Airway epithelial cells contribute to the first line of mucosal defense by secretion of antimicrobial peptides and antimicrobial lipids, including the cholesteryl ester (CE) cholesteryl arachidonate. Sterol O-acyltransferase 1 (SOAT1) is a key enzyme for CE biosynthesis. However, little is known about the regulation of the lipid-mediated arm of innate host defense. Polarized human bronchial epithelial cells (HBE) were incubated for 6 h with 100 ng/mL LPS, 10 μg/mL peptidoglycan (PG), 25 μg/mL PamCys3, and solvent control. SOAT1 mRNA was quantified by qRT-PCR with duplexing and RPLP0α as housekeeping gene. Lipid content of apical HBE secretions was analyzed by rpHPLC. SOAT1 expression was blocked with siRNA/lipofection. Antibacterial activity of HBE secretions was assessed by a 3 h colony forming unit assay with Pseudomonas aeruginosa (PA). SOAT1 gene expression was significantly increased by LPS (14.6 ±11.4, means ± SD, n=4, p=0.037). Stimulation with PG and PamCys3 increased SOAT1 expression by ~ 4- and 2-fold, respectively. Secretions from LPS-stimulated HBE showed an increase of total lipids including CA by ~30-50%. Selective inhibition of SOAT1 mRNA expression by 80% reduced the antibacterial activity of HBE whereby PA showed enhanced bacterial growth reaching >170% of the controls. These data suggest that SOAT1 is regulated by conserved innate immunity pathways and further support the role of antimicrobial lipids as effector molecules in mucosal airway defense.