Sequences and repertoire of the human T cell receptor alpha and beta chain variable region genes in thymocytes

To compare and contrast the human T cell antigen receptor (TcR) alpha and beta chain messages found in human thymocytes to those previously isolated from human peripheral blood T lymphocytes and other nonthymic sources, 13 TcR alpha and 13 TcR beta cDNA were isolated from a human thymocyte library and the nucleotide sequences were determined. The data indicate that, as was found in the peripheral T lymphocytes, the majority of the TcR alpha and TcR beta chain thymocyte cDNA were derived from potentially functional messages. Although the thymocyte-derived TcR cDNA do not contain any unique structural features when compared to TcR cDNA from mature T lymphocytes, 4 new J alpha segments, 17 new V-gene segments (9 V alpha; 8 V beta) and 7 additional V-gene families (4 V alpha and 3 V beta) and sequences had been identified. The exon C beta O, found in many murine thymocyte TcR beta messages, was not found in over 75 human beta chain messages. Based on these new data, a revised estimate of human TcR V alpha, J alpha and V beta repertoires is calculated. The most significant change has been the increase in the estimated number of human TcR V beta-gene segments to a total of about 100 distributed among about 18 families. The V alpha families are now revised upward to 16, with a total number of V alpha segments of 50. The estimate of the J alpha segments in humans remains between 50-100.     

Polymorphism of the human T cell receptor alpha chain variable genes: identification of a highly polymorphic V gene probe

In this study, we report the RFLP of the human T cell receptor (TCR) alpha chain variable gene segments. Using DNA samples from 20 individuals and three restriction endonucleases (BamHI, EcoRI and HindIII), the degree of RFLP of a number of different V gene segments was defined. Half of the V alpha subfamilies (6/12) were characterized by a predominant hybridization pattern, with only a few individuals displaying a second pattern. However, one particular V gene family, V alpha 6, has at least five allelic forms that segregated consistently in familial studies. The V alpha polymorphisms revealed in this study, together with those exhibited by V beta gene subfamilies, should prove useful in studying possible associations between TCR gene usage and disorders of the immune system.     

The human T cell receptor alpha variable (TRAV) genes

'Human T Cell Receptor Alpha Variable (TRAV) Genes', the eighth report of the 'IMGT Locus in Focus' section, comprises four tables: (1) 'Number of human germline TRAV genes at 14q11 and potential repertoire'; (2) 'Human germline TRAV genes at 14q11'; (3) 'Human TRAV allele table', and (4) 'Correspondence between the different human TRAV gene nomenclatures'. These tables are available at the IMGT Marie-Paule page of IMGT, the international ImMunoGeneTics database (http://imgt.cines.fr:8104) created by Marie-Paule Lefranc, Université Montpellier II, CNRS, France.     

Involvement of both T cell receptor V alpha and V beta variable region domains and alpha chain junctional region in viral antigen recognition.

We have studied the lymphocytic choriomeningitis virus (LCMV)-specific cytotoxic T cell response in transgenic mice expressing either the T cell receptor (TcR) alpha (V alpha 2/J alpha TA31) or the corresponding TcR beta (V beta 8.1/D beta/J beta 2.4) chain originally isolated from the LCMV glycoprotein specific (residues 32-42), H-2Db-restricted T cell clone P14. The expression of single transgenic TcR chains did not influence the corresponding endogenous TcR V gene usage in unstimulated T cells indicating that one particular TcR alpha or beta chain can randomly pair with different V beta or V alpha chains without any obvious bias. However, upon infection with LCMV, reactive cytotoxic T lymphocytes (CTL) from P14 beta-transgenic mice were predominantly V alpha 2+ whereas CTL from P14 alpha-transgenic mice preferentially expressed V beta 8.1 and unexpectedly also V beta 8.3 (but not V beta 8.2). Correspondingly, the LCMV-specific CTL response in both alpha and beta TcR-transgenic mice was strongly biased to the original P14 T cell epitope (LCMV glycoprotein residues 32-42). Sequence analysis of a large panel of LCMV-reactive "half-transgenic" TcR from P14 single receptor chain-transgenic mice revealed a highly conserved VJ alpha and a more diverse VDJ beta junctional region. This report demonstrates that the antigen specificity of the studied TcR depends on the specific combination of both TcR alpha and beta chains which implies that amino acids located in the TcR V alpha and V beta segments as well as in the junctional region are involved in binding of the viral antigenic fragment.     

