Search

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.

The aim of the present study was to isolate chicken follicular dendritic cells (FDC). A combination of methods involving panning, iodixanol density gradient centrifugation, and magnetic cell separation technology made it possible to obtain functional FDC from the cecal tonsils from chickens, which had been infected with Eimeria tenella. CD45- dendritic cells were selected using the specific monoclonal antibody against chicken CD45, which is a marker for chicken leukocytes, but is not expressed on chicken FDC. Isolated FDC were characterized morphologically, phenotypically and functionally. The phenotype of the selected cells was consistent with FDC in that they expressed IgG, IgM, complement factors C3 and B, ICAM-1, and VCAM-1, but lacked cell surface markers characteristic of macrophages, T-, and B cells. Transmission electron microscopy confirmed their characteristic dendritic morphology. In addition, the identity of the FDC was further confirmed by their ability to trap chicken immune complexes (ICs) on their surface, whereas they did not trap naive antigen (ovalbumin) or ICs generated with mammalian immunoglobulins. Co-culturing allogeneic or autologous isolated FDC with B cells resulted in enhanced B cell proliferation and immunoglobulin production. The lack of MHC restriction, a functional characteristic feature of FDC, further reinforces the identity of the isolated cells as chicken FDC.