Expression of the T Cell Gamma Gene by a Functionally Defined Human T Cell Clone Characterization at DNA, RNA, and Cell Membrane Level

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Abstract
In the present study we describe one CD2+CD3+ clone termed DS6 which expressed neither CD4 nor CD8 differentiation antigens and failed to react with WT31, a monoclonal antibody directed against the T cell antigen receptor .alpha./.beta. heterodimer. This clone was isolated from peripheral blood T lymphocytes of a patient with a prolonged immunodeficiency after allogeneic bone marrow transplantation. Normal-sized T cell .gamma. gene transcripts were detected in DS6 by northern analysis, whereas no mature .beta. or .alpha. chain mRNA were found. The rearrangement of TCR.beta. chain genes and T cell .gamma. genes was analyzed. While in DS6, TCR.beta. chain genes remain in germinal configuration, and a unique pattern of monoallelic T cell .gamma. gene rearrangement was observed. The rearrangement involves the recently described V.gamma.5 segment and the J.gamma.1 joining segment, which is located upstream of the C.gamma.1 constant region. To determine the molecular structure present on DS6, an immunoprecipitation was performed with monoclonal anti-CD3 antibody and a rabbit antiserum raised against .gamma. protein. We have observed, in association with the CD3 complex, a 90 kDa structure which under reducing conditions resolves into three subunits of 45, 40 and 37 kDa. We demonstrated that the rabbit anti-.gamma. serum only immunoprecipitates the two lower bands. The upper band corresponds to a presently undefined T cell receptor chain. Next, we showed the non major histocompatibility complex (MHC)-restricted cytolytic activity exhibited by these CD3+CD4-CD8-cloned T cells and inhibition of the natural killer (NK)-like activity by the anti-CD3 monoclonal antibody. The triggering of CD2 or CD3 molecules increased IL-2 receptor expression on DS6 but failed to induce cell proliferation. This contrasts with recent results obtained with .gamma.-expressing T cell clones and illustrates the functional heterogeneity of the cells bearing the second T cell receptor.

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