The characterization of an Fc receptor cell population in the maturing bursa of fabricius

Abstract An antibody-coated erythrocyte assay was used to identify the presence of cells with Fc receptors (FcR) within the bursa of embryonic chicks. The greatest percentage of FcR cells was found at 16 days and from then on there was a steady decrease until hatching. Organ culturing of 16-day embryonic bursae resulted in an increase in the percentage of FcR cells and the percentage was further increased when T-cell mitogens were added to the organ cultures. Using cell separation procedures, detection of surface immunoglobulin, and staining for nonspecific esterase indicated the FcR cells were not B cells but most likely macrophages. When embryonic bursal cells were tested for fibronectin-mediated phagocytosis, we observed cells which were able to ingest gelatin-coated latex. We conclude that the FcR cell population in the embryonic bursa consists primarily of monocytic macrophages.