SDF-1 and CXCR-4 expression in cutaneous KS lesions. (A) Parallel sections from a formalin-fixed biopsy of an AIDS-KS skin lesion stained with hematoxylin and eosin (H&E) for SDF-1 and double stained for KSHV-LANA/SDF-1. H&E staining reveals normal epidermis overlaying a spindle cell proliferation consistent with cutaneous involvement with KS. SDF-1 immunostaining reveals intensely positive spindle cells within the KS lesion (dark arrow); endothelial cells lining skin capillaries (open arrow) and dendritic cells (arrowhead) in the skin overlaying the KS lesion are also SDF-1 positive. Original magnifications, × 40 (i,ii) and × 60 (iv,v). (iii,vi) Double staining for KSHV-LANA (red) and SDF-1 (brown) reveals that spindle cells confined to the KS lesion are positive for both LANA and SDF-1 (original magnification, × 100). (B) Parallel sections from a frozen biopsy of an AIDS-KS skin lesion stained with antihuman CXCR-4 monoclonal antibody or control monoclonal antibody. CXCR-4–specific immunostaining is confined to scattered cells within superficial dermis. Original magnifications, × 20 (left and middle panels) and × 100 (right panel). (C) Western blot analysis of SDF-1 and CXCR-4 expression in tissues and cell cultures detected by specific antibodies against SDF-1 and CXCR-4. Cell lysates were obtained from BL41 cells (lane 1), HUVECs (lane 2), KS tissue from 2 patients (lanes 3-4), and normal skin (lane 5). Protein loading was evaluated by reprobing the membrane with anti-actin antibodies.