Distinct patterns of conservation of exons and introns of T-cell receptor beta chain constant region genes in subspecies of Mus.
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Biomedical subjects
Publications and source records attributed to T J Kindt.
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Transformation of peripheral blood lymphocytes by co-incubation with EBV produces B lymphoblastoid cell lines, but rearrangement of TCR beta-chain genes was observed in three different cell lines derived from two individuals. Because rearrangement of TCR genes in B lymphocytes is considered a rare event, these B lymphoblastoid cell lines with rearranged TCR beta-genes were examined in detail to determine whether there were any additional characteristics to distinguish them from B lymphoblastoid cell lines with germ-line TCR beta-genes. All B lymphoblastoid cell lines contained rearranged Ig H and kappa L chain genes, secreted Ig, and expressed B and not T cell surface markers. Cell lines with rearranged TCR beta-genes had rearranged both IgH genes and had rearranged and subsequently deleted both kappa C region genes. Furthermore all three B lymphoblastoid cell lines with rearranged TCR beta-genes produced small amounts of Ig with lambda-L chains. Although the cellular mechanisms maintaining lineage-specific rearrangement events remain unknown, extensive Ig gene rearrangement and inefficient Ig production by B cells may be indicators of a cellular status where normally stringent lineage-specific control elements fail to function efficiently.
A gene encoding the lambda 5 light chain constant region was isolated from a genomic library from the SPE mouse strain (C lambda 5S). SPE is an inbred wild mouse strain belonging to the Mus 3 or Mus spretus group that has been genetically isolated from Mus 1 (the group to which laboratory mice belong) for a period of 1-3 million years. The sequence of the C lambda 5S gene shows strong homology to C lambda 5 of (C57BL/6J x DBA/2)F1 both in the coding region (98% identity) and in the 5'- and 3'-flanking regions (98 and 95% identity, respectively). Sequence comparison of C lambda 5 genes with C lambda 1 of BALB/c shows only few substitutions in the C lambda 5 coding regions and suggests that the three genes have a common ancestor. These data indicate that the C lambda 5 gene has evolved under strong selective pressure and probably encodes a functional gene product. The conservation of the C lambda 5 gene in various Mus species was observed by high stringency Southern blot analyses using a C lambda 5S probe on DNA sample from members of four different groups of wild mice. All the laboratory and wild mouse strains tested, including those with amplified sets of C lambda 1 and C lambda 2 hybridizing sequences, showed only single C lambda 5 hybridizing fragments. Little variation in size of restriction fragments detected with the C lambda 5 probe was seen in the different Mus species suggesting a high degree of conservation.(ABSTRACT TRUNCATED AT 250 WORDS)
We report the successful infection of two rabbit T-cell lines and one rabbit macrophage line with human immunodeficiency virus 1 (HIV-1). One T-cell line was a herpesvirus ateles transformant, the other T-cell line was a human T-cell leukemia virus I transformant, and the macrophage line was a simian virus 40 transformant. After infection with a high-titered HIV-1 stock, the rabbit cultures exhibited properties that closely mimic those of HIV-1-infected human cells. Productive infection was evident in cultures 7-14 days after infection, as shown by an increase in reverse transcriptase activity, a concomitant increase in positive cells detected by indirect immunofluorescence using serum from a patient with acquired immunodeficiency syndrome, and a decrease in cell viability. RNA gel blot hybridization and protein immunoblot analyses of infected cells indicated that all predicted viral transcripts and proteins were synthesized during the course of the infection. Proof that cell-free culture supernatants of the infected rabbit cell lines contained infectious virus was given by successful passage onto a susceptible human T-cell line. The ability of HIV-1 to infect transformed rabbit cell lines in vitro suggests that, with appropriate manipulation, the rabbit may provide a model for infection with HIV-1.
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The class I gene family of the rabbit consists of 8 to 12 members and includes a gene that is transcribed only in T cells and in lymphoid tissues containing T cells. A cDNA clone, pR27, was isolated from a cDNA library constructed using mRNA from the T cell line RL-5. The pR27 insert was 1.9 kb long and included sequences that correspond to class I exons 2, 3, and 4 encoding external domains. Intron 4 sequence was found downstream followed by an unusually long 3' region which contained a sequence highly repeated in the rabbit genome. Although the pR27 exons encode structures typical of class I antigens, structural comparisons show no close relationship to other rabbit class I genes in the 3' regions, and no relationship to the 3' region of any murine gene including those encoded in the T1a region. By contrast, similarity of the 3' sequence has been found with human genes of the HLA-A type both by sequence comparison and by DNA hybridization studies. Southern blot analyses with a specific probe from this clone indicated that the gene encoding pR27 is present as a single copy in all rabbit DNA samples examined. Northern blot analysis and S1 nuclease mapping studies revealed that transcripts corresponding to pR27 are present in virally transformed T cell lines, thymus, and, to a lesser extent, in spleen and appendix but not in nonlymphoid tissue. The sizes of the detected transcripts (2.8 and 3.9 kb) were larger than that normally observed for a class I gene.
