The Effects Of Nickel Chloride On Thymic Immune Function In Broilers

Two hundred and eighty avian broilers were randomly divided into four groups and fed on a control diet (corn-bean basal diet) or diets supplemented with 300, 600 and 900 mg/kg nickel chloride (NiCl2) for 42 days. Samples were collected at 14, 28 and 42 days during the experiment. This study was conducted to observe the effects of NiCl2 on thymic immune function by methods of experimental pathology, flow cytometry (FCM), and quantitative real-time PCR (qRT-PCR) etc. Results were as follows:1. In comparison with the control group, broiler weight was slowly increased, and weight of thymus were reduced in the NiCl2 groups. Thymic corpuscles were increased and enlarged. The reticular cells were degenerate and necrotic, and lymphocytes were slightly decreased and loosely arranged in the medulla of thymus in the NiCl2 groups.2. Thymic SOD, and CAT, and GSH-Px, and content of GSH, and ability to inhibit hydroxyl radical were significantly decreased (P<0.05 or P<0.01) when compared with the control group) while contents of MDA was significantly increased.3. Results from FCM (Flow cytometry) showed that the percentages of thymocytes in G0/G1 phase were significantly increased (P<0.05 or P<001), and the percentages of thymocytes in S phase and proliferation index were significantly decreased (P<0.05 or P<0.01). The percentages of apoptotic thymocytes were significantly increased (P<0.05 or P<0.01). CD3+, CD3+CD4+, CD3+CD8+T lymphocyte percentage and CD4+/CD8+ratio were reduced in the NiCl2 groups in comparison with those in the control group.4. Results from qRT-PCR showed that the bax and caspase-3 mRNA expression levels and Bax/bcl-2 ratio were significantly increased (P<0.05 or P<0.01), and Bcl-2 mRNA expression levels was significantly decreased (P<0.05 or P<0.01) when compared with those in the control group. Also interleukin (IL)-1β, IL-2, IL-10, IL-12p35, IL-12p40, IL-21, TNF-a, IFN-y, thymosin p4, thymosin p10, thymosin β15 mRNA expression levels were down-regulated.The above-mentioned results showed that dietary NiCl2 in excess of 300 mg/kg groups could cause thymic abnormality as follows: ① oxidative damage, ② developmental inhibition, and ③ reduction of immune function.