Treatment with imatinib results in reduced IL-4-producing T cells, but increased CD4+ T cells in the broncho-alveolar lavage of patients with systemic sclerosis

T cells, particularly those producing IL-4, are implicated in inflammation-mediated fibrosis. In our phase I/IIa open-label pilot study in 15 patients with scleroderma-interstitial lung disease (SSc-ILD), high-dose imatinib treatment showed modest improvement in lung function and skin score, but with several adverse events. Here, we investigated T cell phenotype and cytokine production in bronchoalveolar lavage (BAL) from patients enrolled in this trial. We found that IL-4+ T cells showed a stronger correlation with ground glass opacity (GGO) than fibrosis scores on lung high-resolution computer tomography scans. Frequencies of IL-4+ T cells also discriminated patients with high (≥ 20) versus low (< 20) GGO scores. Functional annotation clustering of proteins that correlated with T cells identified two major clusters that belonged to immune/inflammatory and wounding response. Repeat analyses after 1 year of treatment in 10 BAL samples, one each from the right middle and lower lobes of lung from 5 patients, showed that post-imatinib, IL-4+ T cells were profoundly reduced but CD4+ T cells increased, except in one patient who showed worsening of SSc-ILD. Post-imatinib increase in CD4+ T cells correlated with soluble ICAM-3 and PECAM-1 levels in BAL, which associated with the lack of worsening in SSc-ILD. Thus, imatinib might confer its therapeutic effect in fibrosis via re-directing T cell responses from type 2 to other, non-type 2 cytokine producing CD4+ T cells.