Follicular dendritic cells (FDC) represent a novel cell type found in the B-cell regions of all secondary lymphoid tissues. The name follicular dendritic cell and the abbreviation FDC have been recommended by a committee on nomenclature (Tew et al. 1982) but a number of names have been used in the literature including: dendritic reticulum cells (DRC), antigen retaining reticular cells, follicular ii6-mune complex retaining cells, follicular antigen-binding dendritic cells, follicular reticular cells, follicular dendritic reticulum cells, Nossal's follicular dendritic reticulum cells and dendritic macrophages (Tew et al. 1982). However, in recent years the name follicular dendritic cell has been generally adopted. Two features differentiate FDC from other accessory cells and are considered diagnostic or cardinal: 1) these dendritic cells are restricted to lymphoid follicles and 2) they trap and retain immune complexes on their surfaces for long periods of time (Tew et al. 1982). It was these two features that caught the attention of Szakal & Hanna as well as Nossal et al. in 1968, when both groups identified FDC as the cells responsible for retaining antigen.

Important features which help to further characterize FDC are listed in Table I. This is a selected series of markers chosen to emphasize relationships between FDC and other leukocytes as well as discrepancies in the literature. References at the bottom of Table I contain some further phenotypic information. In addition to the cardinal features relating to anatomical location and retention of surface immune complexes, a number of other features appear to be highly consistent among FDC in different species. These include: lack of phagocytie activity, highly convoluted dendritic processes, an irregularly shaped euchromatic nucleus, presence of receptors for complement fragments, and the expression of the adhesion molecule ICAM-1. As indicated in Table I, there are features where the