INHIBITION OF MITOGEN-ACTIVATED PROLIFERATION OF HUMAN-LYMPHOCYTES BY HYPOCHLOROUS ACID INVITRO - PROTECTION AND REVERSAL BY ASCORBATE AND CYSTEINE

Hypochlorous acid (HOCl) at concentrations of 6.25 μM and greater caused statistically significant, dose-related inhibition of mitogen-activated proliferation of human mononuclear leucocytes (MNL). The anti-proliferative effects of HOCl, which were evident using both undepleted and adherent-cell depleten MNL, could not be attributed to decreased mitogen binding by HOCl-treated cells. The anti-oxidants ascorbate and cysteine (50 μM), when added to MNL prior to exposure to HOCl (25 μM), prevented the anti-proliferative effects of the oxidising agent. Likewise reversal of oxidant-mediated inhibition of the responsiveness of MNL to mitogens was observed when ascorbate and cystein were added after HOCl treatment of the cells. These results suggest that HOCl, derived from activated phagocytes, is a potential mediator of immunosuppression, especially in the setting of abnormal host anti-oxidant defences. © 1990 Birkhäuser Verlag.