Has bactericidal activity. May act as a ligand for C-C chemokine receptor CCR6. Positively regulates the sperm motility and bactericidal activity in a CCR6-dependent manner. Binds to CCR6 and triggers Ca2+ mobilization in the sperm which is important for its motility (PubMed:25122636). Monomer (PubMed:23938203). Homodimer (PubMed:23938203). Associates with tumor cell membrane-derived microvesicles (PubMed:23938203). Blood plasma. Sperm. Highly expressed in the lower head and midpiece of sperm. Significantly reduced levels found in the sperms of asthenozoospermia and leukocytospermia patients (at protein level). Belongs to the beta-defensin family.