Showing papers by "Susumu Tonegawa published in 1991"

Extrathymic origin of intestinal intraepithelial lymphocytes bearing T-cell antigen receptor gamma delta.

Abstract: The kinetics of postnatal intestinal colonization by T cells carrying gamma delta and alpha beta T-cell antigen receptors were studied in nude and normal mice by flow cytometry and immunohistology. Furthermore, gamma delta and alpha beta T-cell development was analyzed in lethally irradiated mice that were reconstituted by fetal liver precursors with or without a thymus. Our results establish that a major subpopulation of gamma delta intestinal intraepithelial lymphocytes is produced from uncommitted precursors at extrathymic sites. This work further shows that a small pool of T cells carrying alpha beta T-cell receptors can also differentiate extrathymically from CD3- fetal liver precursors but with rates of production and peripheral expansion much reduced as compared with those observed in thymus-bearing animals.

Creation of a large genomic deletion at the T-cell antigen receptor beta-subunit locus in mouse embryonic stem cells by gene targeting.

Abstract: Recently it has become possible to introduce predesigned mutations into a given gene in the mouse germ line by homologous recombination in embryonic stem cells. The mutations are usually introduced by inserting the neomycin phosphotransferase gene into an exon of a particular gene. Here we describe an extension of this method that can result in at least a 15-kilobase-long deletion. The deletion created in the present work encompasses one of the two diversity gene segments of the mouse T-cell receptor beta-subunit locus, 10 out of the 12 joining gene segments, and both constant gene segments. This strategy is a valuable alternative to sequential targeting of multiple genes forming a gene cluster, could simplify the construction of plasmids to be used for targeting, and could be the solution for inactivating small genes that have eluded conventional targeting approaches.

Highly restricted expression of the thymus leukemia antigens on intestinal epithelial cells.

Abstract: The TL region of the major histocompatibility complex of the mouse contains dozens of tandemly arranged class I genes, including those encoding the thymus leukemia (TL) antigens. TL antigens have been thought to be expressed only on the surface of some T lineage cells, namely immature thymocytes of some mouse strains (TL+ strains), some leukemia cells, and activated T cells. While the function of TL antigens is unknown, recent studies have implicated the products of at least some TL region class I genes as molecules that present antigens to gamma/delta T cells. Since some gamma/delta T cells are known to be specifically associated with certain epithelial tissues, we have investigated the expression of some TL region class I genes in a variety of epithelium-containing tissues. Our results show that the TL antigen gene of C57BL/6 mice, T3b, and the TL antigen genes of BALB/c mice, T3d (previously T3c) and T18d (previously T13c), are highly expressed in the epithelium of the small intestine. In the case of T3b, we further show, using a T3 product-specific antibody, that its product is expressed on the surface of the columnar epithelial cells. In addition, we demonstrated that two other TL region class I genes of C57BL/6 origin, T9b and T21b, are also expressed nearly exclusively in intestinal epithelial cells. These results are consistent with the hypothesis that the products of these TL region class I genes are recognized by gamma/delta T cell receptors of intestinal intraepithelial lymphocytes, a subset of gamma/delta T cells that is localized in the intestinal epithelium and has a restricted V gamma repertoire. Finally, our study indicates that the relative levels of expression of the two homologous TL antigen genes, T3d and T18d, differ widely between the thymus and the intestine.

Surface expression of alternative forms of the TCR/CD3 complex.

Abstract: T-cell antigen receptor (TCR) heterodimers of both the alpha beta and gamma delta types are expressed at the surface of T cells only in association with a complex of invariant chains called CD3. The requirement for individual CD3 components to achieve TCR surface expression was examined by cotransfection of a non-T-cell line with TCR alpha and beta, as well as CD3 delta, epsilon, gamma, and zeta, cDNAs. Both transient and stable transfectants expressing TCR and CD3 epitopes at the cell surface were generated. By transfection of TCR and CD3 components in different combinations, the TCR chains, as well as the CD3 epsilon and zeta chains, were each shown to be essential for reconstituting surface expression. On the other hand, CD3 delta and gamma chains could be used alternatively, providing evidence for two different types of TCR/CD3 complexes.

Recognition of MHC TL gene products by gamma delta T cells.

Abstract: We have studied the ligand specificity of a gamma delta T-cell receptor (TCR) derived from a mouse T-cell hybridoma (KN6). KN6 cells reacted with syngeneic (C57BL/6) cells from various origins (splenocytes, thymocytes, peritoneal exudate cells, etc.) and cells from many different mouse strains. KN6 reactivity against cells from a panel of congenic and recombinant mouse strains demonstrated that the ligand recognized by KN6 is controlled by an MHC-linked gene that most probably maps in the TL region. We cloned this gene and formally proved that it does map in the TL region. This gene turned out to be a novel class I gene (designated T22b) belonging to a hitherto unidentified cluster of TL region genes in strain C57BL/6. This gene was expressed in many different tissues and cell types. We also examined the tissue expression of several other TL genes. One of these, the structural gene (T3b) encoding the thymus leukemia (TL) antigen from C57BL/6 mice, was specifically expressed in the epithelium of the small intestine. Since the intestinal epithelium of the mouse is known to be the homing site for a subset of gamma delta T cells (i-IEL) bearing diverse TCR with V7 rearranged gamma chains, we propose that the T3b gene product is part of the ligand recognized by some of the i-IEL. Our data support the idea that gamma delta T cells might be specific for non-classical class I or class I-like molecules and suggest that gamma delta TCR and non-classical MHC co-evolved for the recognition of a conserved set of endogenous or foreign peptides.

Identification of a T-cell-specific enhancer at the locus encoding T-cell antigen receptor gamma chain.

Abstract: The gamma delta and alpha beta T-cell antigen receptor (TCR) heterodimers are expressed in a lineage-specific, mutually exclusive manner Regulation of expression occurs at the transcriptional level A 13-kilobase (kb) stretch of DNA encompassing variable-joining-constant segments V gamma 4-J gamma 1-C gamma 1 of the murine gamma-chain gene was examined for the presence of transcriptional enhancing elements by a transient transfection assay DNA fragments from this region were inserted into a test plasmid containing a heterologous promoter fused to the human growth hormone gene An 1800-base-pair (bp) fragment located 3 kb 3' to C gamma exon III was found to display enhancing activity in several T-cell lines Maximum enhancing activity could be localized further to fragments as small as 400 bp in some cell lines Nucleotide sequence analysis of this 400-bp segment revealed homologies to previously described core enhancer elements and to other TCR gene enhancers The TCR gamma-chain gene enhancer is active in both gamma delta and alpha beta T cells, indicating that it is not primarily responsible for lineage-specificity of expression, but it is inactive in non-T-cells

Heterodimeric T lymphocyte receptor subunit

Abstract: Disclosed is a heterodimeric T lymphocyte receptor subunit. The subunit consists of variable, joining, constant, transmembrane, and cytoplasmic regions. The structure, amino acid, and nucleotide sequence of the lymphocyte receptor subunit were determined using cDNA clones derived from a functional murine cytotoxic T lymphocyte clone. The genes corresponding to these cDNA are expressed and rearranged specifically in T cells and have significant sequence homologies to immunoglobulin V and C genes. T cell receptor subunits may be produced from the cDNA clones. The protein molecules may be further used for the production of T-cell clone specific antibodies.