MMP8 and idiopathic pulmonary fibrosis: Knowledge gaps in the area of MMP-8 and IPF include: 1) which cells in the lung contribute to the elevated BALF MMP-8 levels in IPF patients; 2) whether MMP-8 levels in blood myeloid leukocytes are dysregulated in IPF patients; 3) which is the key form of the proteinase (soluble vs. membrane bound and active vs. latent MMP-8) present in IPF blood and lung samples; and 4) whether substrates that we have identified for MMP-8 in the fibrotic murine lung are also potential substrates for MMP-8 in human IPF lungs.