On the other hand, as already discussed above, members of the MMP family and YKL-40 have been shown to be increased in the airways of CF patients [10], [34], [35], [36], [37], [40], [50] and thus, it might well be speculated that the observed increased serum levels are indeed derived from the bronchial tree of CF patients. The gene discussed is CHI3L1; the disease is cystic fibrosis.