Serum levels of interleukin-32 and interleukin-6 in granulomatosis with polyangiitis and microscopic polyangiitis: association with clinical and biochemical findings.

BACKGROUND

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis is an autoimmune disorder of unknown etiology with dysregulated cytokines levels.

OBJECTIVES

The main aim of this study was to assess the clinical correlation between antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis, granulomatosis with polyangiitis (GPA) serum levels of the microscopic polyangiitis (MPA), serum levels of the proinflammatory cytokines, interleukin (IL)-32 and interleukin-6.

METHODS

Study included 71 patients, 47 with GPA and 24 with MPA. Serum IL-32 and IL-6 concentrations were analyzed in all patients, and compared with levels observed in 10 controls. IL-32 and IL-6 were evaluated using DuoSet and Quantikine HS ELISA, respectively. IL-32 and IL-6 concentrations were correlated with disease-related clinical and laboratory findings.

RESULTS

IL-32 and IL-6 levels were significantly higher in GPA and MPA than in controls, especially IL-32 levels in GPA were elevated. IL-32 concentrations correlated positively with anti-proteinase 3 - ANCA (PR3-ANCA) levels in GPA (P < 0.0001), and with anti-myeloperoxidase ANCA (MPO-ANCA) in MPA (P = 0.049). IL-32 levels correlated positively with disease activity in GPA and MPA (P < 0.0001). GPA patients with pulmonary, cutaneous, and musculoskeletal involvement presented the highest IL-6 serum levels. Cutaneous manifestations correlated positively with IL-6 levels in MPA patients (P = 0.05). ANCA-positive patients with GPA expressed significantly high IL-6 levels (P = 0.036). No significant difference in IL-32 values was observed between ANCA-positive and ANCA-negative patients.

CONCLUSIONS

Patients with GPA and MPA present higher serum IL-32 and IL-6 levels than controls. IL-32 levels correlate positively with disease activity.