Bursal secretory cells: An electron microscope study

In addition to lymphocytes, macrophages, and epithelial cells, the bursa medullapossesses a cellwe have named the secretory cell. The secretory cell, which makes up approximately 0.5% of the bursal cellpopulation, exhibits an eccentric nucleus with a chromatin pattern similar to that of a small lymphocyte and an elongated cytoplasm with one or more cellprocesses. The electron-dense cytoplasmic granules of the immature secretory cellare localized around the cytocentrum, while in the mature secretory cellthese granules are situated beneath the cellmembrane of one process. The granular location endows a polarized appearance to the secretory cell. The surface of the membrane is covered with a finely spotted flocculated substance, which may originate from a granular discharge. The round, ovoid, or irregular-shaped granules reveal a homogeneous or distinctive internal pattern. The cortico-medullary border may be the germinal layer of the bursal medulla. The bursal secretory cellis a modified dendritic cellwith possible endocrine functions that may be important in B- cellinduction.