To clarify the clinical significance of autoantibodies (auto-Ab) to interleukin-1alpha (IL-1alpha) in rheumatoid arthritis (RA) with interstitial lung disease (ILD), we examined the IL-1alpha auto-Ab level in serum of patients with RA with/without ILD.
We investigated the level of IL-1alpha auto-Ab in serum of 70 patients with RA with/without ILD and 40 control patients (CP). Levels of IL-1alpha auto-Ab were measured by radioimmunoassay, and serum was regarded as IL-1alpha auto-Ab positive at an auto-Ab level of more than 5 ng/mL.
Interleukin-1alpha auto-Ab was detected in the serum of 30 out of 70 RA patients (42.9%), and six out of 40 CP (15%) (P < 0.05). Interleukin-1alpha auto-Ab were detected in the serum of 18 out of 32 patients with RA with ILD (56.2%) and 12 out of 38 patients with RA without ILD (31.5%). The positive rate of these autoantibodies in RA with ILD was significantly higher than that in RA without ILD (P < 0.05). Although C-reactive protein, immunoglobulin G, rheumatoid factor and rheumatoid arthritis particle agglutination levels in serum from patients with RA with ILD were not significantly different between the IL-1alpha auto-Ab-positive and -negative groups, the lactate dehydrogenase level (LDH) and AaDO, in the IL-1alpha auto-Ab-positive group were significantly higher than those in the negative group (LDH: P < 0.001, AaDO2: P < 0.05).
These results suggest that IL-1alpha auto-Ab are generated in response to the immunoinflammatory process of ILD in RA, and these autoantibodies may neutralize and regulate the IL-1alpha activity.