MUC1 and interstitial lung disease: Interstitial pneumonia will promote the proliferation of type II alveolar epithelial cells, resulting in an increase in the KL-6 concentration, and this damage leads to an increase in vascular permeability, allowing KL-6 to enter the bloodstream; therefore, the concentration of KL-6 in the serum of patients with ILD increases [19, 20].