The human T cell receptor beta variable (TRBV) genes

'Human T Cell Receptor Beta Variable (TRBV) Genes', the seventh report of the 'IMGT Locus on Focus' section, comprises four tables: (1) 'Number of human germline TRBV genes at 7q35 and potential repertoire'; (2) 'Human germline TRBV genes at 7q35'; (3) 'Human TRBV orphons on chromosome 9 (9p21)', and (4) 'Human TRBV allele table'. These tables are available at the IMGT Marie-Paule page from IMGT, the international ImMunoGeneTics database (http://imgt.cines. fr: 8104) created by Marie-Paule Lefranc, Université Montpellier II, CNRS, France.     

The human T cell receptor alpha joining (TRAJ) genes

'Human T cell Receptor Alpha Joining Genes', the 9th report of the 'IMGT Locus in Focus' section, comprises 3 tables: (1) 'Human germline TRAJ genes'; (2) 'Human TRAJ allele table'; and (3) 'Nucleotide and protein displays of the human TRAJ alleles (overview)'. These tables are available on the IMGT Marie-Paule page from IMGT, the international ImMunoGeneTics database (http://imgt. cines.fr:8104) created in 1989 by Marie-Paule Lefranc, Université Montpellier II, CNRS, France.     

Structure and organization of the T cell receptor alpha chain genes in Atlantic salmon

A cDNA fragment of the T cell receptor (TCR) alpha chain mRNA in Atlantic salmon (Salmo salar) was amplified by PCR and used as a probe to isolate a full-length clone from a leukocyte cDNA library. Additionally, a genomic lambda clone comprising the TCR alpha chain constant region (Calpha) gene and flanking regions was isolated and partially sequenced. The Calpha gene consists of three exons corresponding to the immunoglobulin (Ig) domain, the hinge region and the transmembrane peptide/cytoplasmatic tail, and two exons corresponding to the untranslated tail of the mRNA. Remnants of a transposase gene and a partial duplication of the Calpha gene were found nearby the intact gene. One J segment was found 1.5kb upstream of the Calpha gene. Twenty-six other J elements were identified among cDNA fragments covering the V/J/Calpha junction. Representatives of five Valpha gene families were identified by PCR amplification of genomic DNA fragments. PCR amplification of Calpha fragments from another individual revealed a slightly different Calpha gene which most likely represents an allelic variant.     

The human T cell receptor alpha-delta locus: a physical map of the variable, joining and constant region genes

In this study a physical macro-restriction map of the entire human alpha locus that spans about 1000 kilobase pairs and includes the V alpha, J alpha and C alpha genes is presented. Evidence is provided that gene duplications were involved in the increase of genomic diversity of V alpha genes. In addition, we show a detailed map of a 40-kb region located approximately 100 kg upstream of the human C alpha gene. Direct evidence is provided to support that the human alpha chain locus, like the murine, also contains another T cell constant region gene in the alpha chain locus, the human delta chain gene. In addition, two J segments and one D segment have been identified. Using these genomic probes, we show that several T cell lines, including those known to express the surface gamma/delta heterodimer, have rearranged this region. The design of two separate centers of rearrangement within one locus that are involved in rearrangement events at different times, and the presence of high number of J segments in this region, may render the locus highly vulnerable to chromosomal translocation during T cell development.     

