Immunotherapy with interleukin-2 (IL-2) and lymphokine-activated killer (LAK) cells generated from autologous lymphocytes has produced significant tumor regressions in patients with advanced cancer. In the current study, we reviewed the hematologic effects associated with this therapy in our initial 42 patients. Eighty-eight percent of the treated patients developed anemia that required greater than or equal to 4 units of red cell transfusions, and 43% received at least 8 units. Only a blood loss of 2 to 3 units could be attributed to repeated phlebotomy, cytophereses, and hemodilution. IL-2 administration also resulted in thrombocytopenia as well as lymphopenia and eosinophilia. Forty-three percent of patients developed platelet counts of less than or equal to 50,000/microL, and 36% of the total group required platelet transfusions. Mild neutropenia and a rebound lymphocytosis followed discontinuation of IL-2 treatment. To explore the possible mechanisms for these hematologic effects, standard hematopoietic colony assays were conducted on serial blood samples from five patients. IL-2 produced a significant decline in circulating erythroid (BFU-E) and granulocytic/macrophage (CFU-C) progenitors, which rebounded after the discontinuation of IL-2 therapy. Infusion of IL-2 also resulted in measurable serum levels of gamma-interferon. Some of the hematologic effects of immunotherapy with LAK cells and IL-2 may be the result of IL-2-mediated suppression of hematopoiesis.

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