IDENTIFICATION OF AVIAN DENDRITIC CELLS IN THE SPLEEN USING A MONOCLONAL-ANTIBODY SPECIFIC FOR CHICKEN FOLLICULAR DENDRITIC CELLS

Background: In the chicken, circulating antigens enter the splenic whi te pulp via the Schweigger-Seidel sheaths (ellipsoids), where they are bound by cells, the ellipsoid associated cells (EAC), which are locat ed on the periphery of the ellipsoid. There is an increasing body of e vidence that these antigen-binding cells move through the PALS, to be finally located within the germinal centers, where these antigen-trans porting EAC function as follicular dendritic cells (FDC). The aim of t he current study was to further study the relationship between the EAC , the FDC, and the antigen-bearing EAC which migrate through the splen ic white pulp. Methods: In order to identify the splenic FDC and their presumed migrating EAC precursors in the chicken, we used a monoclona l antibody produced against chicken FDC and an antiserum anti-S-100 pr otein which identifies chicken dendritic cells in lymphoid organs. Res ults: Cells reacting with the 74.3 monoclonal antibody, which identifi es FDC, were found within the germinal center, around the penicillifor m capillary, in the periellipsoidal white pulp, and in the periarterio lar lymphatic sheaths (PALS). S-100(+) cells were found in these same locations. Conclusions: A comparison between the staining patterns obt ained with both antibodies strongly suggested that the intrasplenic di stribution of 74.3(+) cells was identical with that of FDC, EAC, and a ntigen-binding EAC migrating in the PALS. Therefore, the 74.3 monoclon al antibody identified not only FDC but also the splenic precursor cel ls of FDC, in accordance with the hypothesis of the migration of the E AC through the white pulp. S-100(+) cells were more numerous than 74.3 (+) cells, which is in accordance with the fact that S-100 protein ant ibody stains bath FDC and interdigitating dendritic cells (ID). This h as allowed us to suggest that 74.3(-) EAC may represent precursors of ID. The current findings reinforce previous investigations, which prov ided evidence supporting the migration of EAC through the PALS and fur ther supported the hypothesis which considers EAC precursors of FDC. ( C) 1997 Wiley-Liss, Inc.