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 more 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, expressing CD7, CD4, CD8 and CD3 surface antigens and nuclear TdT. Cytogenetic analysis revealed inversion of chromosome 14(q11q32.1). A total of 500 mg OKT3 (maximum dose 50 mg/day) was given. A decrease of lymphoblasts in the blood and a reduction of spleen size was observed. Complement levels dropped remarkably. Despite increasing serum levels of tumor necrosis factor, treatment was well tolerated overall. CD3 therapy induced strong IL-2 responsiveness of the lymphoblasts. Thus, OKT3 antibody treatment not only significantly decreased CD3-positive tumor cells, but also induced IL-2-mediated proliferation. This may also allow sequential application of CD3 and IL-2 to render certain T cell tumors more susceptible to chemotherapy.