Conclusions
Patients with sarcoidosis have mycobacterial antigen-specific Th-17 cells peripherally and in sites of active sarcoidosis involvement. Despite the Th1 immunophenotype of sarcoidosis immunology, the Th-17 cells have reduced IFN-γ expression, compared to healthy controls. This reduction in immunity may contribute to sarcoidosis pathogenesis.
Methods
Flow cytometry was used to determine the numbers of Th-17 cells present in the peripheral blood and BALF of patients with sarcoidosis, the percentage of Th-17 cells that were specific to the mycobacterial virulence factor ESAT-6, and as well as to assess IFN-γ expression in Th-17 cells following polyclonal stimulation.
Results
Patients with sarcoidosis had greater numbers of Th-17 cells in the peripheral blood and BALF than controls and produced significantly more extracellular IL-17A (p = 0.03 and p = 0.02, respectively). ESAT-6 specific Th-17 cells were present in both peripheral blood and BALF of sarcoidosis patients (p < 0.001 and p = 0.03, respectively). After polyclonal stimulation, Th-17 cells from sarcoidosis patients produced less IFN-γ than healthy controls. Conclusions: Patients with sarcoidosis have mycobacterial antigen-specific Th-17 cells peripherally and in sites of active sarcoidosis involvement. Despite the Th1 immunophenotype of sarcoidosis immunology, the Th-17 cells have reduced IFN-γ expression, compared to healthy controls. This reduction in immunity may contribute to sarcoidosis pathogenesis.