Interleukin-1 stimulates diacylglycerol production in T lymphocytes by a novel mechanism

We have investigated the biochemical mechanism by which interleukin-1 (IL-1) serves as a comitogen with agents that directly activate the antigen receptor in T lymphocytes. We have studied the human T cell line Jurkat, which can be stimulated to produce Interleukin-2 by treatment with antibodies that bind to the CD3-antigen receptor complex and hence represents a model system for T cell activation. Using highly purified, recombinant human IL-1, we show that IL-1 stimulates rapid diacylglycerol and phosphorylcholine production from phosphatidylcholine (PC) in the absence of phosphatidylinositol turnover in Jurkat cells. This effect is also observed in peripheral blood T cells and a murine T cell line. The EC50 for IL-1 was 28 fM, and PC hydrolysis was detectable within 5 sec at 37 degrees C. The murine cell line had typical high-affinity IL-1 receptors (kd = 7 X 10(-11) M). However, we were unable to detect IL-1 binding to Jurkat cells. This reaction occurs via a novel mechanism and may explain the comitogenic activity of IL-1 in T lymphocyte activation as well as many of the pleiotropic biologic effects of this cytokine.