A secreted 25 kDa protein naturally expressed in airway epithelial tissues exhibits potent antimicrobial activity against bacteria and viruses, while also modulating immune responses and safeguarding ion channels from proteolytic cleavage. Its ability to regulate airway surface liquid and reduce biofilm formation has been demonstrated in preclinical models. Researchers have developed recombinant protein forms, specific antibodies, and ELISA assays to detect and quantify the protein, and have employed transgenic mice to assess its in vivo efficacy. These features collectively suggest significant utility in enhancing lung innate defenses against respiratory pathogens.