Epithelial damage and repair in ex vivo tonsil organ culture and HIV infection of tonsil cells. Small randomly cut pieces of tonsil tissue reacquired an epithelial cell coating during organ culture. Thin sections were incubated with primary antibodies and species-specific conjugated secondary antibodies as indicated. a: CCR5; b: CXCR4; c: CCR5 (red) plus CXCR4 (green), cells that are positive for both fluorescent markers appear yellow. Original magnification a, b, c: ×200. Tonsil cell suspensions were infected with HIV 96–480 patient isolate virus stock, then cells were spotted onto glass slides for immunocytochemical detection of HIV p24 gag: d: day 0, prior to infection; e: day 5; and f: day 10 after infection; g: enlargement from f. HIV infected cells are stained brown; cell nuclei were identified with a hematoxylin counterstain. Original magnification d, e, f: ×100; g: ×400.