Secreted cytokine-like protein (PubMed:12847263). Binds to the scavenger receptor MARCO (PubMed:12847263). Can also bind to pathogens including the Gram-positive bacterium L.monocytogenes, the Gram-negative bacterium P.aeruginosa, and yeast (PubMed:12847263). Strongly inhibits phospholipase A2 (PLA2G1B) activity (PubMed:24213919). Seems to have anti-inflammatory effects in respiratory epithelium (By similarity). Also has anti-fibrotic activity in lung (PubMed:24213919). May play a role in fetal lung development and maturation (PubMed:24213919). Promotes branching morphogenesis during early stages of lung development (PubMed:24213919). In the pituitary, may inhibit production of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) (By similarity). Homodimer; disulfide-linked (PubMed:24213919). Monomer (PubMed:24213919). Interacts with APOA1 (PubMed:12847263). Highly expressed in lung and trachea (PubMed:12406855, PubMed:12175512, PubMed:12847263). Detected throughout the airway epithelium in lung, with slightly higher expression in large airways (PubMed:12406855). Found in lung submucosal gland acinus where it localizes to serous-like cells (PubMed:12406855). Probably expressed in club/Clara cells of the bronchioles (PubMed:12847263). Not detected in other tissues tested (PubMed:12847263). Expressed in fetal lung. Belongs to the secretoglobin family. UGRP subfamily.