REGULATION OF MACROPHAGE FUNCTION BY HUMAN RECOMBINANT MYELOPEROXIDASE

Myeloperoxidase is an enzyme which is found in the azurophilic granule s of neutrophils and is, associated with bactericidal, fungicidal, and tumoricidal activity. The present studies show that human recombinant myeloperoxidase (rec-MyPo) can regulate a number of macrophage (Mphi) capacities and functions. Macrophages from mice exposed to rec-MyPo i n vitro released reactive oxygen intermediates, tumor necrosis factor alpha (TNFalpha), and interferon alpha/beta (IFNalpha/beta). Enhanced target cell killing was also demonstrated with TNFalpha sensitive but not TNFalpha insensitive cells. Intravenous injection of rec-MyPo indu ced high titers of systemic TNFalpha and IFNalpha/beta. These results indicate that MyPo can function as an immunomodulator both in vitro an d in vivo. Because of these actions, it is apparent that MyPo represen ts a previously unrecognized endogenous immunomodulator.