Figure 5.
The role of defensins in human reproduction. Defensins are widely distributed along the male and female reproductive tracts. Sperm are produced from the testis, mature in the epididymis and enter the female reproductive tract for fertilization. (A) During the maturation in the epididymis, β-defensins are loaded onto the sperm surface. (B) Defensins are cationic polypeptides, while cervical mucus proteins are negatively charged. Therefore, defensins can promote sperm to pass through the cervical mucus to the uterus. (C) DEFB126 can also form a protective shield on the surface of sperm to protect the sperm from immune recognition and binding by anti-sperm antibodies. (D) When the sperm reaches the isthmus of the fallopian tube, the DEFB126 on the surface of the sperm can mediate the combination of the sperm with the fallopian tube epithelium to form a sperm pool. When sperm capacitate, the surface DEFB126 falls off, the sperm is released from the isthmus of the fallopian tube, and the receptor of the sperm and oocyte on the surface are exposed to promote fertilization. (E) DEFB1 secreted from the uterine epithelium interacts with sperm chemokine receptor type 6 (CCR6) and causes Catsper-dependent Ca2+ influx to maintain movement.