医学与人类健康呼吸系统常见疾病.ppt

* 07/16/96 * ## This is an acid fast stain of Mycobacterium tuberculosis (MTB). Note the red rods--hence the terminology for MTB in histologic sections or smears: acid fast bacilli. * 07/16/96 * ## Mycobacteria can also be stained with auramine and viewed with fluorescence microscopy, in which acid fast bacilli now appear as glowing yellow rods. This method is easier to use to screen for mycobacteria and is the method routinely used in sputum specimens sent to the laboratory. * 07/16/96 * ## * 07/16/96 * ## At high magnification, the granuloma demonstrates that the epithelioid macrophages are elongated with long, pale nuclei and pink cytoplasm. The macrophages organize into committees called giant cells. The typical giant cell for infectious granulomas is called a Langhans giant cell and has the nuclei lined up along one edge of the cell. The process of granulomatous inflammation takes place over months to years (did you ever hear of a committee action that was completed in a short time?) * 07/16/96 * ## Well-defined granulomas are seen here. They have rounded outlines. The one toward the center of the photograph contains several Langhans giant cells. Granulomas are composed of transformed macrophages called epithelioid cells along with lymphocytes, occasional PMNs, plasma cells, and fibroblasts. The localized, small appearance of these granulomas suggests that the immune response is fairly good. * 07/16/96 * ## On closer inspection, the granulomas have areas of caseous necrosis. This is very extensive granulomatous disease. This pattern of multiple caseating granulomas primarily in the upper lobes is most characteristic of secondary (reactivation) tuberculosis. However, fungal granulomas (histoplasmosis, cryptococcosis, coccidioidomycosis) can mimic this pattern as well. * 07/16/96 * ## The edge of a granuloma is shown here at high magnification. At the upper right is amorphous pink caseous material composed of the necrotic elements of the granuloma as well as