Immunological memory is regulated in the enhanced rat renal allograft recipient

SUCCESSFUL transplantation of renal allografts without compromising the immune system of the recipient is a goal of clinical transplantation. The enhancement of kidney allografts in the inbred rat provides an experimental system satisfying this goal. Pretreatment of recipient animals with antigen and antibody, alone or in combination, has produced the indefinite survival of renal allografts 1–4 , but the mechanisms underlying this specific elimination of responsiveness to the donor graft have not been completely elucidated. Three alternative mechanisms have been proposed to explain the maintenance of the enhanced state: (1) deletion or alteration of donor antigens on the graft; (2) deletion of the relevant antigen-reactive cells; (3) regulation of the host response to the graft. We discuss these suggestions here, and report our own work on enhancement, giving evidence for the role of immunological memory regulation.