CHIA (chitinase acidic) is a secreted enzyme that degrades chitin and chitotriose polymers, primarily functioning in innate immune defense against pathogenic organisms. The protein exhibits chitinase activity and catalyzes chitin catabolic processes, with carbohydrate binding essential for its biological functions [UniProt]. CHIA plays a central role in Th2-mediated immune responses and IL-13-driven inflammation by stimulating chemokine production from pulmonary epithelial cells while simultaneously protecting lung epithelial cells from apoptosis through AKT1 phosphorylation [UniProt]. These cytoprotective and inflammatory functions depend on intact carbohydrate-binding capacity, as demonstrated by inhibition with allosamidin [UniProt]. Clinically, CHIA variants are associated with asthma susceptibility. The rs10494132 polymorphism represents a risk factor for asthma development, particularly in Asian populations and children (T allele: OR=1.476, P=0.017), whereas related CHI3L1 variants show protective associations in Caucasians 1. CHIA's dual role in pathogen defense and inflammatory regulation positions it as a key mediator in respiratory immune homeostasis, with genetic variation influencing disease predisposition.