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This study has evaluated whether preferential pairing occurs between TCR alpha- and beta-chains expressing specific V alpha and V beta gene products in the mature peripheral T cell population, as a result of either thymic selection or of structural constraints on chain pairing. The association of specific V alpha products with specific V beta products on individual T cells was found, in multiple instances, to be highly selective. Moreover, patterns of preferential V alpha-V beta association were highly strain-specific and were independently expressed in CD4+ and CD8+ T cell subsets. Although these findings do not exclude the possibility that structural constraints may limit V alpha-V beta pairing in other instances, they indicate that the observed instances of skewed expression are not caused by structural constraints in chain pairing. Rather, they suggest that strain-specific selective events alter the expressed V alpha V beta repertoire as a result of recognition of self or environmental Ag during T cell repertoire selection.

CD8 is a heterodimeric membrane glycoprotein on MHC class I-restricted T lymphocytes that cooperates with the alpha beta CD3 TCR in the recognition of MHC class I molecules presenting antigenic peptides. Co-operation has two components: enhancement of the affinity of MHC/peptide-TCR interaction, and signal transduction through the T cell membrane. The cytolytic function of CTL is primarily dependent on the affinity-enhancement component of CD8-TCR cooperation whereas activation of resting CD8+ T cells is primarily dependent on transmembrane signaling. Using a panel of mAb, two to the alpha-chain and three to the beta-chain of CD8, we investigated the relationships between epitopes and functional regions of the CD8 molecule. Two of the antibodies, one to the alpha-chain and one to the beta-chain of CD8, inhibit the cytolytic function of CTL but not the generation of CTL from resting T cells. Another two antibodies, also one to the alpha- and one to the beta-chain, inhibited the generation of CTL while enhancing the cytolytic function of CTL. These results suggest that both the alpha- and beta-chain of CD8 possess two distinct regions, one involved in affinity enhancement and the other in transmembrane signaling. The former may be the MHC class I-binding region whereas the latter may associate with the alpha beta CD3 TCR. The data can explain the apparent functional equivalence of CD8 alpha alpha homodimers and alpha beta heterodimers.

An AMLR in which precultured cells proliferated in response to fresh non-T cells is described. In our system, the responder is human peripheral blood mononuclear cells precultured in the autologous fresh plasma for up to 16 days, and the stimulator is fresh autologous non-T cells. Results suggested that there were two subpopulations of autoreactive cells obtained from the preculture; the high and low density small lymphocytes, both having ERF activity. The autoreactivity of low density cells was augmented when either macrophages or N-ERF-cells were depleted from PBM and thereafter precultures wre performed. A survey of the functional characteristics of the responding cells showed that the responding cells had NK activity against Molt-4 cells but had no significant ADCC activity against target CRBC. Mechanisms for the induction of autoreactive cells by the preculture in the presence of autologous fresh plasma are discussed.

Two types of H-Y antigen-specific cloned T cell lines were established. Clone 2-1 is an IAb restricted proliferating T cell line and clone 10-2 is an H-2Db restricted proliferating and cytotoxic T cell line. Clone 2-1 proliferated in response to H-Y antigen with an IAb restriction in the absence of IL 2. IAb mutant B6.C-H-2bm12 (bm12) mice did not stimulate this clone. This defect may be the cause of the unresponsiveness to H-Y antigen with cytotoxic T lymphocytes (CTL) in bm 12 mice (i.e., the failure of activation of H-Y-specific helper T cells). Although (B10.A X bm12)F1 mice are known to show functional complementation, as demonstrated by the presentation of insulin to helper T cells and the H-Y-specific CTL response, the F1 male cells could not stimulate this clone. The IA determinant restricting H-Y antigen presentation to helper T cells and/or the H-Y antigenic determinant seems to differ between C57BL/6 (B6) and the F1 mice. Monoclonal anti-IAb antibodies but not anti-H-Y antibodies blocked the proliferation of this clone. The clone had no cytotoxic activity unless Con A was added to the cytotoxicity assay culture. Clone 10-2 proliferated in response to H-Y antigen with an H-2Db restriction. Proliferation was not observed unless specific stimulator cells and IL 2 were supplied to the culture; IL 2 alone could not support this clone. The clone did not respond to male cells from the H-2Db mutant B6.C-H-2bm14 (bm14). The clone had cytotoxic activity against male H-2Db+ cells but not against male bm14 cells. This evidence indicates that the mutation of bm14 occurred in the structural gene coding for a molecule on which a determinant restricting the recognition of H-Y antigen by B6 CTL exists. The phenotypes of clone 2-1 were Thy-1.2+, Ly-1.2-, Ly-2.2-, IAb-, and H-2Kb+, and the phenotypes of clone 10-2 were Thy-1.2+, Ly-1.2-, Ly-2.2+, IAb-, and H-2Kb+.

In the course of the culture of an autologous mixed lymphocyte reaction (AMLR), T cells proliferated in response to autologous non-T cells, and differentiated to cytotoxic T cells (AMLR killers). DNA synthesis was necessary to generate AMLR killers, as the elimination of autoreactive proliferating cells with BUdR and UV light completely abrogated AMLR killer cytolysis. Amlr killers lysed various lymphoid cell lines, including autologous B cell lines, autologous or allogeneic mitogen blasts stimulated by Con A, PHA, or pokeweed mitogen, variious nonlymphoid cell lines derived from human, mouse, or rat, and weakly normal autologous or allogeneic non-T cells. KMT-17, methylcholanthrene-induced rat fibrosarcoma, was the only resistant cell line to have been tested. AMLR killers had characteristics similar to NK cells, Major histocompatibility antigens were not the target antigens for AMLR killers. AMLR killers distinguished the blasts stimulated by alloantigens as self from the blasts stimulated by mitogens as non-self.

Human T cells were separated with neuraminidase-treated autologous erythrocytes into auto-rosette-forming cells (ARFC) and non-ARFC (N-ARFC). These 2 subsets were examined for reactivity to autologous non-T cells. When N-ARFC were stimulated by autologous non-T cells, blastogenesis was weak; ARFC, however, proliferated vigorously. ARFC were revealed to be the major subset that responded and proliferated in autologous mixed lymphocyte reaction (AMLR). AMLR-primed cells were restimulated by autologous or allogeneic non-T cells to study self recognition in relation to HLA complex. Self recognition by AMLR-primed cells was closely related to HLA complex, and absolute identity of HLA complex was necessary to recognize allogeneic cells as self. In addition, in respect to the responder cell difference between AMLR and allogeneic MLR, the reactivity of 2 kinds of cells (i.e., AMLR-primed cells and alloreactive cells) strongly suggested that autoreactive T cells were distinguished from alloreactive T cells.