Con A-stimulated thymocytes produce interleukin 2 after removal of Lyt-1 positive cells

Mouse lymphocytes produce several lymphokines, including interleukin 2 (IL-2) and colony-stimulating factors (CSFs) following stimulation with T-cell mitogens. However, very little IL-2 is produced by thymocytes upon concanavalin A (Con A) stimulation. Strong selective inhibition of IL-2 production was observed when fresh spleen cells were mixed with Con A-activated thymocytes. Sorting of populations on the basis of antigenic phenotype showed that the cell mediating the blockage in IL-2 secretion is a large T cell expressing markers for both Lyt-1 and Lyt-2. This specific inhibition of IL-2 accumulation was not mediated by a soluble product, or by absorption on expressed IL-2 receptors on the activated thymocytes. Removal of the Lyt-1 positive cells from a thymocyte population renders it capable to produce IL-2 upon Con A stimulation, indicating a functional role of these cells.