DEFB4A (defensin beta 4A) is an antimicrobial peptide gene that serves as a critical component of innate immune defense at epithelial surfaces. The primary function involves broad-spectrum antimicrobial activity against Gram-negative bacteria, Gram-positive bacteria, and fungi including Candida albicans 1. The gene is locally inducible by inflammation and microbial contact, representing the first human defensin with this dynamic regulation 2. Mechanistically, DEFB4A expression is regulated through IL-17-dependent signaling involving IκBζ and Egr3 transcription factors, which are essential for antifungal defense in oral epithelium 3. The encoded protein also functions as a chemokine, binding CCR6 receptors to attract immune cells. Disease relevance includes upregulation in inflammatory conditions such as Crohn's disease, where DEFB4A expression increases in late-stage disease 4, and atopic eczema development 5. Clinical significance extends to wound healing, as KGF and DEFB4A show altered expression patterns in burn patients, with increased fibroblast expression but decreased keratinocyte expression correlating with burn severity 6. The gene exhibits considerable inter-individual variability in expression and copy number variation 7.