The etiologic role of infectious antigens in sarcoidosis pathogenesis

Celada, Lindsay J.; Hawkins, Charlene; Drake, Wonder P.

Sarcoidosis is a granulomatous disease of unknown etiology, characterized by a Th1 immunophenotype, most commonly involving the lung, skin, lymph node and eyes. Molecular and immunologic studies continue to strengthen the association of sarcoidosis with infectious antigens, particularly those derived from Propionibacterium and Mycobacterium species. Independent studies report the presence of microbial nucleic acids and proteins within sarcoidosis specimens. Complementary immunologic studies also support the role of infectious agents in sarcoidosis pathogenesis. Th-1 immune responses directed against mycobacterial virulence factors have been detected within sarcoidosis diagnostic bronchoalveolar lavage (BAL). Th1 and Th17 immune responses against propionibacteria have also been reported. More recently, case reports and clinical trials from Japanese, European and American investigators have emerged regarding the efficacy of antimicrobials against Propionibacterium and Mycobacterium species on pulmonary and cutaneous sarcoidosis. While these clinical investigations are not conclusive, they support increasing efforts to identify novel therapeutics, such as antimicrobials, that will impact the observed increase in sarcoidosis morbidity and mortality.