Endogenous oncornaviral antigen in the bursa of Fabricius of 15B X 7(2) chickens.

Oncornaviral antigen was detected in the bursal epithelium and in a subpopulation of bursal follicular cells of 15B X 72 chickens. This antigen is present in the bursal epithelium at 11 days of embryogenesis and persists there for at least 3 weeks after hatching. The absence of detectable antigen in the intestinal epithelium contiguous to the bursal epithelium indicates that the accumulation of viral antigen is a specific property of the bursal epithelium. The observation of C-type particles in the intraepithelial spaces suggests that the viral antigen in synthesized and assembled into virions by the bursal epithelial cells. In embryonic bursas, viral antigen-positve cells radiate from the surface epithelium toward the central region of the follicles. In bursas from post-hatch chickens, viral antigen-positive cells, including intrafollicular epithelial cells and cells resembling lymphocytes, are confined to the medullary region of the follicles.