Which of the following statement is not true about mycobacterium tuberculosis infection
Ref Robbins 8/e p368; 9/e p371 Macrophage are primary cells infected by M tb 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 mechanism. However, granuloma formation does not always lead to eradication of the causal agent, which is frequently resistant to killing or degradation, and granulo- matous inflammation with subsequent fibrosis may even be the major cause of organ dysfunction in some diseases, such as tuberculosis.
M.TB leads to development of delayed hypersensitivity
Lymphocytes are the primary cells infection by M.TB
Positive tuberculin test signifies cell mediated hypersensitivity
Tuberculin test not differentiated between infection and disease
General anatomy