Immunologic Response of Patients With Acute Leukemia to Platelet Transfusions

Nine leukemic patients in aplasia received platelet concentrates from random donors over a period of 5 to 32 wk (an average of 31 transfusions per patient). All nine developed lymphocytotoxic activity (presumably HL-A antibodies) in their serum against cells from a panel of 40 selected donors within 20-50 days after transfusions were begun. Lymphocytotoxic activity markedly diminished in the sera of seven surviving patients over a period of 8-24 wk despite continued occasional platelet transfusions. When lymphocytotoxic activity was present in the serum of these patients, survival of transfused platelets was significantly reduced. Sera in which lymphocytotoxic activity was detected released endogenous serotonin (26 ± 5% SEM) from washed human platelets (but not from dog or rabbit platelets) when incubated at 37°C for 30 min. In contrast, sera from these patients, obtained when lymphocytotoxic activity was not detected, released minimal amounts of serotonin (6 ± 2%) and sera from nine healthy subjects released none (0 ± 1%). The ability of serum to release serotonin was abolished, and lymphocytotoxic activity was markedly diminished, after preincubation with allogeneic platelets.