TSLP and idiopathic pulmonary fibrosis: In the subgroup of stable IPF patients, IL-33 serum follow-up levels did not differ significantly from baseline levels (1.96 (1.66–2.36) pg/mL vs. 2.21 (1.38–2.73) pg/mL, respectively) as well as TSLP serum follow-up levels (16.25 (14.38–17.82) pg/mL) were not different from baseline levels (16.25 (10.32–23.75) pg/mL).