Researchers based in England, China, Taiwan, and the U.S. have identified a sugar, located on a human ovum, that is recognized by human sperm. The identity of the sugar, called sialyl Lewisx, is an essential piece of information required to unscramble the biochemical steps taken during fertilization and may lead to a better understanding of infertility and better treatments for it. Like the eggs of many other animal species, human ova are dressed in a thick protective coat of proteins and sugars called the zona pellucida (ZP). The team confirmed that sperm recognize the sialyl Lewisx sugars on the egg by showing that sperm-egg binding could be inhibited when the sialyl Lewisx sugar was cloaked by antibodies. The sugar is involved in helping white blood cells exit the bloodstream to get to infected tissue, but it is typically only a very minor constituent on egg.