Antigenic Phenotype of Rodent Follicular Dendritic Cells in Vitro and in Situ

Abstract

Follicular dendritic cells (FDCs) were first described at the transmission electron microscopic level in the lymph node by Nossal et al. (1968) and in the spleen by Szaka1 and Hanna (1968). Until recently, the study of FDCs was limited to in situ investigations due to the lack of adequate isolation and enrichment techniques. In 1982, Schnizlein et al. developed a procedure in our laboratory which produced a single cell suspension specifically enriched for FDCs from lymph nodes of mice. This procedure provided an opportunity to establish diagnostic morphological features of intact FDCs in vitro, using Nomarski optics, scanning EM (SEM) and transmission EM (TEM). The SEM of isolated FDCs revealed cells with a “sunburst-like” appearance due to numerous long thin dendrites emanating from a spherical or ovoid cell body. Nomarski optics and TEM confirmed the presence of immune complexes on the processes of FDCs by using the histochemically detectable antigen (Ag), horseradish peroxidase (HRP), and revealed features consistent with those observed in lymphoid sections. The cytological evaluation of FDCs in vitro provided functionally supported morphological criteria by which these cells could be distinguished from leukocytes and other dendritic cells (Szakal, Gieringer, Kosco and Tew, 1984).