In keeping with our finding of increased LOXL expression together with increased LH2 expression in IPF tissue, we identified an increase in mature hydroxyallysine-derived cross-links in IPF lung tissue, consistent with a previous report of an increase in mature DPD cross-links in fibrotic lung tissue (Last et al., 1990). Here, LOXL1 is linked to idiopathic pulmonary fibrosis.