HUMAN FOLLICULAR DENDRITIC CELLS IN-VITRO AND FOLLICULAR DENDRITIC-CELL-LIKE CELLS

Human follicular dendritic cell (FDC)-like cells (FLC) have been utili zed for the in vitro analysis of germinal center reactions. However, t here is no consensus whether FLC represent FDC in vitro. The purpose o f the present study has therefore been to determine distinguishing fea tures of FDC and FLC in vitro. The expression of CD40, CD54, CD49d, cy tokine (gamma-IFN and IL-4)-dependent MHC-class II, and CD106 was obse rved to be specific for the determination of FDC in long-term culture. The cytokine-dependent emperipolesis of germinal center B cells was e stablished as another discriminating property for FDC in vitro. In 2 o ut of 72 long-term cultures of FDC, we encountered dividing cells amon g the non-dividing population of FDC. The dividing cells expressed acc essory molecules similar to those of FDC but showed emperipolesis only for the initial few days of their growth. FDC did not enhance the CD4 0-dependent proliferation of germinal center B cells; in contrast, FLC augumented it. Both types of cells produced a significant amount of c ytokine-dependent IL-6. Further studies are needed to determine whethe r FLC originate from FDC in vitro.