BPI fold-containing family A member 1 (BPIFA1)

BPI fold-containing family A member 1 (BPIFA1), also known as SPLUNC1 or PLUNC, is a secreted protein mainly produced by epithelial cells of the airway and salivary glands[1][2][3][4]. It belongs to the BPI/LBP/PLUNC superfamily, characterized by a bactericidal/permeability-increasing (BPI) fold, and functions as a key effector of the innate immune system. BPIFA1 exerts *antimicrobial*, *anti-biofilm*, and *immunomodulatory* effects in the respiratory tract by binding to bacterial molecules (e.g., lipopolysaccharides), altering surface tension in airway mucus, and regulating the epithelial sodium channel (ENaC), which helps maintain airway hydration and defense[1][2][3][4]. It also inhibits proliferation and biofilm formation of respiratory pathogens, attracts immune cells to infection sites, and suppresses pro-inflammatory cytokines in airway inflammation[2][3][4]. Dysfunction or loss of BPIFA1 is implicated in *cystic fibrosis* airway disease, some cancers (as a diagnostic or prognostic biomarker), and respiratory infections (including antiviral defense against influenza A virus)[1][2][3][4]. BPIFA1 is widely used as a biomarker of airway epithelial cell differentiation and disease state, but no direct drug interactions or therapeutics targeting BPIFA1 are currently established.

Other names

Palate, lung and nasal epithelium clone protein (PLUNC)Short palate, lung, and nasal epithelium clone 1 (SPLUNC1)Secretory protein in upper respiratory tracts (SPURT)Lung-specific protein X (LUNX)Nasopharyngeal carcinoma-related proteinTracheal epithelium-enriched proteinVon Ebner protein HlbA49G10.5Protein Plunc