In vitro restoration by interleukin-2 (IL-2) of the impaired natural killer cell activities, IL-2 receptor expression, and T cell proliferation in hemophilia.

Five of 22 hemophiliacs who were seropositive for human T cell leukemia virus III (HTLV III) and manifested severe impairment of immune parameters (both in vivo and in vitro) similar to those observed in patients with clinical symptoms of acquired immune deficiency syndrome (AIDS) were chosen for this study. Profound lymphopenia was observed in four of five patients with decreased and qualitatively impaired helper/inducer (T4) cells and increased T suppressor/cytotoxic (T8) cells. Observed in all patients was impaired endogenous production of interleukin-2 (IL-2), expression of the IL-2 receptor combined with diminished responses to mitogens, mixed leukocytes reaction (MLR), and natural killer (NK) reactivity. In vitro supplement of exogenous IL-2 markedly augmented T and NK cell functions, as well as the expression of activation antigens on both T4 and T8 cell in four of five patients. Our findings suggest that a substantial proportion of this cell-mediated immunologic defect in hemophiliacs stems from their inability to produce adequate amounts of IL-2. Interleukin-2 may therefore have the potential for therapy as an immune response modifier in patients with hemophilia by providing beneficial preventive therapy for patients at risk.