Effect Of Methionine Deficiency On Immune Organs And Immune Function In Broilers Wu Bang-yuan (Basic Veterinary) Directed By Cui Heng-min And Fang Jing

120 one-day-old Avian broilers were randomly divided into two groups with 6 replicates each and 10 broilers in each replicate. One replicate was used for the full range observation in the experiment. Broilers were fed on a control diet (starter diet, methionine 0.50%; grower diet, methionine 0.40%) or methionine deficient diet (starter diet, methionine 0.26%; grower diet, methionine 0.28%) and were provided with water as well as aforementioned diets ad libitum for 42 days. The sampling time points was 14.28, 42 days of age. The experiment was conducted with the objective of examining the impact of methionine deficiency on immune function in broilers by methods of experimental pathology and flow cytometry (FCM). Results were as follows:Thymus:Lymphocytes in medulla of thymic lobule were remarkably decreased in number or/and loosely arranged in methionine deficiency. The frequency of lymphocyte apoptosis was higher in methionine deficiency than in control group. The statistical analyses by FCM indicated that the Go/G1 phase of thymocyte were increased and the G2+M phase, S phase of thymocyte and the PI were decreased (P＜O.01) in methionine deficiency. Meanwhile, the percentage of cellular apoptosis was higher in methionine deficiency than in control group (P<0.01). Also, the TUNEL staining was consistent with the result of FCM, more apoptosis lymphocyte can be seen in the section.Bursa of Fabricius:From 28 days of age to the end of the experiment, the lymphocytes were decreased in lymphoid follicles with thinner cortex and wider medulla, and the pathology was more obvious with the increased age. Ultrastructurally the mitochondria were swelled and mitochondria cristas were broken and the frequency of lymphocyte apoptosis was higher in methionine deficiency than in control group. The statistical analyses by FCM indicated that the G0/G1 phase was increased and the G2+M phase, S phase and the PI were decreased (P<0.01) in bursa of Fabricius in methionine deficiency at 28 and 42 days of age, Meanwhile, the percentage of cellular apoptosis was higher in methionine deficiency than in control group. Also, the TUNEL staining was consistent with the result of FCM, more apoptosis lymphocyte can be seen in the section.Spleen:The lymphocytes were significantly decreased in white pulp and red pulp in Met deficiency, and the histological structure of spleen was disordered in Met deficiency; Ultrastructurally, the frequency of lymphocyte apoptosis was higher in methionine deficiency than in control group. The mitochondria were swelled or vacuolated with degenerating cristae. The statistical analyses by FCM indicated that the G0/G1 phase were increased and the G2+M phase, S phase and the PI (Proliferating index) were decreased in methionine deficiency. Meanwhile, the percentage of cellular apoptosis was higher in methionine deficiency than in control group. Also, the TUNEL staining was consistent with the result of FCM, more apoptosis lymphocyte can be seen in the section. The splenic superoxide dismutase (SOD) and glutathion peroxidase (GSH-Px) activities were decreased (P＜0.01), and the glutathione (GSH) contents were significantly lower (P＜0.05 or P＜0.01) in Met deficiency than in control group, the malondialdehyde (MDA) contents were increased (P<0.01) in methionine deficiency compared with those of the control group. At the same time, the abilities to inhibit hydroxyl radicals were greatly decreased in methionine deficiency.The activities of SOD and GSH-Px in serum were decreased, and the glutathione (GSH) contents were decreased, malondialdehyde (MDA) contents were increased (P<0.01) and the abilities to inhibit hydroxyl radicals were greatly decreased in methionine deficiency compared with those of the control group. The percentages of CD3+, CD3+CD4+and CD3+CD8+were decreased in methionine deficiency in varying degrees, and the ratio of CD4+/CD8+was decreased; The stimulation index (SI) of peripheral blood T-cells were lower in Met deficiency than in control group; Also, the serum interleukin-2 (IL-2) contents were decreased in methionine deficiency (P＜0.01); The detection by immunoturhidimetry indicated that the serum IgG, IgA and IgM contents were much lower (P<0.01) comparison with those of control group.It was concluded that①the percentages of the peripheral blood T-cell subsets were influenced by methionine deficiency in diet. The ratio of CD4+and CD8+T cells was decreased. They could influence the biological function of mature T lymphocytes, which showed the inhibition of cellular immune fuction.②The decreased contents of serum immunoglobulin (IgG,IgA,IgM) showed that the function of B lymphocytes was influenced, which would lead to further impact on humoral immune function.③The decreased activities of antioxidase (SOD,GSH-Px),and increased products of lipid peroxidation (MDA) and the abilities to inhibit hydroxyl radicals decreased,which caused oxidative damage in spleen.④Methionine deficiency intake inhibited the proliferation and development of lymphocytes in immune organs (Thymus, Bursa of Fabricius and Spleen) and increased the population of apoptotic lymphocytes, which finally led to inhibition on the development of immune organs and impaired the immune function in chickens.