Effect And Mechanism Of Quercetin On Immune Function In AA Broilers

240 Arbor Acre?AA?male broilers?1 day old,healthy?were randomly divided into 4 groups,with 6 replicates per group and 10 broilers per replicate.The control group was fed with basal diet,and the treatment groups were fed with basal diet supplemented with 0.02%,0.04%,and 0.06%of quercetin for 42 days.In this study,immune organ index,content of serum immunoglobulin,complements,cytokine and expression of immuno-related genes were determined to investigate the mechanism of quercetin regulating immune function in AA broilers.Effect of quercetin on immune organ index in AA broilers:compared with control,spleen index and thymus index were significantly increased by supplementation of quercetin at 0.06%,however,there were no significant difference in bursa of fabricius indexes?P>0.05?.Effect of quercetin on humoral immunity in AA broilers:compared with control,content of serum IgA was significantly increased in the 0.04%quercetin group?P<0.05?and the 0.06%quercetin group?P<0.01?,respectively.Content of serum IgM of the 0.06%quercetin group was significantly increased?P<0.05?.However,the content of serum IgG was not significantly increased with increasing quercetin?P>0.05?.Content of serum C₃ was significantly increased in the 0.02%quercetin group?P<0.05?.Both 0.04%and 0.06%quercetin significantly increased content of serum complement C₄?P<0.01?.Content of serum IL-2 was significantly increased in the 0.04%quercetin group?P<0.05?,and content of serum IL-4 was significantly increased in the0.06%quercetin group?P<0.01?.Content of serum IFN-gamma was significantly increased in the0.06%quercetin group?P<0.05?.Effect of quercetin on cellular immunity in AA broilers:compared with control,conversion rate of splenic lmphocyte were significantly increased with increasing quercetin?P<0.01?.However,content of T lymphocyte subgroup CD4 and CD8 was not significantly affected by three levels of quercetin?P>0.05?.Effects of quercetin on expression of immuno-related genes associating with NF-kappa B signaling pathway in AA broilers:0.04%and 0.06%quercetin significantly increased mRNA expression of tumour necrosis factor-alpha,tumor necrosis factor receptor related factors-2,tumor necrosis factor receptor superfamily1B and nuclear transcription factor-kappaB protein 65 as compared to control?P<0.01?,and mRNA expression of inhibitor kappaB-alpha was significant decreased in spleen?P<0.01?.mRNA expression of interferon-gamma of spleen was significantly increased in the 0.06%quercetin group?P<0.01?.Both of 0.02%and 0.06%quercetin significantly increased mRNA expression of nuclear transcription factor-kappaB protein 65 mRNA and significantly decreased mRNA expression of tumor necrosis factor receptor superfamily1B and inhibitor kappaB-alpha in thymus?P<0.05?.mRNA expression of the interferon-gamma in the0.04%quercetin group was significantly increased in thymus.mRNA expression of tumour necrosis factor-alpha,interferon-gamma,tumor necrosis factor receptor superfamily1B and inhibitor kappaB-alpha were significantly increased by 0.02%and 0.04%quercetin?P<0.01?,nevertheless,mRNA expression of tumour necrosis factor-alpha,tumor necrosis factor receptor superfamily1B,inhibitor kappaB-alpha and tumor necrosis factor receptor related factors-2 were significantly increased by the 0.06%quercetin in bursa of fabricius?P<0.01?.In conclusion,dietary supplementation of quercetin at different levels improved development of immune organs and promoted secretion of immunoglobulin,complement,interleukin,and interferon in AA broilers.Thus,quercetin improved immune function and its regulatotion may be accomplished via NF-kappa B signaling pathway.