Recognition of self antigens by skin-derived T cells with invariant gamma delta antigen receptors

Thy-1+ dendritic epidermal T cells (dECs) express invariant gamma delta antigen receptors and are found in intimate contact with keratinocytes in murine epidermis--thus raising the possibility that keratinocytes express a ligand for the antigen receptor of these T cells. Thy-1+ dECs were stimulated to produce lymphokines by interaction with keratinocytes in vitro. This stimulation was mediated through the dEC antigen receptor and did not appear to be restricted by the major histocompatibility complex. Thus, dECs can recognize self antigens and may participate in immune surveillance for cellular damage rather than for foreign antigens.     

Characterization of T cell receptor gamma chain expression in a subset of murine thymocytes

While much information exists about the structure and function of the clonally distributed T cell receptor (TCR) alpha beta heterodimer, little is known about the gamma protein, the product of a third rearranging TCR gene. An antiserum to a carboxyl-terminal peptide common to several of the murine gamma chain constant regions and a monoclonal antibody to the murine T3 complex were used to identify products of this TCR gene family in a subpopulation of Lyt2-, L3T4- thymocytes. This subpopulation does not express TCR alpha or full-length TCR beta messenger RNA. The gamma chain is a 35-kilodalton (kD) protein that is disulfide-bonded to a 45-kD partner and is associated with the T3 complex. Analysis of the glycosylation pattern of this thymic gamma chain revealed that the major variable region gamma (V gamma) gene transcribed in activated peripheral T cells is absent from this subpopulation. The cells that bear this second T cell receptor may therefore represent a distinct lineage differentiating within the thymus.     

In vivo modulation of cytolytic activity and Thy-1 expression in TCR-gamma delta+ intraepithelial lymphocytes

Although the functional aspects of the alpha beta T cell antigen receptor (TCR) found on most peripheral T cells are well described, the function of the gamma delta TCR remains unclear. Murine intraepithelial lymphocytes (IEL) of the small intestine are CD8+, express the gamma delta TCR, and are constitutively lytic. Fresh IEL from germ-free mice had no lytic activity. Moreover, whereas IEL from normal mice are 30 to 50 percent Thy-1+, IEL from germ-free did not express Thy-1. Acclimation of germ-free mice to nonsterile conditions resulted in the generation of Thy-1+ IEL and induction of lytic activity. Thus CD8+ TCR-gamma delta IEL were regulated by externally derived stimuli via a specific functional interaction between IEL and gut-associated antigens.     

Requirement for positive selection of gamma delta receptor-bearing T cells.

The alpha beta and gamma delta T cell receptors for antigen (TCR) delineate distinct T cell populations. TCR alpha beta-bearing thymocytes must be positively selected by binding of the TCR to major histocompatibility complex (MHC) molecules on thymic epithelium. To examine the requirement for positive selection of TCR gamma delta T cells, mice bearing a class I MHC-specific gamma delta transgene (Tg) were crossed to mice with disrupted beta 2 microglobulin (beta 2M) genes. The Tg+beta 2M- (class I MHC-) offspring had Tg+ thymocytes that did not proliferate to antigen or Tg-specific monoclonal antibody and few peripheral Tg+ cells. This is evidence for positive selection within the gamma delta T cell subset.     

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.     

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.     

Epidermal viral immunity induced by CD8alpha+ dendritic cells but not by Langerhans cells

The classical paradigm for dendritic cell function derives from the study of Langerhans cells, which predominate within skin epidermis. After an encounter with foreign agents, Langerhans cells are thought to migrate to draining lymph nodes, where they initiate T cell priming. Contrary to this, we show here that infection of murine epidermis by herpes simplex virus did not result in the priming of virus-specific cytotoxic T lymphocytes by Langerhans cells. Rather, the priming response required a distinct CD8alpha+ dendritic cell subset. Thus, the traditional view of Langerhans cells in epidermal immunity needs to be revisited to accommodate a requirement for other dendritic cells in this response.     

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.     

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.     

Novel interleukin-2 receptor subunit detected by cross-linking under high-affinity conditions

Interleukin-2 (IL-2) binds to both high- and low-affinity classes of IL-2 receptors on activated T lymphocytes. Only the high-affinity receptors are involved in receptor-mediated endocytosis and normally transduce the mitogenic signals of IL-2; however, the structural features distinguishing the high- and low-affinity receptors are unknown. When 125I-labeled IL-2 was chemically cross-linked to activated human T lymphocytes, two major bands were identified. First, as predicted, a 68- to 72-kilodalton band, consisting of IL-2 (15.5 kilodaltons) cross-linked to the IL-2 receptor (55 kilodaltons), was observed. Second, an unpredicted 85- to 92-kilodalton moiety was detected. This band was not present when IL-2 was cross-linked to transfected C127 cells, which exclusively express low-affinity receptors. The data presented are most consistent with the existence of a 70- to 77-kilodalton glycoprotein subunit (p70) which, upon associating with the 55-kilodalton low-affinity receptor (p55), transforms it into a high-affinity site. It is proposed that p55 and p70 be referred to as the alpha and beta subunits, respectively, of the high-affinity IL-2 receptor.     

