Stimulation of mixed lymphocyte cultures and cytotoxic responses: evidence that T cells express SD but not LD antigens, whereas B cells express both.

By separating T and B cells from stimulator spleens it has been found that mixed lymphocyte response (MLR) and cytotoxic cells are generated in responder T cell populations by B but not by T stimulator cells in a wide variety of strain combinations. It is suggested that MLR-stimulating or LD antigens are expressed on B but not T cells, and that their presence is necessary in order to generate cototoxic responses to H-2K and/or H-2D (or SD) antigens which are present on both T and B cells. The finding that B cells and macrophages stimulate MLR is consistent with the hypothesis that Ia antigens, expressed on both these cell types but not on nylon column purified peripheral T cells, are the MLR-stimulating or LD determinants.