Functional alterations of human blood monocytes after exposure to various nickel compounds in vitro: an effect on the production of hydrogen peroxide.

It is generally known that nickel, a metal with distinct carcinogenic properties, can significantly alter the functioning of host defense mechanisms and impair various components of the immune system. In the present study the influence of 3 nickel salts on the production of hydrogen peroxide (H2O2) by human monocytes was examined in in vitro culture. Highly purified, resting and PMA-stimulated normal human monocytes were cultured with subtoxic concentrations of nickel subsulfide nickel sulfate, nickel acetate and manganese chloride. A portion of the cells was cultured with nickel-manganese salt mixture. Following culture cells were tested in an in vitro functional assay for H2O2 production. It has been shown that all nickel salts, used in micromole concentrations, suppressed H2O2 formation both in resting and PMA-stimulated monocytes, while it was not the case when manganese chloride was used for cell cultures. The strongest suppressive effect was manifested by nickel sulfate. The cells subjected to nickel-manganese mixture displayed H2O2 production similar to that of control ones. These results show that nickel salts in micromole concentrations exert a suppressive effect on oxygen-dependent antimicrobial system of human monocytes and manganese prevents this effect.