CD109 and congenital rubella syndrome: Quercetin, a plant-derived flavonoid, exhibits various pharmacological effects.[74] It may be beneficial for AR treatment by balancing the Th1/Th2 and Treg/Th17 ratios and inhibiting the NF-κB pathway.[75] Furthermore, quercetin has been shown to reduce cell apoptosis and attenuate CRS progression by inhibiting nasal mucosal inflammation and epithelial barrier dysfunction, thus supporting its potential as a therapeutic agent for CRS.[76] These findings align with our research on the quercetin–CD109 interaction.