Based on limited published evidence, DEFB135 is a defensin with antibacterial activity that participates in innate immune responses through membrane destabilization and killing of microbial cells. A 2025 Mendelian randomization study identified DEFB135 as a shared protective circulating protein against both heart failure and atrial fibrillation 1, suggesting potential cardiovascular protective functions beyond antimicrobial immunity. DEFB135 is located within the 8p23.1 critical region associated with congenital diaphragmatic hernia and cardiac defects 2, though its specific role in these conditions remains unclear.