Interleukin-4 in rheumatoid arthritis patients with interstitial lung disease: a pilot study

BACKGROUND & OBJECTIVES: Interstitial lung disease (ILD) is a progressive complication in patients with rheumatoid arthritis (RA). Although the precise mechanisms of ILD are not fully understood, Th2 cytokines, especially interleukin (IL)-4 may play an important role in the processes of fibrosis. We, therefore, investigated the role of Th2 cytokines, including IL-4, IL-13 and IL-5 in RA patients with or without ILD. METHODS: Serum samples were obtained from 63 patients with RA. Among them, 29 RA patients had ILD while the remaining 34 patients were without ILD. The bronchoalveolar lavage fluids (BALF) from 11 RA patients with ILD and eight patients without ILD were also collected. Enzyme-linked immunosorbent assay (ELISA) was used to analyze the levels of IL-4, IL-13 and IL-5 both in serum and in BALF. RESULTS: The levels of IL-4 were increased in the serum and BALF of RA patients with ILD compared with RA patients without ILD. There were no differences in the levels of IL-13 and IL-5 among the different groups. INTERPRETATION & CONCLUSION: The present results indicate that IL-4 seems to play an important role in the development of ILD in patients with RA.