CD40LG and idiopathic pulmonary fibrosis: This study showed that C3c, IgG, and IgM, but not IgA, were more strongly expressed in the injured alveolar epithelium of patients with DM-ILD than in patients with IPF (used as control patients), suggesting that C3c, IgG, and IgM are crucially involved in DM-ILD-related lung injury.