LYMPHOCYTE MEDIATED CYTOTOXICITY AND BLOCKING SERUM ACTIVITY AFTER BONE MARROW TRANSPLANTATION FOR SEVERE APLASTIC ANEMIA IN CHILDREN

Abstract

Studies were done to investigate whether peripheral blood lymphocytes, obtained from children who had received a successful bone marrow transplantation show an in vitro cytotoxic effect towards target cells of the recipient, to see if such cytotoxicity can be blocked by serum factors from the recipient and to test the possible correlation between the degree of lymphocyte cytotoxicity, the presence of blocking serum factors and the occurrence of graft versus host disease.Lymphocytes and serum, collected fron 7 patients with regular time intervals before and during 1 year after transplantation, were kept deep frozen and tested in one experiment. The test system used was the Takasugi-Klein microcytotoxicity assay using fibroblasts as target cells. Results show clearly that after successful bone marrow transplantation, lymphocyte cytotoxicity is present towards recipient antigens, which cannot be blocked by recipient serum. There appears to be no correlation between the degree of cytotoxicity and the occurrence and severity of graft versus host disease. In all patients cytotoxicity subsides after some time, ranging from 3 till 8 nonths after transplantation. Additional studies indicate that the occurrence of cytotoxicity towards recipient antigens cannot be explained by assuming the absence of suppressor cells. The difference between the in vivo and in vitro situation cannot yet be explained.