Analysis of cytokines in bronchoalveolar lavage fluid in patients with checkpoint inhibitor pneumonitis and pulmonary infection: A case–control study

BACKGROUND: The discovery of immune checkpoint inhibitors (ICIs) is a breakthrough in the field of cancer therapy. However, ICIs may cause immune‐related adverse reactions, including checkpoint inhibitor‐related pneumonitis (CIP). The aim of this study was to investigate cytokines in bronchoalveolar lavage fluid (BALF) of patients with CIP compared with patients with pulmonary infection and patients with cancer. METHODS: We retrospectively analyzed 34 cytokine levels and T cell subsets in BALF supernatant samples from ICI‐treated patients with CIP (n = 13), pulmonary infection (n = 10), and progressive cancer (n = 12). Cytokine levels and T cell subsets were compared among the three groups of patients. RESULTS: We observed significantly higher levels of IFN‐γ‐induced protein 10(IP‐10) (p = 0.002), and percentage of CD3 + CD8 + T cells (p = 0.020) in BALF of patients with CIP compared with the other two groups. However, we found significantly lower levels of interleukin‐21 (p = 0.008) in BALF of patients with progressive disease compared with the other two groups. CONCLUSIONS: Cytokine profile and character of cell subsets in BALF was helpful for the differential diagnosis of CIP. IP‐10 may play an important role in pathophysiology for CIP and also be a potential therapeutic target.