Ultrastructural localization of a soluble antigen in the chicken Harderian gland

The relationship between plasma cells, macrophages, B and T cells, dendritic cells, and epithelium in the chicken Harderian gland have been studied by means of ultrastructural localization of the horseradish peroxidase following local immunization. After 5 d, peroxidase activity was found in vesicles located in macrophages and immature plasma cells. On day 7, peroxidase-antiperoxidase complexes were found in vesicles of the epithelial cells lining the secondary ducts and the acini, in the lumina of the ducts, and on the surface of lymphocytes located among these epithelial cells. Dendritic cells showing peroxidase activity on their surface were seen in the subepithelial lymphoid tissue and in the lymphoid follicles. On day 9, peroxidase activity was found as iccosomes on the surface of dendritic cells and lymphoblasts. These results indicate that immature plasma cells in the Harderian gland can take up antigen and may have a role in presenting it to T cells. Further, our results suggest that intraepithelial lymphocytes might be involved in antigen transportation from the epithelium to the subepithelial lymphoid tissue.