Functionally active Epstein-Barr virus-transformed follicular dendritic cell-like cell lines.

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Abstract
Follicular dendritic cells (FDC) are unique nonlymphoid cells found only in germinal centers. FDC can be distinguished from other accessory cells based on a characteristic set of cell surface markers. It is known that FDC are able to rescue germinal center B cells from apoptosis. To investigate the role of FDC in the process of selection and maturation of B cells during germinal center reactions, we tried to establish factor-independent immortalized FDC-like cell lines. Because freshly isolated FDC express the Epstein-Barr Virus (EBV) receptor CD21, we attempted EBV transformation on isolated FDC. After incubation of FDC-enriched cell populations with EBV, cell lines were obtained consisting of slowly duplicating very large cells. These cell lines have a fibroblast-like morphology but could be clearly distinguished from several human fibroblast cell lines by displaying a different phenotype including intercellular adhesion molecule 1, CD40, and CD75 expression. Detection of the EBV-encoded proteins latent membrane protein 1 and Epstein-Barr virus nuclear antigen 2 in our FDC-like cell lines implicated successful EBV transformation. FDC-like cells are able to bind nonautologous B cells and preserve the latter from apoptosis. The binding of B cells to FDC-like cells is dependent on adhesion via lymphocyte function-associated antigen 1/intercellular adhesion molecule 1 and closely resembles the pattern of emperipolesis as described by others. These data demonstrate that FDC can be successfully infected by EBV, and that the cell lines obtained share phenotypic and functional characteristics with freshly isolated FDC.