This study was conducted to investigate the effects of AFB1 on T-cell subsets and cytokines mRNA expression in the small intestine of broilers.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 three replicates per group and 26 birds per replicate for 21 days,respectively.At 7,14,and 21 days of age,the duodenum,jejunum and ileum were sampled for analyzing T cell subsets(CD3+,CD3+CD4+and CD3+CD8+)by flow cytometry as well as IL-2,IL-4,IL-6,IL-10,IL-17,IFN-γ and TNF-α mRNA expression by qRT-PCR.The percentages of T-cell in the intra-epithelial lymphocytes(IELs)and lamina propria lymphocytes(LPLs)of duodenum,jejunum and ileum in the AFB1 group showed a decreased tendency in comparison to the control group.The mRNA expression of cytokines in the three intestinal segments in the AFB1 group presented a general decline compared with the control groups.Our data demonstrated that 0.6 mg/kg AFB1 in broilers diet could reduce the percentages of T-cell subsets and the expression level of cytokines mRNA in the small intestine,implying that the immune function of the intestinal mucosa might be impacted.The reduction of cytokines mRNA expression may be closely associated with the decreased proportions of T cells subsets induced by AFB1.