Journal of Leukocyte Biology 40:469-477 (1986) The Follicle-Associated Epithelium in the Bursa of Fabricius Cell Origin Studied by

The cell origin of the follicle-associated epithelium (FAE) of the bursa of Fabri-cius was studied by two different technical approaches. Precolonized quail bursal rudiments were grafted into chick embryos and the grafts were re-covered 2 wk after hatching of the recipients. By taking advantage of the distinct nuclear characteristics of chick and quail cells, it could be shown that the specialized FAE consists of a mixture of epithelial cells, with special features, among which hemopoietic cells, originating from the host, are dis-persed. Staining of chicken bursas with different monoclonal antibodies react-ing either with the epithelial component (BEP-1) or with the hemopoietic cells of the bursa (L22, L17) confirmed that hemopoietic cells, presumably macro-phages, are mixed with the epithelial cells at the level of FAE. Key words: grafts, macrophage