Has antibacterial activity against Gram-positive bacterium S.pneumoniae Serotype 14. Is also active against Gram-negative bacteria M.catarrhalis 1857, and non-typeable H.influenzae strains 86-028NP and 1128. Has antifungal activity against C.albicans. May have a role in maintaining sterility in the middle ear (PubMed:14996845). 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 (By similarity). Monomer. Homodimer. Associates with tumor cell membrane-derived microvesicles. Highly expressed in tongue, nasopharyngeal mucosa and skin, and to a lower extent in the Eustachian tube, lung and trachea. Belongs to the beta-defensin family.