The Protective Effects Of Sodium Selenite On Immune Organs In AFB₁-poisoned Chicken

Three hundred1-day-old Avain broilers, divided into five groups, were fed with control group diet (containing0.404mg/kg Se determined by Atomic absorption spectrophotometry), AFB1group diet (0.3mg/kg AFB1) and+Se group diets (0.2,0.4, and0.6mg/kg Se as sodium selenite were supplemented in the AFB1group diet to compound+Se groups Ⅰ, Ⅱ and Ⅲ diets, respectively) for21days. For investigating the effects of Se counteracting the toxicity of AFB1on immune organs, histopathology, biochemistry, flow cytometry and ELISA method were used. Results as follow:Thymus:The relative weight of thymus in AFB1group, compared with control group, was decreased. Histopathologically, the major lesions of thymus included congestion in medulla and a lot of debris in cortex in AFB1group. It was observed in AFB1group that the percentage of apoptotic thymocytes detected by TUNEL assay and FCM was increased, and the contents of Caspase-3and Bax expression were increased, while the content of Bcl-2expression was decreased. The percentages of mature thymocytes, CD4+CD8-and CD4-CD8+T cells, in AFB1group were lower than those in control group. Moreover, the percentages of peripheral blood CD3+, CD3+CD4+, CD3+CD8+and the contents of serum IL-2and IFN-y in AFB1group were decreased, compared with those in control group. Sodium selenite supplied in the diet, compared with AFB1group, could increase the relative thymus weight alleviate lesions, reduce the incidence of apoptotic thymocytes, increase percentages of mature thymocytes and peripheral blood T-cell subsets, and increase the contents of serum IL-2and IFN-γ.Spleen:The relative weight of spleen in AFB1group was lower than that in control group at21days of age. The major histopathological lesions of spleen included congestion in red pulp and vacuoles appeared in periarterial lymphatic sheath in AFB1group. Through FCM, the percentages of CD3+, CD3+CD4+and CD3+CD8+T cells in AFB1group were lower than those in control group. AFB1, by biochemical approaches, significantly decreased the activities of glutathione peroxidase, total superoxide dismutase, glutathione reductase, catalase and the level of glutathione hormone, while increased the level of malondialdehyde. Moreover, AFB1increased the percentage of apoptosis cells by flow cytometry and the occurrence of apoptotic cells by TUNEL assay. Compared with AFB1group, supplementing with sodium selenite could increase the relative spleen weight, alleviate the lesions of spleen, inhibite oxidative stress and excessive apoptosis, and increase percentages of splenic T cell subsets.Bursa of Fabricius:Compared with control group, the relative weight of bursa of Fabricius in AFB1group was decreased. By histopathological observation, the major lesions in AFB1group were increased number of vacuoles and debris in the lymphoid follicle. The percentages of apoptotic cells in the bursa of Fabricius detected by Tunel and FCM in AFB1group were higher than those in control group. Although the contents of Bax and Bcl-2expression were so low that it could not be for statistical treatment, by immunohistochemistry, the content of Caspase-3expression was higher than that in control group.The contents of IgA, IgG and IgM in serum, by the meas of ELISA, in AFB1group were lower than those in control group. Compared with AFB1group, the supplementation of sodium selenite in the diet alleviated the suppression of bursal development and lesions in bursa of Fabricius, decreased excessive apoptosis and increased the contents of immune globulins in serum.Conclusion:The sodium selenite supplied into the dietary containing0.3mg/kg AFB1could alleviate the lesions in thymus, spleen and bursa of Fabricius, decrease the percentages of apoptotic cells, and increase the percentages of mature T cells in thymus, spleen and peripheral blood. Through increasing the contents of serum IL-2,IFN-y, IgA, IgG and IgM, sodium selenite could relieve the depression of cellular and humoral immunity, which may result from regulation on antioxidant and apoptosis. According to this research, the optimal effects against0.3mg/kg AFB1were exerted by0.804mg/kg Se in the dietary.