Studies of thymus-derived and bone marrow-derived lymphocytes in renal transplant patients.

Serial studies of levels and responsiveness of T and B lymphocytes were performed in human renal allograft recipients. Patients given prednisolone-azathioprine immunosuppression had only mild falls in levels and responsiveness of T cells. Patients given a quality controlled ATG preparation had marked and relatively selective falls in levels of T cells associated with a marked fall in T cell responsiveness as measured by PHA and Con-A responsiveness. In vivo correlates of this severe T cell deficiency suggest that T lymphocytes are central to acute allograft rejection and that acute severe T cell deficiency is not associated with risk of infectious complications above and beyond those seen in patients suppressed with prednisone-azathioprine alone. These studies suggest that ATG, produced under quality control conditions and having rather selective anti-T cell activity, is a useful adjunctive immunosuppressive agent for human renal transplantation.