DEFB106A encodes defensin beta 106A, a cationic antimicrobial peptide belonging to the beta-defensin family characterized by six conserved cysteine residues 1. This gene is predominantly expressed in the epididymis, with region-specific localization in the corpus segment 2. DEFB106A contributes to innate immunity through antimicrobial and antiviral mechanisms, binding to glycosaminoglycans including heparin and competing for chemokine receptor CCR2 binding sites to modulate leukocyte recruitment 3. The gene also demonstrates salt-dependent antimicrobial activity against Gram-negative and Gram-positive bacteria 1. In reproductive physiology, DEFB106A expression in the epididymal epithelium is critical for creating the luminal environment necessary for spermatozoal maturation 1. Notably, DEFB106A expression is significantly downregulated in the caput epididymidis of men with nonobstructive azoospermia compared to fertile controls, suggesting its role in male fertility 4. This downregulation occurs alongside alterations in water and ion transport gene expression, indicating broader disruption of epididymal function in infertile patients 4. The coordinated expression of multiple beta-defensin isoforms, including DEFB106A, suggests cooperative regulation of urogenital innate immunity 1. However, clinical applications of beta-defensin therapy require caution, as adenovirus-mediated HBD6 expression paradoxically exacerbated viral infection in vivo 5.