Cutting Edge: Anti-TIM-3 Treatment Exacerbates Pulmonary Inflammation and Fibrosis in Mice [CUTTING EDGE]

Promising results of immune checkpoint inhibitors have indicated the use of immunotherapy against malignant tumors. However, they cause serious side effects, including autoimmune diseases and pneumonitis. T cell Ig and mucin domain (TIM)-3 is a new candidate immune checkpoint molecule; however, the potential toxicity associated with anti–TIM-3 treatment is unknown. In this study, we investigated the pathological contribution of anti–TIM-3 mAb in a bleomycin-induced lung inflammation and fibrosis model. Anti–TIM-3–treated mice showed more severe inflammation and peribronchiolar fibrosis compared with control IgG-treated mice. Anti–TIM-3 mAb was associated with increased numbers of myofibroblasts, collagen deposition, and TGF-β1 production in lungs. TIM-3 expression was only detected on alveolar macrophages that protect against fibrosis by apoptotic cell clearance. Treatment with anti–TIM-3 mAb inhibited the phagocytic ability of alveolar macrophages in vivo, resulting in the defective clearance of apoptotic cells in lungs. In summary, anti–TIM-3 mAb treatment might cause pneumonitis and it should be used with caution in clinical settings.

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