The effect of sodium nitrite on some parameters of the immune system.

The effect of orally administered sublethal doses of 25, 50 and 100 mg/kg of sodium nitrite in drinking water ad lib. for 21 days on the immune response of Balb/c mice was investigated. The immunological parameters were examined at three phases: 1 day (phase A), 1 week (phase B) and 3 weeks (phase C) after the end of exposure to sodium nitrite. A significant decrease in dose-dependent manner was obtained in the following tests: lymphocyte percentages, concanavalin A (Con A)- and lipopolysaccharide (LPS)-induced lymphocyte proliferation assessed by the colorimetric MTT method, natural killer (NK) cell activity against WEHI-164 target cells, as well as IgM and IgG titers against injected sheep erythrocytes. Maximum suppressions were obtained in phase A after treatment with sodium nitrite at 100 mg/kg including lymphocyte count (17.5%), Con A-induced lymphocyte proliferation (40.1%), LPS-induced lymphocyte proliferation (31.4%), IL-2-stimulated NK cell activity (59.2%), unstimulated NK cell activity (59.6%), IgM titer (57.5%) and IgG titer (61.1%). On the other hand, a significant dose-dependent increase in neutrophil count (71.3%) in phase A and phagocytic activation (133%) in the first two phases was obtained using the nitroblue tetrazolium (NBT) assay in the presence of phorbol myristate acetate (PMA). It was found that the immunosuppressive effect of sodium nitrite is reversible after cessation of exposure.