T cell differentiation and generation of the antigen‐specific T cell repertoire in man: observations in MHC class II deficiency

SUMMARY The circulating T cell pool of an MHC class II‐deficient patient was shown to lack the MHC class II‐specific T cell functions. This was demonstrated by the absence of MHC class Il‐specific alloreactive T cells and a substantially decreased number of circulating CD4 + lymphocytes. The patient's T cells did respond to an allostimulus, although the restriction pattern of this reaction remains speculative. The function and distribution of peripheral T cell subsets from the patient resemble findings in MHC class II‐deficient mice, which also lack interaction of T cell precursors with MHC class Il‐bearing accessory cells during thymic differentiation. Our data support the concept that Tcell differentiation in humans is similar, and that the human MHC‐restricted Tcell repertoire depends on prior interaction of T cell precursors with self MHC.