IPF-HLFs secrete high levels of IL-6 and activate the STAT3 pathway in normal HLFs. Human lung fibroblasts from patients with IPF (IPF-HLF) or control donors (N-HLF) and were cultured and their supernatants (SN) were collected. IL-6 levels in the SN were measured by ELISA-based array a. IL-6 mRNA levels from N-HLF and IPF-HLF cells were measured by qPCR b SN from IPF-HLFs was added to N-HLF for further cultures. The effect of the IPF-HLF-SN on N-HLF pSTAT3-Y705 (30 min, c-d, pSTAT3-S727 (24 h, e and total protein levels of SOCS3 (24 h, f were analyzed by western blotting. c Representative western blots for Figs. D-F. *p < 0.05, **p < 0.01, and ***p < 0.001. (n ≥ 4).