key term - Sialyl Lewis X

Definition

Sialyl Lewis X is a carbohydrate structure, specifically a glycan, that plays a crucial role in cell-cell interactions and immune responses. It is a specific ligand for selectins, which are proteins that mediate the adhesion of white blood cells to endothelial cells during inflammation. This structure is particularly important in the process of leukocyte rolling and extravasation, which are key steps in the immune response.

5 Must Know Facts For Your Next Test

1. Sialyl Lewis X is specifically recognized by selectins, such as E-selectin and P-selectin, which are expressed on activated endothelial cells.
2. The presence of sialyl Lewis X on leukocytes enhances their ability to migrate to sites of inflammation by promoting adhesion to the endothelium.
3. This glycan structure is synthesized through specific enzymes, including fucosyltransferases and sialyltransferases, which modify precursor glycans.
4. Sialyl Lewis X also has implications in cancer biology, as some tumors exploit this glycan for increased metastasis by evading immune surveillance.
5. Alterations in the expression of sialyl Lewis X can affect inflammatory responses and may contribute to various diseases, including autoimmune disorders.

Review Questions

• How does sialyl Lewis X facilitate leukocyte rolling and adhesion during an immune response?
  • Sialyl Lewis X acts as a ligand for selectins on endothelial cells, allowing leukocytes to bind loosely and roll along the vessel walls. This interaction is crucial during inflammation, where leukocytes need to exit the bloodstream and enter tissues. The binding between sialyl Lewis X and selectins slows down the leukocytes, enabling them to respond to signals that promote further adhesion and eventual extravasation into the inflamed tissue.
• Discuss the implications of sialyl Lewis X in cancer metastasis and its role in immune evasion.
  • In cancer biology, sialyl Lewis X can promote tumor metastasis by enabling cancer cells to adhere to endothelial cells, facilitating their entry into the bloodstream and spread to distant sites. This glycan's ability to mimic normal leukocyte behavior can also help tumors evade detection by the immune system. By exploiting pathways usually reserved for immune cells, tumors can enhance their survival and growth in a hostile environment.
• Evaluate how changes in the expression of sialyl Lewis X might impact inflammatory diseases and therapeutic strategies.
  • Changes in sialyl Lewis X expression can significantly influence inflammatory responses and may contribute to various conditions like autoimmune diseases or chronic inflammation. Understanding these alterations allows researchers to develop targeted therapies aimed at modulating sialyl Lewis X interactions. For instance, therapies could be designed to inhibit its binding to selectins, reducing inappropriate leukocyte trafficking during inflammation, which could help manage symptoms in chronic inflammatory diseases.

Related terms

Selectins:

A family of cell adhesion molecules that bind to carbohydrates on the surfaces of other cells, facilitating the rolling and adhesion of leukocytes during inflammation.

Glycoconjugates: Molecules that consist of carbohydrates covalently linked to proteins or lipids, playing vital roles in cellular recognition and signaling.

Leukocyte Extravasation: The process by which white blood cells move out of the circulatory system and into tissues, critical for mounting an immune response to infection or injury.