Primary Sjögren syndrome (pSS) is a systemic autoimmune rheumatic disease that particularly affects exocrine glands. Dry eye is one of the most important features of this syndrome, and a recent study reported reduced deoxyribonuclease I (DNase I) activity in the tear of patients with dry eye. We therefore postulated that patients with pSS might have antibodies targeting DNAse I.
We have evaluated in a cross-sectional study 85 patients with pSS (2002 American-European Consensus Group Criteria), 50 rheumatoid arthritis (RA) patients (1987 American College of Rheumatology Criteria) without sicca symptoms, and 88 healthy volunteers. IgG anti-DNase I was detected by enzyme-linked immunosorbent assay using as antigen bovine pancreas enzyme and confirmed by immunoblotting.
Age and sex were alike in the 3 groups (p > 0.05). Anti-DNase I was detected in 43.5% of the pSS patients. In contrast, this reactivity was absent in all RA patients (p = 0.0001). Additional comparison of pSS patients with (n = 37) or without (n = 48) anti-DNase I showed that the former group had higher IgG serum levels (2293.2 ± 666.2 vs 1483.9 ± 384.6 mg/dL, p = 0.0001) and greater rate of non-drug-induced leukopenia (43% vs 19%, p = 0.02). A multivariate logistic regression analysis identified that only IgG levels were independently associated with anti-DNase I.
We describe a high frequency of anti-DNase I antibodies in pSS patients associated with higher serum IgG levels. The lack of this reactivity in RA patients without sicca symptoms suggests that this antibody may be helpful in the differential diagnosis of these diseases.