ABSTRACT
The effect of acute heat stress on certain immunological parameters were studied in male albino rats. The test rats were exposed to an ambient temperature of 40 degrees celsius for 30 minutes and sacrificed immediately. Total WBC count, Differential count, Phagocytic index, NBT reduction, organ weight body weight ratio of spleen, thymus, and popliteal lymph nodes, and soluble immune complex levels were measured in control group and the heat stressed animals. The heat stressed animals show decrease in total WBC count, and neutrophilia, eosinophilia, and lymphocytopenia. The phagocytic index showed a significant increase whereas the avidity index showed a decrease from the control value. NBT reduction was also significant. The soluble immune complex level was not altered. The heat stressed animals showed a decrease in the thymus and spleen weight/body weight ratio while the lymph node/body weight ratio showed an increase compared to the control animals.