An antiserum against Eimeria tenella sporozoites was used to localize and isolate Ag-binding cells in intestinal cecal tonsils of parasite-infected chickens. Based on their tissue localization, ultrastructural features, and expression of surface markers, two subpopulations of cells were isolated, CD45(+) interdigitating dendritic cells (IDCs) and CD45(-) follicular dendritic cells (FDCs). IDCs expressed MHC class I, MHC class II, and selectin, induced the proliferation of allogeneic naïve CD4(+) T cells, and increased the secretion of IFN-gamma by autologous T cells. FDCs expressed surface IgG, IgM, ICAM-1, and VCAM-1, stimulated the proliferation of LPS-treated allogeneic B cells, and augmented the secretion of IgG by LPS-treated autologous B cells. Final cell yields were 6 x 10(5) to 8 x 10(5) cells per chicken with >95% purity. In summary, this combination of methods using Abs against E. tenella and CD45 made it possible for the first time to obtain a highly enriched IDCs and FDCs which are functionally active in chickens. This novel method will enable the detailed biochemical and immunological characterizations of avian dendritic cells and facilitate the investigation of their role in initiating immune response in normal and disease states.