Early experience with anti-Tac in clinical renal transplantation.

T H E SEARCH for more effective and Jess broadly toxic immunosuppressive agents remains a major goal of transplantation research. One approach to achieving more specific immunosuppression is to target only those lymphocytes responding to an allograft by directing therapy at activation antigens. Of these antigens, the interleukin-2 receptor (IL-2R) has proven of particular interest, both because of its important biological role in the activation T-cells and because of extensive animal model experience with anti-IL-2R monoclonal antibody (Mab) therapy.-6 Anti-Tac is a murine Mab with specificity for the 55KD beta subunit of the human IL-2R. 7 Anti-Tac blocks binding of IL-2 to its receptor and prevents association of the alpha and beta chains of the receptor to form the high affinity IL-2R. Recent work from our laboratory has shown that anti-Tac as a single agent will significantly delay rejection of renal allografts in cynomolgus monkeys. Encouraged by these results, we have initiated a randomized trial of prophylactic therapy with anti-Tac in clinical renal transplantation. This study presents our early experience with three protocols for the use of this agent.