Genomic clones corresponding to five distinct major histocompatibility complex class II alpha-chains have been described for the rabbit; four of these encode complete, potentially functional alpha-chains. Hybridization analysis and preliminary sequence analysis indicate that one of these clones is structurally related to HLA-DP alpha, one to -DR alpha, one to -DQ alpha and one to -DZ alpha. Probes specific for the four class II genes were used to screen RNA samples from normal rabbit tissues to determine which of these genes are transcribed and whether expression of any particular gene is tissue specific. All four of the genes are transcribed, but there are variations in the levels of expression, in tissue distribution, and in transcript size. The highest levels of RLA-DR alpha, -DQ alpha, and -DP alpha transcription were found in lymphoid tissues. Lower levels of transcription were also detectable in several nonlymphoid tissues. Transcripts observed were about 1.3 kb, a size expected for these class II alpha-chain genes based on experience with their human homologues. The RLA-DZ alpha probe corresponding to HLA-DZ alpha hybridized weakly with a band of 3.6 kb; its expression could be detected only in lymphoid tissues. The size of the DZ alpha transcript, its tissue distribution, and partial sequence data confirm its homology with the human gene DZ alpha. In blots of total cellular RNA, a probe for a recently described human beta-chain, DO beta, hybridized to a transcript of about 1.3 kb in lymphoid tissues. These data indicate that RNA transcripts corresponding to all HLA class II loci described to date can be detected in rabbit tissues.
A genomic clone containing the lambda constant (C) region genes (C lambda 2S and C lambda 4S) has been isolated from a genomic library from the mouse strain SPE. SPE is an inbred strain derived from progenitors trapped near Grenada in Spain and has been classified as mus 3 or mus spretus. The sequence of the C lambda 2S gene is virtually identical to that of BALB/c both in the coding region and in flanking sequences, suggesting that it is an expressed gene in the SPE strain. By contrast, the C lambda 4S gene on the same cluster has diverged in sequence from that of BALB/c and contains a large deletion that precludes its normal expression. Whereas BALB/c J lambda 4 region contains substitutions that probably preclude its usage, the SPE J lambda 4 gene includes all sequences required for a functional J gene. Comparison of the C lambda 2S and C lambda 4S gene sequences with those available for BALB/c C lambda 3 and C lambda 1 confirms the close relationship between the C lambda 1-C lambda 4 and C lambda 2-C lambda 3 gene pairs. The C lambda 3 gene of BALB/c is more closely related to C lambda 2S than is C lambda 1 of BALB/c to C lambda 4S. If it is assumed that C lambda 1 and C lambda 2 are respective duplicates of C lambda 4 and C lambda 3 and that these duplications occurred at the same time, then the C lambda 2 gene has been under stronger selective pressure than C lambda 4.
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The human HLA-DQ alpha probe was used to screen genomic and cDNA libraries constructed from a rabbit T-cell line. Clones containing highly homologous sequences were obtained from both libraries and their sequences were determined. The organization of the RLA-DQ gene was determined by comparison of the nucleotide sequences of the genomic clone to that of the corresponding cDNA clone. This analysis allowed assignment of the complete structure of the RLA-DQ alpha chain. Comparisons with human and mouse class II products revealed that RLA-DQ is more closely related to HLA-DQ/DX than to H-2A. In contrast to the DQ/DX region of man, which contains at least two distinct alpha genes, the rabbit genome contains a single DQ gene which is equally distant from the HLA-DQ or -DX genes. The rabbit DQ alpha gene, like human HLA-DQ, is transcribed in T cells.
