Comparison of the immunosuppressive effect of fractionated total lymphoid irradiation (TLI) vs conventional immunosuppression (CI) in renal cadaveric allotransplantation.

Beginning in November 1981, eight patients with end stage diabetic nephropathy underwent renal cadaveric transplantation after TLI. Transplantation was done between 2 to 11 days after the end of a fractionated TLI to a total dose of 20 to 30 Gy. During the same observation period, 60 nondiabetic patients with end stage renal disease of different origin also received a cadaveric kidney graft, with a conventional regimen of immunosuppression that consists of anti-lymphocyte-globulin, tapering high doses of prednisone, and azathioprine. In the TLI-treated group only a low maintenance dose of prednisone (15 mg) was given. Immunologic monitoring was performed after transplantation at regular intervals and was compared in both groups. Phytohemagglutinin (PHA)-, concanavalin A (con A)-, and pokeweed mitogen (PWM)-induced blastogenesis, as well as the mixed lymphocyte reaction (MLR) and the cell-mediated lympholysis (CML) decreased progressively during the first months after conventional immunosuppression to 50% of the pretransplantation level, and remained there for the first year after transplantation. These tests were much more impaired after TLI (less than 15% of pre TLI value) and again no recovery occurred during the first year. Natural killer (NK) cell activity progressively decreased from a mean value of 53% lysis before transplantation to 15% lysis at the end of the first year after transplantation in the conventionally treated patients. In TLI-treated patients, however, the NK activity, which declined during irradiation from 46% specific lysis to 12%, recovered rapidly after TLI to reach levels of 35 to 40% of specific lysis from the second month on after TLI. In both groups of patients the ratio of helper-inducer (TH) to suppressor-cytotoxic (TS) lymphocytes, as determined with monoclonal antibodies, progressively declined during the first 2 mo after transplantation to a low value of about 1.2. In TLI-treated patients however, this fall progressed further, so that very low levels (less than 0.6) were noticed from the third month on after TLI. The decline of the TH:TS ratio after TLI is due to an absolute increase in the number of suppressor cells. This is in contrast with the conventionally treated patients, where the low ratio is mainly provoked by a more important decrease of the helper cell population. These changes in the balance between TH and TS subpopulations are more frequently associated with positive functional suppressor cell assays in the TLI-treated patients.(ABSTRACT TRUNCATED AT 400 WORDS)