Cellular requirements for generation of thymocyte stimulatory factor and characterization of its target cell.

The cellular requirements for the generation of thymocyte stimulatory factor, TSF, were defined, and the target cell for its activity was in part characterized. TSF production, which is triggered by concanavalin A stimulation of murine spleen cells, requires both an Lyt 1+23- cell and an Ia+ non-T accessory cell. The Ia+ cell does not bear surface Ig, is not killed by treatment with antithymocyte sera and C, and is partially depleted by Sephaadex G-10 filtration. TSF-augmentation of the thymocyte mitogenic response to Con A requires Lyt 1+, Ia- thymocytes, which are present in both the cortisone-sensitive and resistant populations. The relationship between TSF and other activities produced by Con A activation of spleen cells is discussed.