Abstract: The study aimed to investigate the effects of avian reticuloendotheliosis virus (REV) on the number of T lymphocytes in blood and the expression of related cytokines in local lymphoid tissues of SPF chicks. Ninety-six 1-day-old SPF chicks were randomly divided into REV-infected group and control group. The above indexes were detected by Flow Cytometry, acid α-naphthyl acetate esterase (ANAE) and Quantitative Real-time PCR. The results showed that compared with the control group, the number of CD4⁺ T lymphocytes in the infected group was significantly decreased at day 7-35, and the number of CD8⁺ T lymphocytes was significantly increased at day 7-28, the CD4⁺/CD8⁺ ratio was significantly decreased at day 7-28 (all P<0.05 or P<0.01); the number of ANAE⁺ T lymphocytes in the local lymphoid tissues of Hader's gland (HG), Peyer's patch (PP) and caecal tonsil (CT) were significantly decreased (all P<0.05 or P<0.01); the transcription levels of cytokines IL-2, IFN-γ and TNF-α in HG, PP and CT were increased in various degrees. These data indicated that REV infection caused a decrease in the number of CD4⁺ T lymphocytes in the peripheral blood of chickens, an imbalance of the ratio of CD4⁺/CD8⁺ T lymphocytes, a relative decrease in the number of T lymphocytes in local lymphoid tissues, and a continuous increase in the expression of cytokines TNF-α are closely related to the significantly reduced cellular immune function of infected chickens caused by REV.

Key words: reticuloendotheliosis virus, local lymphoid tissue, cellular immunity