Two distinct immunogenic epitopes on the alpha chain of human T cell antigen receptor

Monoclonal antibodies (MAb) to human T Cell Antigen Receptor (TCR) have been used to study the structure and function of TCR. Using purified alpha/beta heterodimeric protein, we have generated two MAb against human TCR alpha protein. The two MAb, alpha F1 and alpha F2, recognized amino acid residues 141-159 and 212-231 of the constant region of the alpha chain TCR. Although neither MAb reacted with viable T cells, both antibodies immunoprecipitated TCR alpha/beta heterodimer from HPB-ALL, Jurkat, PBL and a 32 kDa in vitro translation product of alpha chain cDNA. These antibodies have been shown to be useful in the immunohistochemical staining of human tissues. These two MAb, together with other anti-framwork MAb to TCR, should provide valuable reagents in the study of TCR and clinical classification of T cell lineage neoplasms.     

Surface expression of the T cell receptor complex requires charged residues within the alpha chain transmembrane region

The T cell receptor (TcR) complex is a multi-subunit glycoprotein comprising at least five transmembrane polypeptides. An unusual characteristic of each of the transbilayer domains is the presence of charged amino acids. To examine the importance of these residues for the association and consequent surface expression of the components of the complex, a TcR alpha chain containing either charged or neutral residues within its transbilayer segment was introduced into the human T cell line MOLT-4, and the appearance of the TcR complex at the cell surface was assayed. Surface expression was observed only in MOLT-4 cells transfected with the alpha chain containing charged transbilayer residues. Thus, these residues most probably play a crucial role in the assembly process.     

Regulation of T cell antigen receptor alpha chain gene expression]

A T cell antigen receptor (TcR) gene is considered to be a model system for studies of developmentally-regulated, lineage-specific gene expression. For the TcR alpha gene expression, it has been shown that the enhancer region located at 3.0 kb in mouse or 4.5 kb in human downstream of TcR C alpha gene is essential. The enchancer is demonstrated to contain at least four nuclear protein binding sites called T alpha 1-T alpha 4. In this report, we analysed the molecular requirement for murine TcR alpha gene enhancer function by using in vitro mutagenesis system and CAT assay, and obtained the following results: 1. The T alpha 2 element, especially ACATCC sequence, is important for enhancer activity, because the mutation in the sequence completely abolished the activity. 2. The sequence TCTGG near by the ACATCC sequence seems also important for the enhancer function, since the mutation lost the half of the activity. 3. The ets1, which is known to bind the ACATCC site, upregulates the enhancer activity of the reporter gene containing the concatemers of T alpha 2 region. The results indicate that ets1 has a trans-activating activity to the T alpha 2 region of TcR alpha chain enhancer.     

Inhibition of superantigen recognition by peptides of the variable region of the T cell receptor beta chain.

T cells bearing certain variable (V) regions of the T cell receptor (TcR), including V beta 3, V beta 6, V beta 8.1 and V beta 9, 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-V beta region and Mls-1a, we examined the effect of peptides derived from the protein sequence of V beta 6 on recognition of Mls-1a by 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 V beta 6 peptide sequence interfere with the activation of several V beta 6+ hybridomas by Mls-1a-bearing spleen cells, but not with that of a V beta 8+ hybridoma. The Mls-reactive hybridomas are specific for a synthetic peptide poly-18, poly EYK(EYA)5 and 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)5 by the same V beta 6+ 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-1a is 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 induction and regulation of immune responses.     

人类TCRαβ家族V基因的进化研究

目的：了解人类TCRα家族V基因（TCRAV）和TCRβ家族V基因（TCRBV）的进化特征。方法：采用MEGA3．1软件对人类TCRAV和TCRBV基因分别构建进化树，并估算基因复制的发生时间；采用FEL法检测TCRAV和TCRBV编码序列正选择和负选择位点。结果：进化树显示TCRAV和TCRBV的基因分组在进化过程中已经维持了相当长的时间。TCRAV已经不受正选择作用，TCRBV基因序列的CDR8区域检测到两个正选择位点。结论：人类TCRαβ家族V基因的进化特征为研究TCR基因在机体免疫及疾病防治提供了理论分析基础。