Demonstration of isolated follicular dendritic cells in lymphatic vessels around human immunodeficiency virus-infected lymph nodes.

Follicle lysis (FL) is a peculiar disruptive change of follicular dendritic cells (FDCs) commonly observed in the germinal centres of individuals with HIV infection. To clarify the fate of FDCs during FL, 30 HIV-infected lymph nodes were studied, mostly in the persistent generalized lymphadenopathy phase. FDCs were immunostained on paraffin sections with 1F8, a FDC-specific monoclonal antibody. In advanced FL, the FDC network was shown to be divided into cell clusters of various sizes. In the final phase of FL, these were fragmented into much smaller cell clusters and dispersed in the parafollicular area. Some of these small clusters were found in the lymphatic sinuses (6/30), and unexpectedly, even in extranodal lymphatic vessels (2/30, one being apparently located in efferent vessels). No efflux of these small FDC clusters into extranodal lymphatics was observed in 15 HIV-negative control lymph nodes. These FDC clusters located in the lymphatics may work as transporters of HIV to other lymph nodes downstream, as FDCs carry the greatest HIV load.