Twelve leukocyte antigens have been determined by the method of cytotoxicity in v~tro on leukoblasts from 38 patients with acute leukemia, using two batteries of isoimmune human sera. None of these antigens was absent in this leukemic population. The presence of the leukocyte antigens 1, 3, 4, 6, and 7 of the Hu-1 system (5) was confirmed by absorption experiments. In 17 patients, the leukocyte group defined on leukoblasts during the acute phase of the disease was found to be identical to that

more »

... etermined on lymphocytes from the same patients during the remission period. No qualitative antigenic alterations of these alloantigens were found on the leukoblasts from patients with acute leukemia.