Effects of ochratoxin a on the mouse immune system after subchronic exposure

The effects on the immune system of oral, subchronic exposure to ochratoxin A (OA) at 6, 250 or 2600 μg/kg diet were studied in female Balb/c mice. After 28 days of exposure, antibody production to sheep red blood cells, as measured in the plaque-forming cell assay and expressed as number of plaque-forming cells/spleen, was suppressed in a dose-dependent manner which was significant in the two highest exposure groups. In addition, a decrease in thymocyte cell counts was seen in the 250-μg/kg group. After 90 days of exposure, flow cytometry analysis of thymic lymphocyte subpopulations revealed a decreased proportion of mature (CD4+ or CD8+) cells. Furthermore, the mitogenic responsiveness of thymocytes and splenocytes to concanavalin A (Con A) was significantly decreased. This effect was observed in all three treatment groups. Interleukin-2 production of Con A-stimulated lymphocytes, natural killer cell activity, and humoral antibody titres to a viral antigen were not affected by OA treatment. The present results indicate that subchronic, oral exposure to OA affects certain immune functions in mice at exposure levels that may be found in contaminated food products.