IL9 and fibrosis: Considering fibrosis status in BA patients, plasma IL-7 levels were found to be significantly higher in BA patients with fibrosis than those in non-fibrotic patients (P = 0.026), and no significant differences in plasma levels of remaining inflammatory cytokines including IL-1β, IL-6, IL-8, IL-9, and TNF-α between fibrotic and non-fibrotic groups were observed (Fig 3).