REGULATION OF MACROPHAGE FUNCTION BY HUMAN RECOMBINANT MYELOPEROXIDASE

Myeloperoxidase is an enzyme which is found in the azurophilic granules 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 in 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 induced high titers of systemic TNFalpha and IFNalpha/beta. These results indicate that MyPo can function as an immunomodulator both in vitro and in vivo. Because of these actions, it is apparent that MyPo represents a previously unrecognized endogenous immunomodulator.