FN18-CRM9 IMMUNOTOXIN PROMOTES TOLERANCE IN PRIMATE RENAL-ALLOGRAFTS

Background. Transplant tolerance, rather than immunity, may be favored in the setting of a lower mature lymphoid mass in the recipient induc ed by anti-T cell agents, A novel immunosuppressive agent, FN18-CRM9, known to specifically kill T cells with great potency, was evaluated i n a transplant model. Methods. In order to ablate recipient T cells, t he immunotoxin FN18-CRM9 was administered to rhesus monkey recipients of MHC-mismatched renal allografts, Donor lymphocytes were injected in trathymically into some animals. Results. All monkeys with T-cell depl etion by immunotoxin had prolonged allograft survival, and tolerance c onfirmed by skin grafting has been confirmed in five of six long-survi ving recipients. Conclusions. In this clinically relevant model, profo und but transient T-cell depletion by a single agent substantially pro motes tolerance.