MUC1 and interstitial lung disease: Meanwhile, our study showed that compared with the CTD control group, CTD-ILD patients had significantly reduced lung function (FEV1%, FVC%, and DLCO%), significantly increased serum IL-6 levels, and a significant increase in KL-6, which is closely related to alveolar and capillary damage, activation of immune and inflammatory status, and fibrotic activity in ILD patients as mentioned in the existing literature [38–41].