Indeed, IL-17 gene expression is enhanced in lungs of both IPAH and SSc-PAH compared to idiopathic pulmonary fibrosis (IPF) and pulmonary fibrosis associated SSc (SSc-PF) (68), this IL-17 may be expressed by cells in TLOs as well as in tissues outside of TLOs. Here, IL17A is linked to pulmonary fibrosis.