Dynamic Changes in the Intraepithelial Lymphocyte Numbers Following Salmonella Typhimurium Infection in Broiler...

At day 21 of age, Ross-308 broilers were orally gavaged with 7.5 × 10⁶ CFU/mL S. Typhimurium (n = 30), and another 30 birds were kept as the control. The body weight of birds was recorded on days 0, 2, 7, and 14 days post-infection (dpi) to calculate body weight gains (BWGs). At each time point, seven birds per group were euthanized for sample collection to acquire IELs and lymphocytes from the ileum and spleen for flow cytometric analysis. A reduction in BWGs of the infected groups compared to the control group was observed only at 2 dpi. Additionally, there were no changes in the expression of IFN-γ, IL-1β, and TNF-α in the ileum at 2 and 7 dpi. The number of IELs increased significantly following Salmonella infection in the ileum at 2 and 7 dpi without any changes in spleen lymphocytes. The increase in the total number of IELs was derived from the elevated numbers of conventional CD8αβ⁺TCRαβ⁺ and natural IEL populations (CD4^-CD8^-TCRαβ⁺, CD8αα⁺TCRαβ⁺, TCRγδ⁺, non-T cells (TCR^neg, and iCD8α cells)). The increase in regulatory IELs and the stable expression of proinflammatory cytokine genes during the first week of infection suggests the potential role of IELs in modulating intestinal inflammation.