Decreased neutrophil bactericidal activity in acute leukemia of childhood.

Neutrophil (PMN) bactericidal activity, phagocytosis, and nitroblue tetrazolium (NBT) reduction were evaluated in 18 children with untreated or relapsing acute leukemia and 20 children in hematologic remission. Half of the patients in relapse demonstrated abnormal PMN bactericidal activity, while remission patients had essentially normal PMN bactericidal activity. Phagocytosis of Staphylococcus aureus was normal in relapse and remission subjects. NBT reduction by PMN's of leukemic patients was significantly lower than that of controls, but there was no correlation between decreased NBT-reductase activity and decreased bactericidal power. Six patients in remission had received intensive chemotherapy for more than 4 years, and all demonstrated normal PMN functions. Among relapse patients with abnormal PMN bactericidal activity 63% eventually developed severe bacterial infections. By comparison, 20% of the relapse patients with normal PMN bactericidal activity subsequently developed severe infections. The PMN dysfunction observed in relapse patients suggests that abnormal PMN bactericidal activity may contribute the increased susceptibility to bacterial infections during leukemic relapse.