Kaposi's sarcoma in AIDS: basement membrane and endothelial cell markers in late‐stage lesions

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Abstract
Early‐stage lesions of Kaposi's sarcoma (KS) are composed of single‐layered, highly flattened cells lining collagen bundles, whereas late‐stage lesions contain densely packed, spindle‐shaped cells. We examined the progression of KS lesions in oral mucosa and lymph nodes from patients with AIDS, using antibodies specific for blood vascular endothelial cells (Factor VHI‐related antigen) and their basement membrane (Type IV collagen and laminin). In addition, the plant lectin Ulex europaeus, which selectively stains blood vessels, was also used. In early‐stage KS lesions, fibronectin, laminin and Type IV collagen were co‐distributed at the interface between KS cells and collagen bundles; Factor VHI‐related antigen and Ulex europaeus lectin staining was present in vascular channels and in the KS cells. However, in late‐stage lesions, few if any KS cells stained with antibody to Factor VHI‐associated antigen, although endothelial cells lining blood vessels were positive. Strong staining for laminin and Type IV collagen was present in a pericellular pattern throughout the nodular late‐stage lesions. Since lymphatic capillary endothelium does not produce basement‐membrane‐specific macromolecules, these results support the conclusion that KS cells are related to blood vascular endothelium but eventually lose certain endothelium‐specific markers as the cells are transformed into the spindle‐shaped cell type.