The following host response can be seen in acute infection,except
Ref Robbins 9/e p97 Granulomatous Inflammation Granulomatous inflammation is a distinctive pattern of chronic inflammation characterized by aggregates of acti- vated macrophages with scattered lymphocytes. Granulo- mas are characteristic of ceain specific pathologic states; consequently, recognition of the granulomatous pattern is impoant because of the limited number of conditions (some life-threatening) that cause it (Table 2-8). Granulo- mas can form under three settings: * With persistent T-cell responses to ceain microbes (such as Mycobacterium tuberculosis, T. pallidum, or fungi), in which T cell-derived cytokines are responsible for chronic macrophage activation. Tuberculosis is the proto- type of a granulomatous disease caused by infection and should always be excluded as the cause when granulomas are identified. * Granulomas may also develop in some immune- mediated inflammatory diseases, notably Crohn disease, which is one type of inflammatory bowel disease and an impoant cause of granulomatous inflammation in the United States. * They are also seen in a disease of unknown etiology called sarcoidosis, and they develop in response to rela- tively ine foreign bodies (e.g., suture or splinter), forming so-called foreign body granulomas. The formation of a granuloma effectively "walls off" the offending agent and is therefore a useful defense Disease Cause Tissue Reaction Tuberculosis Mycobacterium tuberculosis Caseating granuloma (tubercle): focus of activated macrophages (epithelioid cells), rimmed by fibroblasts, lymphocytes, histiocytes, occasional Langhans giant cells; central necrosis with amorphous granular debris; acid-fast bacilli Leprosy Mycobacterium leprae Acid-fast bacilli in macrophages; noncaseating granulomas Syphilis Treponema pallidum Gumma: microscopic to grossly visible lesion, enclosing wall of histiocytes; plasma cell infiltrate; central cells are necrotic without loss of cellular outline Cat-scratch disease Gram-negative bacillus Rounded or stellate granuloma containing central granular debris and neutrophils; giant cells uncommon Sarcoidosis Unknown etiology Noncaseating granulomas with abundant activated macrophages Crohn disease Immune reaction against intestinal bacteria, self antigens Occasional noncaseating granulomas in the wall of the intestine, with dense chronic inflammatory infiltrate Table 2-8 Examples of Diseases with Granulomatous Inflammation MORPHOLOGY In the usual H&E preparations (Fig. 2-23), some of the activated macrophages in granulomas have pink, granular cytoplasm with indistinct cell boundaries; these are called epithelioid cells because of their resemblance to epithelia. Typically, the aggregates of epithelioid macrophages are sur- rounded by a collar of lymphocytes. Older granulomas may have a rim of fibroblasts and connective tissue. Frequently, but not invariably, multinucleate giant cells 40 to 50 mm in diameter are found in granulomas. Such cells consist of a large mass of cytoplasm and many nuclei, and they derive from the fusion of multiple activated macrophages. In granulomas
Exudation
Vasodilation
Margination
Granuloma formation
General anatomy