Based on limited published evidence, DEFB123 is a beta-defensin gene located on chromosome 20.1 that encodes an antimicrobial peptide with antibacterial activity. The protein functions in innate immunity through membrane destabilization and killing of pathogenic organisms 1. DEFB123 is part of a cluster of defensin genes (DEFB119-DEFB123) with restricted expression in the male reproductive tract and androgen-dependent regulation, suggesting roles in reproductive specialization 1. DEFB123 expression is significantly downregulated in seminoma components of mixed testicular germ cell tumors compared to pure seminomas 2, indicating potential involvement in tumor progression.