Objective: We compared levels of Th1/Th2/Th17 cytokines and T-regulatory cells in active and remitting granulomatosis with polyangiitis (GPA).
Methodology: Twenty-one cases of GPA in active state as well as in remitting state and 20 healthy controls (HC) were enrolled in the study. Cytokines were detected in culture supernatants of PBMCs after stimulation with proteinase-3 (PR3) and phytohemagglutinin antigen (PHA). Serum IL-17 cytokine was studied by ELISA. T-regulatory cells (Tregs) were analyzed by flow cytometry. Gene expression of FOXP3 and ROR-γt was compared by Real Time PCR.
Results: We observed significantly increased level of IL-17 in serum as well in culture supernatants of PBMCs after PR3 stimulation along with ROR-γt gene expression in active disease state of GPA as compared to HC. Importantly, remitting state showed low levels of serum IL-17 with decreased ROR-γt gene expression and increased FOXP3 expression. Using PR3 as an immunostimulant, we could demonstrate the generation of IL-17 and TNF-α secreting effector memory cells during remission. Reduced FOXP3 expression with reduced IL-10 levels in active disease indicated the reduced function of Tregs in active disease.
Conclusion: We observed Th17 dominant environment in peripheral blood of patients in active state of disease, with "hyporesponsiveness", in, in vitro stimulated PBMC-in their ability to secrete TNF-α and IL-6. Treg numbers were unaltered but function was compromised. Targeting PR3 specific effector memory cells, to prevent relapse, and instituting anti IL-17 therapy, or modulating Tregs could be newer forms of therapy for this serious autoimmune disease.
Keywords: Cytokines; GPA; Immunopathology; T-cells; Tregs.
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