Identification of a major Leu 7/OKT 8 positive T-lymphocyte subpopulation in renal transplant patients pre-treated with total lymphoid irradiation.

When pretreated with total lymphoid irradiation, renal allograft recipients have an increased percentage of OKT 8 positive (cytotoxic/suppressor) T cells among their peripheral blood T lymphocytes (PBL) (56 +/- 21%) and also of Leu 7 PBL (47 +/- 18%). In contrast, transplant patients treated with azathioprine or cyclosporine A have percentages of OKT 8 and Leu 7 positive PBL, similar to control persons (respectively 29 +/- 13, 33 +/- 10, 30 +/- 10 for the OKT 8+ cells and 8 +/- 7, 11 +/- 6 and 15 +/- 9 for the Leu 7+ cells). After purification, about two thirds (70%) of the OKT 8 positive, OKT 3 positive, T lymphocytes of TLI patients were shown to co-express the Leu 7 antigen. It is concluded that after TLI, an increase of OKT 3+, OKT 8+ and Leu 7+ lymphocytes takes place, a subset previously described to be present in low numbers in control persons and whose function is still unclear. This expansion after TLI should allow functional identification of this subset and might contribute to the understanding of the immunosuppressive effects of TLI.