Type I interferon and T helper 17 cells co-exist and co-regulate disease pathogenesis in lupus patients

Aim: T-helper 17 cells (Th17) and type I interferon (IFN-I) play a critical role in the pathogenesis of systemic lupus erythematosus (SLE). Previous studies have suggested that IFN-I suppresses Th17 development under autoimmune settings. Therefore, the main objective of this study was to define the association between IFN-I and Th17 pathways in SLE. Methods: Peripheral blood samples and disease activity measures were collected from 31 patients fulfilling the American College of Rheumatology revised criteria for SLE. Serum was evaluated for IFN-α bioactivity and interleukin (IL)-6 levels by cell-based bioluminescence assay and enzyme-linked immunosorbent assay, respectively. The frequency of Th17 cells in peripheral blood was determined by intracellular cytokine staining for IL-17. Results: IFN-α bioactivity in the serum of lupus subjects (mean ± SD: 6.510 ± 3.686) was significantly higher (P = 0.001) compared to healthy controls (2.9 ± 1.061). Additionally, 58.1% and 41.9% of SLE subjects displayed high and low IFN-α bioactivity, respectively. We observed a significant increase (P = 0.04) in the percentage of Th17 cells in lupus subjects with high IFN-α bioactivity (1.9 ± 1.0) compared to lupus subjects with low IFN-α bioactivity (1.2 ± 0.9). Lupus subjects with high IFN-α bioactivity and Th17 cells had significantly higher disease activity (P = 0.04) and serum IL-6 levels (P = 0.01) compared to patients with low IFN-α activity and low Th17 cells. Conclusion: Type I interferon and Th17 pathways co-exist and co-regulate the pathogenic processes in SLE. Additionally, these studies clearly identify IL-6 as a common link between IFN-I and Th17 pathways in SLE pathogenesis.