Induction of IL-2 receptor expression in vivo. Response to allogeneic cells.

Although the requirements for the induction of IL-2 receptor expression following lymphocyte stimulation in vitro have been well characterized, little information is available on the role of IL-2 and the IL-2 receptor in lymphocyte activation in vivo. We have established a quantitative assay for the measurement of IL-2-receptor-positive cells in the draining popliteal lymph node following the injection of allogeneic cells in the footpad. At the peak of the response more than 20% of the lymph node cells were IL-2-receptor-positive, and the majority of the IL-2-receptor-positive cells were Ly-2+ T cells and B cells. IL-2 receptor expression in vivo was closely associated with an increase in cell size and spontaneous and IL-2-driven proliferation, as well as with the induction of CTL activity specific for the donor strain. The model system described here should be useful in the further characterization of the mechanism of action in vivo of immunosuppressive drugs, antibodies, or lymphokines.