In vitro lymphoproliferative responses of peripheral blood mononuclear cells of cadmium chloride exposed indian catfish (Clarias batrachus), treated with different antioxidants
The immunomodulatory effect of three antioxidants viz. Vitamin C, Garlic extract and Taurine was evaluated in the cadmium chloride exposed Indian catfish (Clarias batrachus). For this, experimental fishes were divided randomly into nine equal groups (I-IX; n=50) and kept in separate plastic pools (capacity of 500 L). The fishes of groups II, III, IV and V; and VI, VII, VIII and IX were exposed to 5 and 10 ppm solution of CdCl2 (bath treatment), respectively, for an observation period of 45 days. Simultaneously, these CdCl2 exposed fishes were treated with the three antioxidants: Groups III and VII, IV and VIII, V and IX were bath treated with vitamin-C (5 ppm), extract of dried garlic (5 ppm) and taurine (5 ppm), respectively, starting from the day 1 of CdCl2 exposure till the end of the experiment. Group II and VI were maintained as cadmium exposed non-treated controls, while the Group I was kept as negative control (without exposure to CdCl2). For evaluating the immunomodulatory effects of the three antioxidants, five fish form each group were scarified and the blood samples collected aseptically from caudal vein on 15th, 30th and 45th day of exposure and/or treatment for the isolation of peripheral blood mononuclear cells (PBMCs). In vitro, non-specific stimulation of the PBMCs of all the experimental groups of fishes was done with Concanavalin A (Con-A) (10 μg/ml) and Phytohaemagglutinin - P (PHA-P) (10 g/ml) and lymphocyte proliferation activity assessed by the lymphocyte transformation test (LTT). Stimulation indices (SI) values from CdCl2 exposed catfish showed significant (P<0.05) suppression in lymphocyte proliferation compared to control group, while all the antioxidant treated groups revealed significant (P<0.05) inhibition of the suppression of the lymphocyte blastogenesis. At 45 day, SI values of 0.83±0.02 and 0.088±0.01; and 0.67±0.02 and 0.71±0.02 were observed in 5 ppm and 10 ppm CdCl2 exposed groups with ConA and PHA-P, respectively. Significant SI values of 0.81±0.00 and 0.87±0.01; 0.74±0.01 and 0.81±0.02; 0.71±0.01 and 0.78±0.01 were observed in the vitamin-C, garlic extract and taurine treated groups at 45 days with Con-A and PHA-P, respectively. The PBMCs of the fishes exposed to Cadmium at a lower dose @ 5 ppm responded comparatively better to these mitogenic stimulants in terms of lymphoproliferative responses. In conclusion, the study highlights the cell mediated immunomodulatory property of the vitamin C, garlic extract and taurine against the Cadmium toxicity in fish.