Irradiation of blood products can minimize the induction of graft-versus-host disease (GVHD) in recipients by eliminating the mitotic capacity from lymphocytes. We investigated the mitotic activity of lymphocytes with the aid of 3H-thymidine uptake after irradiation with various doses of X-ray in the range of 0 to 50Gy. This study showed that the mitotic activity of lymphocytes assessed by Mixed Lymphocyte Culture (MLC response) was completely inhibited by irradiation with 5Gy to each of blood products derived from 400ml of whole blood, including whole blood (WB), concentrated red cells (CRC) and platelet concentrates (PC). Irradiation of these blood products with 15Gy resulted in a 68-85% reduction in mitogen-stimulated 3H-thymidine uptake (mitogen response), and irradiation with 50Gy decreased the mitogen response by 96-99%. No differences were found in both morphology and viability between lymphocytes derived from 50Gy-irradiated and unirradiated CRC.
Since MLC response of lymphocytes seems to reflect closely the capability of lymphocytes to induce GVHD in patients, the risk of GVHD following transfusion of blood products would be eliminated by irradiation with X-ray of 15 Gy, which is three times minimal dose sufficient to abolish MLC response of lymphocytes.
