IMMUNOHISTOCHEMICAL CHARACTERISTICS OF CHICKEN SPLEEN ELLIPSOIDS USING NEWLY ESTABLISHED MONOCLONAL-ANTIBODIES

Ellipsoids, the extra-vasculature sites surrounding penicilliary capil laries of the chicken spleen, play critical roles in the immune respon se and also in the clearance of pathogens or other particles. The mesh work of ellipsoids is formed by fibroblastic reticular cells. To chara cterize ellipsoidal reticular cells, a series of monoclonal antibodies against the chicken spleen have been developed. Of these antibodies, CSA-1 antibody reacts with fibroblastic reticular cells in ellipsoids and with endothelial cells. The reticular nature of positive cells in ellipsoids is indicated by immune-electron microscopy, and by double-s taining with anti-heat-shock protein 47 kDa (hsp47) antibody. The reac tion of CSA-1 with reticular cells is limited in ellipsoids; CSA-1 doe s not react with reticular cells in other lymphoid organs. These findi ngs indicate that ellipsoidal reticular cells share the antigen with e ndothelial cells. Ontogenic studies reveal that, on embryonic day 18, the development of ellipsoids is completed, penicilliary capillaries b ecome fenestrated, and CSA-1 expression in ellipsoids begins. These fi ndings suggest that CSA-1 is expressed on the cell surface of ellipsoi dal reticular cells once they are exposed to blood flow.