| The small intestine is of great significance for the growth of poultry. This organ is not only the major sites for digestion and absorption but also an active component of the mucosal immune system, playing an important role in immunity. Following ingestion of AFB1-contaminated food or feed, the intestine could be exposed to a high concentration of toxin. AFB1 would have an adverse effect on the small intestine. Up to now, people have paid attention to the studies on the toxicity of AFB1, and researches on these branches have made certain progress. However, limited information is available concerning the influence of AFB1 on the intestinal mucosal immunity by dietary AFB1. In this study, one hundred and fifty six one-day-old healthy Cobb broilers were randomly divided into control group (0 mg/kg AFB1) and AFB1 group (0.6 mg/kg AFB1) with six replicates per group for 21 days. The aims of the present study were to investigate the effects of 0.6 mg/kg dietary AFB1 on the dynamic changes in the intestinal mucosal immune related factors in broilers'small intestine by light and electron microscopes, flow cytometry (FCM), immunohistochemical staining and quantitative real-time PCR (qRT-PCR) techniques. The effects of AFBi on the intestinal mucosal immune function and its mechanism in broiler were discussed. Research results are as follows:When compared with the control group, the significant decreases of broilers'body weight in the AFB1 group at 7,14 and 21 days of age were noted (p<0.01 or p<0.05). Under the light and electron microscopes, the intestinal villi of the duodenum, jejunum and ileum in the AFB1 group were shedding. The microvilli of absorptive cells were also shedding in which the mitochondrial cristae were broken and its contents were disappearing. The electron density of the absorptive cells was decreased. The cell connections between the mucosa epithelial cells were irregular.When compared with the control group, the villus height and villus/crypt ratio in the AFB1 group of duodenum, jejunum and ileum were significantly decreased at 7,14 and 21 (p<0.01 or p<0.05) days of age, and crypt depth was significantly increased (p<0.01 or p<0.05) (except for the villus height in the duodenum and jejunum at 7 days, and the villus height in the ileum at 7 and 14 days as well as villus/crypt ratio and crypt depth in the duodenum and ileum at 7 days). The significant decreases of the number of goblet cells in the AFB1 group were observed in the three intestinal segments (p<0.01 or p<0.05) during the experiment (except for duodenum and ileum at 7 days)The results of flow cytometry showed that compared with the control group, the percentages of CD3+ LPLs in the AFBi group were significantly decreased in the duodenum at 14 and 21 days of age (p<0.05) and the percentages of CD3+CD4+IELs and LPLs in the AFB1 group significantly decreased at 14 and 21 days of age (p<0.01 or p<0.05). Furthermore, the percentages of CD3+CD8+IELs and LPLs were significantly decreased at 21 days of age (p< 0.01 or p<0.05). The changing pattern of the percentages of CD3+? CD3+CD4+ and CD3+CD8+ in the IELs and LPLs of jejunum and ileum in the AFB1 group were similar to that of duodenum, showing a decreased tendency in comparison to the control group.Real-time PCR analysis indicated that the mRNA expression levels of IL-2, IL-4, IL-6 and TNF-a mRNA in the AFB1 group were significant decreased in the ileum at 7,14 and 21 days of age (p< 0.01 or p<0.05) except for the IL-2 at 7 days of age, and in the duodenum and jejunum at 14 and 21 days (p< 0.01 or p<0.05) in comparison to the control group. The significant decreases of IL-10 mRNA expression levels in the AFB1 group were observed in the three intestinal segments at 21 days of age (p<0.01), and in the ileum at 14 and 21 days (p< 0.01 or p<0.05). The IL-17 mRNA expression levels in the AFB1 group presented dramatic decline in the duodenum and ileum at 14 and 21 days of age (p< 0.01 or p<0.05), and in the jejunum at 7,14 and 21 days of age (p< 0.01 or p<0.05). The significant decreases of the IFN-y mRNA expression in the AFB1 group were seen in the duodenum at 7,14 and 21 days of age, and in the jejunum at 21 days, and in the ileum at 14 and 21 days of age (p< 0.01 or p<0.05). When compared with the control group, the expression levels of pIgR, IgM, IgA and IgG mRNA were significantly decreased in the three intestinal segments of the AFBi group during the experiment (p<0.01 or p<0.05) (except for IgA mRNA in the duodenum at 7,14 days and in the jejunum at 7 days, and pIgR and IgM mRNA in the duodenum and jejunum at 7 and 14 days as well as IgG mRNA in the duodenum at 7 and 14 days and in the ileum at 7 days).A significant decrease in the number of IgA+ cells in the duodenal, jejunal and ileac mucosa in the AFB1 group were observed at 14 and 21 days of age (p< 0.01 or p<0.05) in comparison to the control group.In conclusion:dietary 0.6 mg/kg AFB1 inhibited the growth and development of broiler. It caused the pathological injury of duodenum, jejunum and ileum. It also lead to the decreases in the number of IgA+cells, the expression levels of IgA, pIgR, IgM and IgG mRNA, the percentages of CD3+, CD3+CD4+ and CD3+CD8+T-cell subsets in IELs and LPLs as well as the expression levels of IL-2, IL-4, IL-6, IL-10, IL-17, IFN-? and TNF-?mRNA in the duodenum, jejunum and ileum. These results suggested that the mucosal immune function of broiler's small intestine might be affected. |
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