FOLLICULAR DENDRITIC CELLS (FDC) IN RETROVIRAL INFECTION - HOST PATHOGEN PERSPECTIVES/

Follicular dendritic cells (FDC) are found in the follicles of virtual ly all secondary lymphoid tissues. In health, these cells trap and ret ain antigens (Ag) in the form of immune complexes and preserve them fo r months in their native conformation. FDC thus serve as a long-term r epository of extracellular Ag important for induction and maintenance of memory responses. In retroviral infection, FDC trap and retain larg e numbers of retroviral particles with profound effects on FDC. FDC-tr apped retrovirus induces follicular hyperplasia, and conventional Ag t rapped prior to infection are lost and new Ag cannot be trapped. Conco mitantly, antibody-forming cells (AFC) specific for Ag lost from FDC d ecrease followed by loss of specific serum antibody (Ab). Eventually, FDC die and follicular lysis occurs. From the pathogen perspective, bi nding to FDC is remarkably beneficial, bringing together virus and act ivated target cells that are highly susceptible to infection. Furtherm ore, FDC permit HIV to infect surrounding cells even in the presence o f a vast excess of neutralizing Ab. Preliminary data suggest that FDC maintain virus infectivity - even when the virus cannot replicate. Thu s retrovirus infection monopolizes FDC networks, thereby transforming the FDC Ag repository into a highly infectious retroviral reservoir.