Production of FBA-tb by M. tuberculosis bacilli in vivo. A and B, lung granulomas from M. tuberculosis Erdman-infected IFN-γ-KO mice (×40). A, fluorescent auramine-rhodamine stain of M. tuberculosis bacilli. B, FBA-tb (red) was detected by immunohistochemistry using polyclonal anti-FBA-tb antibodies and tyramide amplification signal. C–E, lung granulomas from M. tuberculosis H37Rv-infected guinea pigs (×20). C, fluorescent auramine-rhodamine stain of M. tuberculosis bacilli. Fluorescent (D) and confocal (E) micrographs of co-localizing FBA-tb (red) and GroES (green) proteins that were detected by immunohistochemistry within the necrotic core of guinea pig lung tissues are shown. White arrows denote co-localization.