CD4+CD25+ Regulatory T Cell Ontogeny and Preferential Migration to the Cecal Tonsils in Chickens

Thymic CD4+CD25+ cells have regulatory-T-cell-like properties in chickens. This study examined the ontogeny of CD4+CD25+ cells in the thymus and in peripheral compartments in chickens. CD4+CD25+ cells started to appear in the thymus at day 15 of incubation (E15), although at low percentages. Expressed as a percentage of CD4+ cells, CD4+CD25+ cells increased (P+CD25+ cells did not appear in the spleen or cecal tonsils of embryos. Expressed as a percentage of CD4+ cells, CD4+CD25+ cells increased (P+CD25+ cells than the spleen at D1. CD4+CD25+ cells from cecal tonsils of chicks at D1 were suppressive. CD4+CD25+ cells from D0 thymus, when injected back into MHC-compatible chicks, migrated to cecal tonsils and lungs and were detected until 10 d post-injection. CD4+CD25+ cells from cecal tonsils had a higher (P = 0.01) relative amount of CCR9 mRNA than CD4+CD25+ cells from the thymus. It could be concluded that in chickens CD4+CD25+ cells migrate from the thymus immediately post-hatch and preferentially colonize the gut associated lymphoid tissues. CD4+CD25+ cells' preferential migration to cecal tonsils is likely directed through the CCR9 pathway in chickens.