Has antimicrobial activity against E.coli (PubMed:11230693). Plays a role in the defense response in the male reproductive tract, contributing to sperm maturation, storage and protection (PubMed:11230693). Only expressed in epididymis (middle part of the caput). Its expression starts at 30 days of age, reaches a maximum during the sexually mature period, and then decreased in old rats. Belongs to the beta-defensin family.