LOSS OF RT6 MESSAGE AND MOST CIRCULATING T-CELLS AFTER THYMECTOMY OF DIABETES-PRONE BB RATS

T cells expressing the RT6 surface alloantigen perform important immun oregulatory functions in the rat. Diabetes prone (DP) BB rats are defi cient in circulating RT6+ T cells and develop spontaneous autoimmune d iabetes mellitus. Transfusions leading to engraftment of RT6- T cells prevent the disease. Coisogenic diabetes resistant (DR) BB rats do cir culate RT6+ T cells and are free of disease. We investigated the basis for the deficiency of RT6+ T cells in the DP-BB rat and made the foll owing observations. 1. Thymectomy causes the rapid loss of most periph eral T cells in the DP-BB rat. 2. Concomitant with the loss of T cells is the total loss of mRNA encoding RT6. 3. In contrast to the effects observed in peripheral lymphoid tissues, thymectomy does not lead to a detectable loss in RT6+ protein found in the small intestine. We con clude that the deficiency of RT6+ peripheral T cells in the DP-BB rat is due either to their short life span or to their reduced proliferati ve capacity following release from the thymus.