An immunohistochemical analysis of T-cell subsets in the chicken bursa of Fabricius during postnatal stages of development.

T-cell subsets in the chicken bursa of Fabricius were analysed immunohistochemically during postnatal stages. Distinct types of T cells were present both in the surface epithelium and lamina propria of the bursa. TcR1+ and CT8+ cells were predominant in the surface epithelium, while TcR2+ and CT8+ cells were numerous in the lamina propria. These T-cell subsets peaked in frequency of occurrence at 5 weeks. They then decreased in number, and a few T cells remained in the bursa until 15 weeks of age. This result showed that the bursa of chickens is furnished with the distinct types of T-cell subsets at early postnatal stages of development to maintain its local immunity.