EFFECTS OF OCHRATOXIN-A ON THE MOUSE IMMUNE-SYSTEM AFTER SUBCHRONIC EXPOSURE

The effects on the immune system of oral, subchronic exposure to ochra toxin A (OA) at 6, 250 or 2600 mu g/kg diet were studied in female Bal b/c mice. After 28 days of exposure, antibody production to sheep red blood cells, as measured in the plaque-forming cell assay and expresse d as number of plaque-forming cells/spleen, was suppressed in a dose-d ependent manner which was significant in the two highest exposure grou ps. In addition, a decrease in thymocyte cell counts was seen in thee 250-mu g/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 responsiv eness of thymocytes and splenocytes to concanavalin A (Con A) was sign ificantly decreased. This effect was observed in all three treatment g roups. Interleukin-2 production of Con A-stimulated lymphocytes, natur al killer cell activity, and humoral antibody titres to a viral antige n were not affected by OA treatment. The present results indicate that subchronic, oral exposure to OA affects certain immune functions in m ice at exposure levels that may be found in contaminated food products .