Induction of proliferative and cytotoxic responses in resting Lyt‐2+ T cells with lectin and recombinant interleukin 2

The lectin leucoagglutinin has been used to induce reactivity to interleukin 2 (IL2) in unseparated spleen cells and in highly purified Lyt-2+ lymph node T cells. Recombinant human IL2 and various other IL2-containing preparations, including concanavalin A-induced spleen cell supernatant, were compared for their capacity to support DNA synthesis and cytotoxic activity. In contrast to published reports, we found that the capacity of all preparations tested was identical in both functional assays, if they were adjusted to the same IL2 titer. Our inability to detect a requirement for an externally added cytotoxic T cell differentiation factor could either mean that IL2 is sufficient for the promotion of both proliferation and differentiation in leucoagglutinin-activated resting cytotoxic T cell precursors, or that under our experimental conditions, T cell differentiation factor is endogenously produced by Lyt-2+ T cells.