.gov/11122109III. Rezvany MR, Jeddi-Tehrani M, Wigzell H, Osterberg A, Mellstedt H (2001). "Leukaemia specific monoclonal/oligoclonal TCR-BV usage in patients with chronic lymphocytic leukaemia" (Submitted)IV. Rezvany MR, Jeddi-Tehrani M, Biberfeld P, Soderlund J, Mellstedt H, Osterberg A, Rabbani H (2001). "Dendritic cells in patients with non-progressive B-CLL have a normal functional capability but abnormal cytokine pattern." Br J Haematol (In Print)V. Rezvany MR, Jeddi-Tehrani M, Rabbani H, Ruden U, Hammarstrom L, Osterborg A, Wigzell H, Mellstedt H (2000). "Autologous T lymphocytes recognize the tumour-derived immunoglobulin VH-CDR3 region in patients with B-cell chronic lymphocytic leukaemia. " Br J Haematol 111(1): 230-8 https://pubmed.ncbi.nlm.nih.gov/11091206</p
Ligation of human Fc receptor like-2 (FCRL2) by monoclonal antibodies downregulates B cell receptor mediated signaling
No full textB-cell antigen receptor (BCR) signalling and its regulation through negative and positive regulators are critical for balancing B-cell response and function. Human Fc receptor like-2 (FCRL2), a member of the newly identified FCRL family, could influence B-cell signalling due to possession of both immunoreceptor tyrosine-based activation and inhibitory motifs (ITAM and ITIM). Since the natural ligand of FCRL2 has not been identified, we generated FCRL2-specific monoclonal antibodies (mAbs) and employed them to investigate the influence of FCRL2 stimulation on BCR signalling in an FCRL2-expressing B-cell line. Two anti-FCRL2 mAb-producing hybridoma clones (5A7-E7 and 3D8-G8) were selected. None of the mAbs displayed any cross-reactivity with the other members of the FCRL family including recombinant FCRL1, -3, -4 and -5, as tested by FACS and ELISA techniques. Engagement of the FCRL2 by these mAbs resulted in significant inhibition of BCR signalling mediators such as calcium mobilization and phosphorylation of the mitogen-activated protein kinases Erk, p38 and Jnk. These findings indicate that the FCRL2 ITIM motifs are functional and the anti-FCRL2 mAbs may mimic the natural ligand of FCRL2 by induction of inhibitory signals in B cells
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