Isotypic exclusion of gamma delta T cell receptors in transgenic mice bearing a rearranged beta-chain gene

The rearrangement of T cell antigen receptor beta- and gamma-chain gene segments was studied in transgenic mice that bear a functional beta-chain gene. Virtually all CD3-positive T cells derived from transgenic mice express beta chains containing the transgene-encoded V beta 8.2 variable region on their surfaces and do not express endogenous beta-chain variable regions. Expression of endogenous V beta genes is inhibited at the level of somatic recombination during thymic ontogeny. Furthermore, rearrangements of the TCR gamma-chain genes are also markedly inhibited in these transgenic animals. Hence expression of the TCR beta transgene has led to allelic exclusion of alpha beta receptors and isotypic exclusion of gamma delta T cell receptors.     

Structure and diversity of the human T-cell receptor beta-chain variable region genes

In order to characterize the variability of the expressed human T-cell receptor (TCR) beta-chain repertoire and contrast this variability to the known murine beta-chain repertoire, 15 independent complementary DNA (cDNA) clones containing TCR beta-chain variable region (V beta) genes were isolated from a human tonsil cDNA library. The nucleotide and derived amino acid sequences of these 15 V beta genes were analyzed together with 7 previously defined sequences. Fifteen different human V beta genes could be identified from 22 independent sequences. By means of DNA hybridization and sequence homology comparisons, it was possible to group these 15 genes into ten distinct V beta subfamilies, each containing from one to seven members. Minimal polymorphism was noted between individuals, except in multimember subfamilies. The amino acid sequences of these genes contain conserved amino acids that are also shared by murine TCR V beta genes and immunoglobulins; no features were found that distinguish human V beta genes from their murine counterparts. Evaluation of secondary structure showed that maximum variability coincides with generally hydrophilic portions of the amino acid sequence, while specific hydrophobic regions were conserved in all V beta genes examined.     

Measuring the human T cell receptor gamma-chain locus

The human T cell receptor gamma locus, including eleven variable-region, five joining-region, and two constant-region segments, is contained in 160 kilobases. During T cell somatic development these genes undergo rearrangement by deletion of the sequences separating the variable and joining regions. The molecular map of this locus was completely defined by deletion mapping and restriction mapping. Restriction fragments were resolved by standard agarose electrophoresis and field inversion electrophoresis. These studies demonstrate that the deletions in this locus, which occur during the formation of a functional T cell receptor gamma-chain gene, range from 50 to 145 kilobases in length. These studies also provide a structural basis for understanding the development of the gamma-chain peptide repertoire, and extends the potential of the emerging pulsed-field electrophoretic technology.     

Polymerase chain reaction with single-sided specificity: analysis of T cell receptor delta chain

In the polymerase chain reaction (PCR), two specific oligonucleotide primers are used to amplify the sequences between them. However, this technique is not suitable for amplifying genes that encode molecules where the 5' portion of the sequences of interest is not known, such as the T cell receptor (TCR) or immunoglobulins. Because of this limitation, a novel technique, anchored polymerase chain reaction (A-PCR), was devised that requires sequence specificity only on the 3' end of the target fragment. It was used to analyze TCR delta chain mRNA's from human peripheral blood gamma delta T cells. Most of these cells had a V delta gene segment not previously described (V delta 3), and the delta chain junctional sequences formed a discrete subpopulation compared with those previously reported.     

Immunochemical proof that a novel rearranging gene encodes the T cell receptor delta subunit

The T cell receptor (TCR) delta protein is expressed as part of a heterodimer with TCR gamma, in association with the CD3 polypeptides on a subset of functional peripheral blood T lymphocytes, thymocytes, and certain leukemic T cell lines. A monoclonal antibody directed against TCR delta was produced that binds specifically to the surface of several TCR gamma delta cell lines and immunoprecipitates the TCR gamma delta as a heterodimer from Triton X-100 detergent lysates and also immunoprecipitates the TCR delta subunit alone after chain separation. A candidate human TCR delta complementary DNA clone (IDP2 O-240/38), reported in a companion paper, was isolated by the subtractive library approach from a TCR gamma delta cell line. This complementary DNA clone was used to direct the synthesis of a polypeptide that is specifically recognized by the monoclonal antibody to TCR delta. This complementary DNA clone thus corresponds to the gene that encodes the TCR delta subunit.     