A glycophospholipid tail at the carboxyl terminus of the Thy-1 glycoprotein of neurons and thymocytes

Cell surface molecules of eukaryotic cells have been considered to be integrated into the membrane bilayer by a transmembrane protein sequence. The Thy-1 antigen of rodent thymocytes and brain was the first eukaryotic membrane molecule for which biochemical data clearly suggested membrane integration via a nonprotein tail. Direct evidence is now presented showing that a glycophospholipid structure is attached to the carboxyl-terminal cysteine residue and that 31 carboxyl-terminal amino acids predicted from the Thy-1 complementary DNA sequence are not present in the mature glycoprotein. These experimental results raise questions concerning signaling across a cell membrane since antibodies to Thy-1 can stimulate T lymphocytes to release lymphokines and undergo cell division.     

Recognition of HLA-A2 by cytotoxic T lymphocytes after DNA transfer into human and murine cells

A gene coding for the major histocompatibility antigen HLA-A2 was transferred into human HLA-A2 negative M1 cells and murine L cells. Following transfection, these cells expressed molecules at the cell surface that are biochemically indistinguishable from HLA-A2 antigens on the human cell line JY from which the HLA-A2 gene was isolated. The M1A2 cells were recognized and lysed by a cytolytic T-cell clone specific for HLA-A2. The transfected L cells which express HLA-A2 in association with human beta 2-microglobulin were not lysed by this T-cell clone. The specific cytolysis of M1A2 cells could be inhibited by monoclonal antibodies to HLA-A2, and monoclonal antibodies to T3, T8, and LFA-1 on cytotoxic T lymphocytes. These results suggest that killing by allospecific T cells requires HLA-A2 antigens as well as other species-specific structures on the target cell surface.     

T cell CD3-zeta eta heterodimer expression and coupling to phosphoinositide hydrolysis

The T cell antigen receptor consists of an antigen-binding heterodimer that is noncovalently associated with at least five CD3 subunits (gamma, delta, epsilon, zeta, and eta). The CD3-zeta chains are either disulfide-linked homodimers (CD3-zeta 2) or disulfide-linked heterodimers with eta (CD3-zeta eta). Variants of a murine antigen-specific T cell hybridoma that express normal amounts of CD3-zeta 2 but decreased amounts of CD3-zeta eta were isolated. When activated, the parental cell line increased both phosphatidylinositol hydrolysis and serine-specific protein kinase activity to a much greater extent than the variants. In contrast, the activation of a tyrosine-specific kinase after stimulation with a cross-linking antibody to CD3 was similar among these cells. There was a positive linear relation between the expression of CD3-zeta eta and phosphoinositide hydrolysis stimulated by the TCR, suggesting a differential coupling of the T cell alpha beta heterodimer to signal transduction mechanisms due to alpha beta association with either CD3-zeta 2 or CD3-zeta eta.     

Recognition by human V gamma 9/V delta 2 T cells of a GroEL homolog on Daudi Burkitt's lymphoma cells

All human gamma delta T cells coexpressing the products of the variable (V) region T cell receptor (TCR) gene segments V gamma 9 and V delta 2 recognize antigens from mycobacterial extracts and Daudi cells. Exogenous and endogenous ligands on the cell surface, homologous to the groEL heat shock family, induced reactivities that resembled superantigen responses in this major subset of human peripheral blood gamma delta T cells. Stimulation of human V gamma 9/V delta 2 T cells is not restricted by human leukocyte antigens (HLA), including nonpolymorphic beta 2-microglobulin (beta 2M)-associated class Ib molecules. These data may be important for understanding the role of gamma delta T cells in autoimmunity and in responses to microorganisms and tumors.     

Thymic origin of intestinal alphabeta T cells revealed by fate mapping of RORgammat+ cells

Intestinal intraepithelial T lymphocytes (IELs) are likely to play a key role in host mucosal immunity and, unlike other T cells, have been proposed to differentiate from local precursors rather than from thymocytes. We show here that IELs expressing the alphabeta T cell receptor are derived from precursors that express RORgammat, an orphan nuclear hormone receptor detected only in immature CD4+CD8+ thymocytes, fetal lymphoid tissue-inducer (LTi) cells, and LTi-like cells in cryptopatches within the adult intestinal lamina propria. Using cell fate mapping, we found that all intestinal alphabeta T cells are progeny of CD4+CD8+ thymocytes, indicating that the adult intestine is not a significant site for alphabeta T cell development. Our results suggest that intestinal RORgammat+ cells are local organizers of mucosal lymphoid tissue.     

Molecular cloning of the zeta chain of the T cell antigen receptor

The T cell antigen receptor is a multi-subunit receptor complex present on the surface of all mature and many developing T cells. It consists of clonotypic heterodimers noncovalently linked to five invariant chains that are encoded by four genes and referred to as the CD3 complex. The CD3 gamma, delta, and epsilon chains have been molecularly characterized. In this report the molecular cloning of a complementary DNA encoding the zeta chain of the murine T cell antigen receptor is described. The predicted protein sequence of the zeta chain suggests a structure distinct from those of any of the previously described receptor subunits.