Sialyl Lewis^X oligosaccharide

Article By:

Clark, Gary F. Division of Reproductive and Perinatal Research, Department of Obstetrics, Gynecology, and Women’s Health, University of Missouri, Columbia, Missouri.

Last reviewed:2013

DOI:https://doi.org/10.1036/1097-8542.YB130007

Sexual reproduction requires the physical joining of a male gamete (sperm) with a female gamete (egg) to generate a fertilized egg that is usually genetically distinct from its parents. The human egg consists of a single cell (oocyte) that is covered with a specialized coating known as the zona pellucida (ZP). Human fertilization begins when sperm bind to the ZP, penetrate this coating, and come into direct physical contact with the oocyte. A single sperm fuses with the oocyte, generating a fertilized egg (zygote). Another vital adhesion process is the binding of immune and inflammatory cells to the lining of blood vessels (endothelium) in tissues or organs that have become infected or injured. This interaction is required for these cells to respond to bacteria, viruses, parasites, and other organisms that can cause harm, known collectively as pathogens. Cancer cells released into the blood also bind to the endothelium, enabling them to migrate into tissues and organs at distant sites from the original tumor, where they initiate the growth of new tumors (metastases). This process of tumor spread is called metastasis. The sialyl Lewis^X oligosaccharide (SLe^X) and closely related carbohydrate sequences play a vital role in human sperm–egg binding, the movement of immune and inflammatory cells to the sites of infection and tissue injury, and metastasis.

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