EVIDENCE THAT CLONAL ANERGY IS INDUCED IN THYMIC MIGRANT CELLS AFTER ANTI-CD4-MEDIATED TRANSPLANTATION TOLERANCE

Diabetic (B6) (IE-) mice treated with a depleting regimen of anti-CD4 monoclonal antibody at the time of transplantation with A/J (IE(k)) islets of Langerhans showed indefinite acceptance of their islet allograft, as evidenced by persistent normoglycemia. To address the mechanisms involved in such anti-CD4 induced transplantation tolerance we studied potentially IE-reactive V(beta)11+ T cells from the tolerant allografted mice. Following complete repopulation of the CD4+ cells, both the CD4+V(beta)11+ and CD8+V(beta)11+ T cell subsets of the transplanted mice were unresponsive to anti-V(beta)11 specific crosslinking. In contrast, lymphocytes tested within the first ten days following transplant were responsive to anti-V(beta)11 specific crosslinking; this response decreased as a function of time and reached background levels by day 120 posttransplant. Sorting experiments indicated that the response of lymphocytes to anti-V(beta)11 specific crosslinking seen during the initial 120 days posttransplant was confined to the peripheral CD8+ cells; the repopulating CD4+V(beta)11+ T cells were unresponsive. In addition, administration of r-IL-2 at the time of transplantation induced rejection in anti-CD4-treated animals, again indicating that the peripheral CD8+ cells could respond shortly after transplant if provided with appropriate help. The decreasing response of CD8+ T cells from transplanted animals to anti-V(beta)11 stimulation was inversely correlated with the rate of migration of cells from the thymus to the periphery, implying that new thymic migrant V(beta)11+ cells, both CD4+ and CD8+, were rendered anergic upon encountering peripheral alloantigen. These data suggest the possibility that recent thymic migrants are rendered anergic upon encountering antigen in the periphery, a simple model to serve as a ''fail-safe'' mechanism to prevent autoreactivity.