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Partial N-terminal amino acid sequence analyses were performed on rabbit MHC class II molecules eluted from 2-D electrophoretic gels. Rabbit spleen cells were biosynthetically labelled with 3H-phenylalanine, 3H-tyrosine and 35S-methionine and class II molecules were immunoprecipitated with a monoclonal antibody, 2C4. The immunoprecipitates were electrophoresed on 2-D gels and as many as 15 spots were observed. Individual spots corresponding to alpha and beta chains were eluted from unfixed gels following visualization of the spots by autoradiography of 35S-Met labelled polypeptides. Ten eluted polypeptides were subjected to amino acid sequence analysis to locate Phe and Tyr residues. Comparison of these partial sequences with sequences of human class II molecules indicated that each of six beta chains and three of four alpha chains were homologous to human DQ molecules; one of the alpha chains appeared homologous to DR alpha or DP alpha. The assignment of alpha or beta chain to the polypeptides was confirmed by radiosequence of molecules labelled with 35S-Cys residues. Thus, by a relatively simple procedure, individual MHC class II polypeptides in spleen cell lysates have been separated from each other and partial amino acid sequences have been obtained.
Monoclonal antibodies were prepared against synthetic peptides synthetized on the basis of nucleotide sequence from cDNA and genomic clones encoding a class I antigen expressed by the rabbit RL-5 cell line. Using a peptide corresponding to positions 61-73 of the N domain, we were able to obtain an hybridoma producing monoclonal antibody which recognized the peptide as well as the native class I antigen. This hybridoma, designated anti-61, reacted with cell surface molecules on RL-5 cells and on human HeLa cells transfected with the 19-1 gene encoding RL-5 class I antigen. No reactivity with HeLa cells prior to transfection could be detected by radioimmunoassay or by fluorescent activated cell sorter analyses, although these cells were strongly positive in both assays with anti-human class I reagents. Antibody reaction to positive cells could be inhibited by the homologous peptide but not by unrelated peptides. Anti-61 antibody precipitated a 41,000 mol. wt molecule from RL-5 cells with an N-terminal amino acid sequence corresponding to the RL-5 class I antigen.
Genetic analyses of the human T-cell receptor (TCR) alpha-chain genes indicate that recombination events may occur frequently within this gene complex. Examination of the inheritance of restriction fragment length polymorphisms (RFLP) detected by using probes for constant or variable region gene segments made it possible to assign TCR alpha haplotypes to the 16 parents and 43 offspring of eight families studied. A total of six RFLP, three for the constant region and three for variable region gene segments, were examined in the present studies. Most enzyme and probe combinations tested revealed no polymorphism and those finally selected for the study showed limited polymorphism in that only two or, in one case, three allelic forms of the gene were seen. In spite of limited variability at this level, extensive heterogeneity was observed for the combinations of markers present in haplotypes, suggesting that frequent recombination events have occurred. Most strikingly, multiple combinations of RFLP occurring in close proximity of the TCR alpha constant region gene were observed in this study. A high recombination frequency for the TCR alpha gene complex is further supported by the observation that two children, one in each of two families, inherited recombinant TCR alpha haplotypes.
Studies of murine T cell receptor genes indicate that the VT beta repertoire, in contrast to the large VT alpha, VH, and VK repertoires, is limited to approximately 21 genes. Large differences between the various VT beta sequences allow classification into distinct subfamilies consisting of one or few members. The VT beta sequence of a gene, RTB92, expressed in a rabbit T cell line is most closely related to a VT beta gene expressed in the human cell line Molt-4. Genomic blots with RTB92 VT beta region used as probe indicated conservation of related VT beta gene subfamilies in man and pig, but no related sequences were seen in rat, mouse, or hamster. The relationship among these VT beta genes mirrors similarities and differences in MHC genes of the compared species and suggests coordinate evolution of these functionally related gene families. The constant region of RTB92 was shown to be rabbit CT beta 2 by reference to genomic clones. Comparisons with constant region sequences of human and murine CT beta 1 and CT beta 2 chains reveal no similarities in amino acid or nucleic acid sequence in the coding region characteristic of the respective isotypes. Intraspecies homologies between CT beta 1 and CT beta 2 sequences were much greater than those between CT beta 1 or CT beta 2 from other species. By contrast, comparisons of JT beta and 3' untranslated region sequences showed significant interspecies conservation of sequences in the beta 1 and in the beta 2 regions.
Continuous rabbit macrophage-like cell lines were established after in vitro infection of spleen cells with either Simian virus 40, lymphotropic papovavirus or herpesvirus sylvilagus. These cell lines are characterized as morphologically similar to mature macrophages, esterase positive, and have unrearranged immunoglobulin genes. They possess macrophage functionality because they are highly phagocytic and are able to mediate an antibody dependent cell mediated cytotoxicity assay on chicken red blood cells. Northern blot analysis of total cellular RNA with a DQ alpha probe indicates that the cell lines constitutively express message for class II gene products. In addition, cell sorter analysis indicates that two of these lines display class II antigen at the cell surface.