New monoclonal antibodies directed against mouse follicular dendritic cells

The follicular dendritic cells (FDC) in B-lymphoid follicles are unique reticular cells that retain immune complexes on their surfaces. We developed new monoclonal antibodies (MAb), SKY01, 28, 41, and 49, against mouse FDC without useful cell markers. Immunohistochemical study of spleen and lymph node tissues from Balb/c, C3H, and C57BL/6 mice revealed that SKY01 and 49 were highly specific for FDC, whereas SKY28 and 41 reacted with other stromal components as well as FDC. On immunoelectron microscopy (IEM), reaction products for all MAb were localized on the surfaces of FDC. In ontogenetic study of Balb/c spleen, FDC precursors were not immunodetected with any of the MAb at 1 week after birth. The FDC that first appeared as immune complex-retaining cells at 2 weeks were a subpopulation of SKY01-, 49-, 28+, and 41+ reticular cells. At 3 weeks, FDC were positive for all MAb, like adult spleen. These results indicate that our MAb recognize differentiation antigens of FDC. Comparative immunohistochemical studies of spleen from athymic nude and severe combined immunodeficiency mice suggested that B-cells may be required for the differentiation of FDC. Consequently, these MAb are considered useful tools for research on FDC.