MUC5B and idiopathic pulmonary fibrosis: MUC5B was robustly expressed and colocalized with the IPF GWAS meta-analysis and the UKBB IPF GWAS in SCGB1A1+/MUC5B+ and SCGB3A2+ secretory cells, implicating these as the most likely cell types in which the risk variant functions (Supplementary Figs. 17 and 18).