Probiotic feeding affects T cell populations in blood and lymphoid organs in chickens

This study was performed to evaluate the effects of Lactobacillus acidophilus bacteria as a probiotic on chicken T cell subset populations in peripheral blood and lymphoid tissues. Thirty chickens were divided into three groups and fed sterilised cow milk, a mixture of milk and L. acidophilus (probiotic), or neither, as the control group. Chickens were euthanised after 14 and 21 days, and whole blood and ileal, bursal, and caecal tonsillar tissues were collected. The populations of T cell subsets, including CD4⁺, CD8⁺, and TCR1⁺ cells, were evaluated by immunohistochemistry and flow cytometry. After 21 days of treatment the percentage of blood CD4⁺, CD8⁺, and TCR1⁺ cells was significantly higher in the probiotic-fed group than in the control group. After 14 days of treatment, a significantly greater number of CD4⁺ T cells were found in the ileum of probiotic-fed chickens than in chickens from the other two groups. This difference was even greater after 21 days. In addition, after 21 days, a significantly greater number of TCR1⁺ cells were found in the caecal tonsils of milk-fed chickens than in chickens from the control group. The findings indicate that probiotics may alter the distribution of T cells in the blood and lymphoid tissues in young chickens; however, transient changes in lymphoid tissues indicate that probiotics likely do not permanently affect mucosal immunity.