The immunosuppressive effect of extracorporeal irradiation of the blood using a portable 90Sr-90Y source and small transit doses.

The immunosuppressive effect of extracorporeal irradiation of the blood (ECIB) using small transit doses (TD) over a long time period was studied. The blood of 15 uremic patients undergoing hemodialysis in preparation for kidney transplantation was treated with15-, 25-, or 41-rad TDs for a total of 150 h, using the beta-emitting radioisotope 90Sr-90Y. The number of blood volumes (BV) irradiated ranged from 159 to 265. The irradiation resulted in selective lymphocytopenia, but the effect on the immune response of lymphocytes, as measured in vitro with lymphocyte transformation tests, varied. Six kidney transplantations were performed resulting in rejection in two cases, one which was easily reversed and one with many rejection episodes, ending in death. Thus treatment with small TDs over long periods can reduce lymphocyte counts, but any subsequent immunosuppressive effect is uncertain. Our results do not support the hypothesis that such irradiation can influence the immune response of lymphocytes without destroying the cells.