HBMECs express the IL-6 receptor and HIV-1 exposure increases receptor expression. Exposure of HBMECs to HIV-1 for 30 minutes significantly increased the expression of both alpha (IL6-R-α; A,B) and beta (Gp130; A,C) subunits of the IL-6 receptor, and altered endothelial cell phenotype (A). HIV-1–induced up-regulation of IL6-R-α expression was transient and decreased after 30 minutes (A,B), while HIV-induced increase in Gp130 expression was sustained for up to 2 hours (C). Control represent untreated HBMECs; NI-control consisted of HBMECs exposed for 1 hour to conditioned media from noninfected macrophages. Original magnification of images in panel A: ×200.