Ultrastructural correlation between follicular dendritic cells and the frequency of virus-like particles during the lymph nodes reaction of SIV/HIV 2 infected cynomolgus monkeys.

: Lymph nodes from 18 SIV/HIV2 infected monkeys developing a severe AIDS-like disease were studied by electron microscopy. The lesions were correlated with the histopathologic staining and the anti-SIVp28 immunostaining. The investigation of follicular dendritic cells (FDC) and associated retroviral particles was focused on the light zones of germinal centres during the follicular hyperplasia, fragmentation atrophy and depletion. FDCs were mostly developed in the first two stages, while the highest amount of retroviruses was found in the two middle stages. During the last stage of follicular depletion FDCs were still present but deprived of dendrites and no viral particles were seen around. Associated lesions were small haemorrhages, binucleated FDCs, viral phagocytosis by macrophages and reticular paracrystalline inclusions.