Regulation of CD4 + CD8 - CD25 + and CD4 + CD8 + CD25 + T cells by gut microbiota in chicken.

The gut microbiota in chicken has long been studied, mostly from the perspective of growth performance. However, there are some immunological studies regarding gut homeostasis in chicken. Although CD4 ⁺ CD25 ⁺ T cells are reported to act as regulatory T cells (Tregs) in chicken, there have been no studies showing the relationship between gut microbiota and Tregs. Therefore, we established a model for 'antibiotics (ABX)-treated chickens' through administration of an antibiotic cocktail consisting of ampicillin, gentamycin, neomycin, metronidazole, and vancomycin in water for 7 days. CD4 ⁺ CD8 ^- CD25 ⁺ and CD4 ⁺ CD8 ⁺ CD25 ⁺ T cells in cecal tonsils were significantly decreased in this model. Gram-positive bacteria, especially Clostridia, was responsible for the changes in CD4 ⁺ CD8 ^- CD25 ⁺ or CD4 ⁺ CD8 ⁺ CD25 ⁺ T cells in cecal tonsils. Feeding ABX-treated chickens with acetate recovered CD4 ⁺ CD8 ^- CD25 ⁺ and CD4 ⁺ CD8 ⁺ CD25 ⁺ T cells in cecal tonsils. GPR43, a receptor for acetate, was highly expressed in CD4 ⁺ CD8 ^- CD25 ⁺ T cells. In conclusion, our study demonstrated that the gut microbiota can regulate the population of CD4 ⁺ CD8 ^- CD25 ⁺ and CD4 ⁺ CD8 ⁺ CD25 ⁺ T cells, and that acetate is responsible for the induction of CD4 ⁺ CD8 ^- CD25 ⁺ T cells in cecal tonsils via GPR43.