THERAPY WITH OKT3 MONOCLONAL-ANTIBODY IN REFRACTORY T-CELL ACUTE LYMPHOBLASTIC-LEUKEMIA INDUCES INTERLEUKIN-2 RESPONSIVENESS

Administration of cytokines to patients with leukemia or lymphoma may recruit dormant malignant cells into cell cycle and thus make them mor e susceptible to chemotherapy. We treated a patient with refractory T cell acute lymphoblastic leukemia (ALL) with OKT3 monoclonal antibody and observed a dramatic but transient decrease of lymphoblasts. The T ALL cells were rather mature by morphology and immunophenotyping, expr essing CD7, CD4, CD8 and CD3 surface antigens and nuclear TdT. Cytogen etic analysis revealed inversion of chromosome 14(q11q32.1). A total o f 500 mg OKT3 (maximum dose 50 mg/day) was given. A decrease of lympho blasts in the blood and a reduction of spleen size was observed. Compl ement levels dropped remarkably. Despite increasing serum levels of tu mor necrosis factor, treatment was well tolerated overall. CD3 therapy induced strong IL-2 responsiveness of the lymphoblasts. Thus, OKT3 an tibody treatment not only significantly decreased CD3-positive tumor c ells, but also induced IL-2-mediated proliferation. This may also allo w sequential application of CD3 and IL-2 to render certain T cell tumo rs more susceptible to chemotherapy.