Decapacitation factor (DF) is composed of factors in seminal plasma which modulates the fertilizing ability of spermatozoa. The activity is achieved by interaction between cholesterol, phospholipids and fibronectin-like substances and delivered via small vesicles in seminal plasma. DF prevents onset of capacitation.
Physiologically it is achieved through spermatozoal membrane stabilization by maintaining physiological cholesterol/phospholipid ratio. The study of DF is essential to understand unexplained male infertility and has possible role in reversible male contraception. Ejaculates from animals when purified have obtained DF. Such ejaculates when injected into the uterus with sperms decrease the fertilization by decreasing efficiency of capacitation of spermatozoas.
In natural conditions, uterus have the ability to inactivate or remove overwhelmed DF, serving a purpose. In vitro incubation of DF with uterine fluids has been reported to have failed to destroy DF activity. The DF factors can be removed from the seminal plasma by gentle centrifugation and can be added back. Some known DF and their study have shown to be aniinic polypeptide with MR~40,000, stable to heating at relatively high temperature and stable to enzymes and pH.