TGFB1 and pulmonary fibrosis: Therefore, circulating Th2 cells migrate to lung tissues due to the action of many chemokines and expressed Th2 cytokines, such as TGF-β1 [32], enhancing the processes underlying the development of pulmonary fibrosis, which might explain why the level of peripheral Th2 cells was lower and the Th1/Th2 ratio was higher in patients with pSS-ILD than in pSS-non-ILD patients, while the opposite results were found in the BLA samples from patients with idiopathic pulmonary fibrosis and SScFib+.