Structure and specificity of a class II MHC alloreactive gamma delta T cell receptor heterodimer

Two distinct CD3-associated T cell receptors (TCR alpha beta and TCR gamma delta) are expressed in a mutually exclusive fashion on separate subsets of T lymphocytes. While the specificity of the TCR alpha beta repertoire for major histocompatibility complex (MHC) antigens is well established, the diversity of expressed gamma delta receptors and the ligands they recognize are less well understood. An alloreactive CD3+CD4-CD8- T cell line specific for murine class II MHC (Ia) antigens encoded in the I-E subregion of the H-2 gene complex was identified, and the primary structure of its gamma delta receptor heterodimer was characterized. In contrast to a TCR alpha beta-expressing alloreactive T cell line selected for similar specificity, the TCR gamma delta line displayed broad cross-reactivity for multiple distinct I-E-encoded allogeneic Ia molecules.     

Identification of a T3-associated gamma delta T cell receptor on Thy-1+ dendritic epidermal Cell lines

The murine epidermis contains a subpopulation of bone marrow-derived lymphocytes that have a dendritic morphology and that express Thy-1 and T3 cell-surface antigens but not other markers (L3T4 or Lyt-2) characteristic of mature peripheral T lymphocytes. An alternative type of T cell receptor was earlier identified on a subpopulation of murine thymocytes with a similar phenotype (T3+, L3T4-, Lyt-2-), but not on peripheral murine T lymphocytes. Two independently derived Thy-1+, L3T4-, and Lyt-2- dendritic cell lines of epidermal origin that express a T3-associated disulfide-linked heterodimer composed of a 34-kilodalton gamma-chain and 46-kilodalton partner (the delta chain) have now been identified. Analysis of N-linked glycosylation revealed that this receptor is similar to that detected on thymocytes. These results demonstrate that Thy-1+ dendritic epidermal cell lines can express gamma delta T cell receptors in vitro and suggest that Thy-1+ dendritic epidermal cells express such receptors in vivo. The localization of these gamma delta T cell receptor-expressing cells in the epidermis may be of importance for understanding the function of these receptors.     

The T cell receptor

The primary structure of T cell receptor proteins and genes is well understood. Immunologists are now trying to understand the properties of these interesting molecules. Evidence suggests that T cell alpha beta receptors recognize a complex of an antigen-derived peptide bound to one of the cell-surface products of the major histocompatibility complex (MHC) genes. It is likely that alpha beta receptors and MHC proteins have coevolved to have some affinity for each other. During T cell development in the thymus, cells bearing self-reactive receptors are deleted by the mechanisms of tolerance, and cells are preferentially allowed to mature if they bear receptors that will be able to recognize antigen plus self-MHC after they have become full-fledged T cells. Some explanations for these phenomena have been tested, but no satisfactory theory can yet be proposed to account for them.     

Impaired B and T cell antigen receptor signaling in p110delta PI 3-kinase mutant mice

Class IA phosphoinositide 3-kinases (PI3Ks) are a family of p85/p110 heterodimeric lipid kinases that generate second messenger signals downstream of tyrosine kinases, thereby controlling cell metabolism, growth, proliferation, differentiation, motility, and survival. Mammals express three class IA catalytic subunits: p110alpha, p110beta, and p110delta. It is unclear to what extent these p110 isoforms have overlapping or distinct biological roles. Mice expressing a catalytically inactive form of p110delta (p110delta(D910A)) were generated by gene targeting. Antigen receptor signaling in B and T cells was impaired and immune responses in vivo were attenuated in p110delta mutant mice. They also developed inflammatory bowel disease. These results reveal a selective role for p110delta in immunity.     

Analysis of junctional diversity during B lymphocyte development

Immunoglobulin rearrangement is central to generating antibody diversity because of heterogeneity generated during recombination by deletion or addition of nucleotides at coding joints by the recombinase machinery. Examination of these junctional modifications revealed that the addition of nongermline-encoded nucleotides was more prevalent in adult versus fetal B cells, thus partially limiting the fetal antibody repertoire. In contrast, deletion of nucleotides occurs equivalently in B cells at different stages of development and at different points in B cell ontogeny. Finally, the bias in murine immunoglobulins for one DH segment reading frame occurs at the DHJH intermediate.     

Human T cell leukemia viruses use a receptor determined by human chromosome 17

Human T cell leukemia viruses (HTLV-I and HTLV-II) can infect many cell types in vitro. HTLV-I and HTLV-II use the same cell surface receptor, as shown by interference with syncytium formation and with infection by vesicular stomatitis virus (VSV) pseudotypes bearing the HTLV envelope glycoproteins. Human-mouse somatic cell hybrids were used to determine which human chromosome was required to confer susceptibility to VSV(HTLV) infection. The only human chromosome common to all susceptible cell hybrids was chromosome 17, and the receptor gene was localized to 17cen-qter. Antibodies to surface antigens known to be determined by genes on 17q did not block the HTLV receptor.