Role of interleukin-32 in the mechanism of chronic inflammation in IgG4-related disease and as a predictive biomarker for drug-free remission

Objectives: In immunoglobulin (Ig) G4-related disease (IgG4-RD), the mechanism of chronic inflammation and predictive factors for drug-free remission is still unclear. To examine the issues, we focused on tuberculosis, a chronic infection, and on the role of interleukin (IL)-32. Methods: We examined the positive rate of QuantiFERON TB-2G (QFT-2G) in 126 patients with IgG4-RD, and compared with the rate in the general population. Furthermore, specimens of submandibular glands from the maintenance treatment group and drug-free group of IgG4-RD and specimens of small salivary glands from primary Sjogren's syndrome (SS) were stained with anti-IL-32 antibody and anti-protease-activated receptor 2 antibody, and the number of positive cells was compared between these groups. Results: The positive rate of QFT-2G was 19.8% in IgG4-RD patients, which is higher than in the general population. The expression of IL-32 and PAR2 in the submandibular glands of the maintenance treatment group of IgG4-RD was significantly greater than that of the drug-free remission group and SS patients. Conclusions: This study indicates the possibility that IL-32 is associated with chronic inflammation and that it can be a predictive factor for drug-free remission in IgG4-RD.