The correlation of IP-10 levels in NLF with BALF in other chronic airway diseases and in airway epithelial culture in the absence of CFTR expression suggests that the elaboration of IP-10 in airways-derived fluid is not specific to CF, although this disorder may be more prone to heightened IP-10 expression, as also suggested by some but not all of the in vitro studies presented here. The gene discussed is CXCL10; the disease is cystic fibrosis.