Elevated production of interleukin-2 by lymphocytes from children with acute leukemia.

Abnormalities of the production of interleukin-2 (IL-2) may play an important role in the immunologic dysfunction observed in pediatric leukemia patients. For an evaluation of the ability of lymphocytes from leukemic children to produce this cytokine, the production of IL-2 by mitogen-stimulated peripheral blood mononuclear cells was determined in children with acute leukemia at the time of diagnosis, during clinical remission, and at the time of relapse. Of 16 patients, 11 (69%) with either acute lymphoblastic leukemia or acute nonlymphoblastic leukemia at the time of diagnosis had IL-2 production levels above the highest level observed in control subjects, and all but one had values above the control mean. Three of five treated patients had elevated IL-2 production at the time of bone marrow relapse. In addition, of 37 patients examined during clinical remission (both during chemotherapy and after the completion of maintenance chemotherapy), five had IL-2 production values above the control range and four of these five patients subsequently had relapses, compared with only one relapse in the remaining 32 patients with normal or below-normal levels of IL-2 production. These results demonstrate an increased ability to produce IL-2 by many patients with acute leukemia, both at the time of diagnosis and at relapse. Elevated IL-2 production may represent an immunologic response to leukemic cells and in some patients may provide a marker for persistent leukemia.