Alloimmune cytotoxic T cells: Evidence that they recognize serologically defined antigens and bear clonally restricted receptors.

Murine T cells immunized with allogeneic cells exert a cytotoxic effect on appropriate target cells, as measured by 51-Cr release. Lysis of the 51-Cr-labeled target can be inhibited by addition to the assay of unlabeled cells which bear target antigens. With variants of lymphoid tumors which express different amounts of serologically defined H-2 antigens as competitors in the assay, a positive correlation is shown to exist between the amount of serologically defined antigen and the degree of inhibition of T cell-mediated lysis. The immunized small lymphocytes are shown to be very poor inhibitors of 51-Cr release from target cells which are more susceptible to T cell-mediated lysis. This is interpreted as showing that small lymphocytes are bound very poorly by cytotoxic T cells. With H-2 cross-over strains which carry only the H-2K or H-2D antigens which a cytotoxic population is directed against, it is shown that, 1) approximately equal amounts of cytotoxicity are directed against the K and D antigens, and 2) separate cytotoxic T cells recognize the K and D antigens. Thus, by this criterion, cytotoxic T cells are monospecific and therefore do not acquire their antigen-specific receptors cytophilically.