Characterization of β-defensin 42 expressed in principal cells at the initial segment of the rat epididymis

β-defensins, preferentially expressed in male reproductive tracts, particularly in the testes and epi- didymis with region-specific patterns, play an important role in both innate immunity and sperm fer- tility. Expressed in the caput region of epididymis, β-defensins have been known to contribute to innate immunity, sperm motility initiation, and maintenance. However, β-defensins of the initial region remain to be uncharacterized. In this study, rat β-defensin 42 （Defb42） was revealed to be exclusively located in the principal cells at the initial segment of the rat epididymis and its sperm＇s acrosome. Furthermore, the expression of Defb42 was dependent on luminal testicular factors and developmental phases. The recombinant Defb42 was predominantly antimicrobial not against Candida albicans, but against Escherichia coli and Staphylococcus aureus. Based on these findings, Defb42 was suggested to play a dual role in sperm fertility and host defense in rat epididymis.