A sarcoidosis patient developed non caseating granulomas. Which type of hypersensitivity is responsible for developing granulomatous inflammation in this patient?
Delayed-type hypersensitivity or or type IV hypersensitivity is a T-cell mediated or inflammatory response in which the stimulation of antigen-specific effector T cells leads to macrophage activation and localized inflammation and edema within tissues. Three variants of type IV hypersensitivity reaction are recognized, contact, tuberculin type and granulomatous. Contact hypersensitivity and tuberculin-type hypersensitivity both occur within 72 hours of antigen challenge. Granulomatous hypersensitivity reactions develop over a period of 21-28 days - the granulomas are formed by the aggregation of macrophages and lymphocytes and may persist for weeks. This is the most impoant type of hypersensitivity response for producing clinical consequences. Examples of chronic diseases which manifest type IV granulomatous hypersensitivity are leprosy, tuberculosis, schistosomiasis, sarcoidosis, Crohn's disease. Ref: Immunology By David K. Male, 2006, Page 477, 486 ; Immunology by David K. Male, Jonathan Brostoff, Ivan Maurice Roitt, David B. Roth, Page 477-478
Type I
Type II
Type III
Type IV