MORPHOLOGICAL-CHANGES IN LYMPH-NODES AND EXPRESSION OF VCAM1 AND CYTOKINES AT THE LATE STAGES OF SIV-INDUCED DISEASE IN RHESUS-MONKEYS

Four patterns of structural alterations were found in lymph nodes (LNs ) from rhesus monkeys 17 to 34 months after infection with simian immu nodeficiency virus (SIV-mac251). SIV p27gag antigen and viral particle s were localized either between the processes of follicular dendritic cells (FDCs) or in the cytoplasm of macrophages. In hyperplastic folli cles, enlarged germinal centres contained numerous Ki67(+) proliferati ng centroblasts which were rather rare in light zones occupied by the CD23(+) FDC network. Involuted follicles contained a small number of K i67(+) centroblasts and the CD23 labelling was limited to a very small apical zone. A correlation was found between the morphological charac teristics of the follicles (hyperplasia-involution) and the level of e xpression of the vascular cell adhesion molecule 1 (VCAM1) on FDCs. A gradient in VCAM1 intensity with no expression in the subcapsular-inte rmediary sinuses, low membrane labelling in the mantle and strong expr ession in the FDC network was observed. IL1 alpha(+) and IL6(+) (inter leukin) cells (lymphocytes and macrophages) were detected in the mantl e, the interfollicular area and the medulla of LNs. Expression of the tumour necrosis factor alpha and ultrastructural markers of interferon alpha production were found in a few FDC and macrophages. Our finding s indicate a close relationship between the morphofunctional propertie s of FDC and the LN structure in SIV infection.