Cytokines affecting mononuclear phagocytes were screened for activation of human macrophages to secrete H2O2 and kill toxoplasmas. In contrast to recombinant interferon-gamma (rIFN gamma), the following factors, tested in partially or highly purified form and over a wide range of concentrations, did not augment these functions: native interferon-alpha (nIFN alpha), rIFN alpha A, rIFN alpha D, rIFN beta, colony stimulating factor (type 1) (CSF-1), CSF for granulocytes and macrophages (GM-CSF), pluripotent CSF (p-CSF), tumor necrosis factor (TNF), native interleukin 2 (nIL-2), and rIL-2. Partially purified migration inhibitory factor (MIF) enhanced H2O2-releasing capacity submaximally without inducing antitoxoplasma activity, and warrants further study.

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