Reappraisal of histogenesis in the bursal lymphoid follicle of the chicken

Abstract

The development of the bursal follicle and the appearance of the follicle-associated epithelial (FAE) cell and the reticuloepithelial (REp) cell were studied. The stages of development of the bursal follicle were observed by light and electron microscopy; an anticytokeratin monoclonal antibody was also used. At the beginning of follicle development, a mesenchymal cell cluster is observed in the tunica propria; the cluster becomes wedged in a niche of the surface epithelium, and gradually it is completely surrounded by the epithelium itself, which closes under the clump of mesenchymal cells. The epithelial cells lying upon the mesenchymal clump become necrotic, and a number of mesenchymal cells bulge out, forming the FAE cells. The epithelial cells that have closed under the mesenchymal nodule become stratified and form the REp cells; they become star-shaped because the medullary-lymphoid cells grow between them. Finally, the cortex is formed, possibly as a result of the migration of medullary cells before they peripheralize. It is concluded that FAE cells are not specialized epithelial cells, as they do not react to an anticytokeratin monoclonal antibody; on the contrary, they are formed by mesenchymal stemcells that bulge into the lumen and change their character after moving into the epithelium. The REp cells appear in the follicular primordium shortly after the bursal follicle begins to develop; the pronounced reactivity of the REp cells to an anticytokeratin monoclonal antibody supports the hypothesis of their epithelial origin.

Localization of Estrogen Receptor in the Central Lymphoid Organs of Chickens during the Late Stage of Embryogenesis

“…22,23) It is thought to play an important role in allowing the antigen to enter into the lymphoid follicle and excluding foreign substances from the lymphoid follicle, but the detailed of the function of FAE at the molecular level are largely unknown. 13,14) However, it has been reported that the entry of foreign substances into the BF is necessary to the acquisition of antibody diversity.…”

Identification of cells secreting a thymostimulin-like substance and examination of some histoenzymatic pathways in aging avian primary lymphatic organs: II. Bursa of Fabricius

“…It has been reported that the FAE cells are epithelial cells (Schaffner et al, 1974a;Schaffner et al, 1974b;Davenport and Allen, 1995;Paramithiotis and Ratcliffe, 1996), which are positive (Viamontes et al, 1989), or weakly positive (Olah and Glick, 1992) to anti-cytokeratin antibodies. Other authors reported that they are mesenchymal cells (Dolfi et al, 1981;Lupetti et al, 1983Lupetti et al, , 1986Lupetti et al, 1990), that are negative to anti-cytokeratin . Olah et al (2001) and Nagy et al (2001) found that the monoclonal antibodies to GIIF3 and NIC2, which are able to recognize mesenchymal elements, were expressed by FAE cells and cortico-medullary cells.…”

“…The reticular-epithelial cells detected during embryonic development (Jolly, 1914;Ackerman and Knouff, 1959;Ackerman, 1962;Lupetti et al, 1990) or in adult life (Frazier, 1974;Glick, 1983;Houssaint et al, 1986;Eerola et al, 1987;Dolfi et al, 1990;Olah and Glick, 1992) have been described by ultrastructural studies (Frazier, 1974) and classified as pale, dark and intermediate cells. These cells had cytoplasmic processes which were often connected to the adjacent epithelial cells forming a supporting network for the lymphocytes.…”

“…Other cells in the medulla were free. They could be stained by anti-cytokeratin sera (Viamontes et al, 1989;Dolfi et al, 1990;Lupetti et al, 1990;Olah and Glick, 1992) and detected by specific monoclonal antibodies (Houssaint et al, 1986;Houssaint, 1987;Boyd et al, 1990).…”

The Structure Of Bursa Of Fabricius In The Long-Legged Buzzard (Buteo Rufinus): Histological And Histochemical Study

“…The mucosa contains several plications and a large number of polyhedral lymphoid follicles [8], composed of cortex, medulla and corticomedullary border [9,10]. The surface comprised two kinds of epithelium: follicle associated epithelium (FAE) covering the apex of each lymphoid follicle and the interfollicular epithelium (IFE) covering the space between the lymphoid follicles [3,11].…”