Antimycobacterial immuneresponses in patients with pulmonary sarcoidosis

Sarcoidosis is a multisystem granulomatous disease of unknown origin. Pathogenetic involvement of Mycobacterium tuberculosis has frequently been discussed, however, studies still remain contradictory. We examined the interferon (IFN)-γ production by enzyme-linked-immunospot in response to purified protein derivate (PPD) and mycobacterial specific antigens early-secretory-target (ESAT)-6 and culture-filtrate-protein (CFP)-10 by peripheral blood mononuclear cells (PBMC) and bronchoalveolar-lavage mononuclear cells (BALMC) of patients with pulmonary sarcoidosis, smear-negative tuberculosis and controls. Release of IFN-γ in response to ex vivo contact with PPD, ESAT-6 or CFP-10 by BALMC and PBMC were comparable among patients with sarcoidosis and controls (PBMC p=0.1630; BALMC p=0.2199) and were less freuqently observed in both groups compared to patients with tuberculosis (BALMC p<0,0131; PBMC p<0.0001). Within PBMC the immunephenotype of sarcoidosis-patients differed from patients with tuberculosis, as well as from controls, while within BALMC it resembled the one of patients with tuberculosis. In contrast to patients with tuberculosis, the frequency of mycobacteria-specific local and systemic immunresponses is not elevated in patients with sarcoidosis when compared to controls. The immunephenotype represents the local resemblance of the granulomatous reaction underlying tuberculosis and sarcoidosis, while showing systemical difference. These observations do not support a role of a mycobacterial infection in the pathogenesis of sarcoidosis.