Characterization of lymphocytes from rejected and nonrejected islet xenografts.

A procedure is described for obtaining lymphocytes from xenografts of rat islets transplanted beneath the renal capsule of diabetic mice. In acute rejection of transplants of fresh rat islets, the lymphoid reaction was composed of 90% T lymphocytes with a predominance of Ly-2 cells. The Ly-2 cells were presumably cytotoxic T lymphocytes. On the other hand, if the islets are pretreated to avoid rejection, by culture in 95% O2 and administration of antilymphocyte serum to the recipients, the lymphocytes that are attracted by the graft are quite different. First, the percentage of T lymphocytes decreased, although they continue to be the most common cell. Second, however, the Ly phenotype was altered. Early after transplantation the Ly-2 population was decreased relative to Ly-1 cells. By day 70, the proportion of Ly-2 cells had returned to that of infiltrates actively rejecting the grafts, even though no rejection was evident. It is possible that the Ly-2+ cells present in nonrejected, established islet xenografts may be suppressor lymphocytes.