Anti-S-100 antibody recognizes ellipsoid-associated cells and other dendritic cells in the chicken spleen.

The chicken spleen was studied immunohistochemically with anti-S-100 protein polyclonal antibody. S-100-positive cells accumulated around the penicilliform capillaries during the first 3 weeks of life. After 2 weeks posthatch the S-100-positive cells appeared in the red pulp, periarterial lymphatic sheath, and subsequently in the germinal center. Their ontogenetic development and intrasplenic distribution strongly suggested that the S-100-positive cells were identical with ellipsoid-associated cells. The S-100-negative cells of the periellipsoidal white pulp gradually transformed to S-100-positive, functionally active cells on the surface of the ellipsoid. The immunohistological findings support the hypothesis that the interdigitating dendritic cells and follicular dendritic cells were not of monocytic origin but belong to a splenic resident, endocytic cell line located on the surface of the ellipsoid.