The diffusely-infiltrated lymphoid tissue of the bursa of fabricius of Sturnus unicolor. Histological organization and functional significance

Abstract

In the present study we confirm and extend previous reports about the existence of a T-dependent area in the bursa of Fabricius of some birds, analyzing ultrastructurally the cell content of the so-called diffusely-infiltrated lymphoid tissue of the bursa of the spotless starling, Sturnus unicolor. I t consists of lymphocytes, plasma cells, macrophages (MW) and interdigitating cells (IDCs) in a supporting reticular stroma which, apart from blood capillaries, contains postcapillary high-endothelial venules (HEVs). The presence of both IDCs and HEVs confirms the T-celldependent nature of this area, as previously claimed for other avian species, and emphasizes other functions. apart from its role in B-cell maturation, for the bursa of Fabricius specially in adult birds.