Selectins

Definition

Selectins are a family of cell adhesion molecules that play a crucial role in the process of cell adhesion and migration, particularly in the immune response. They facilitate the initial interactions between leukocytes and endothelial cells during inflammation, allowing white blood cells to migrate from the bloodstream to tissues. The function of selectins is vital for immune surveillance, tissue repair, and the overall inflammatory response.

5 Must Know Facts For Your Next Test

1. There are three main types of selectins: L-selectin (found on leukocytes), P-selectin (found on activated platelets and endothelial cells), and E-selectin (expressed on endothelial cells in response to inflammatory stimuli).
2. Selectins recognize specific carbohydrate ligands on the surface of other cells, which is essential for rolling adhesion of leukocytes as they migrate through blood vessels.
3. The interaction between selectins and their ligands is relatively weak, allowing leukocytes to roll along the endothelium before firmly adhering to the vessel wall through integrins.
4. Selectins play a critical role in various physiological processes beyond inflammation, including tissue homeostasis and development.
5. Dysfunction or altered expression of selectins has been associated with various diseases, including chronic inflammatory conditions and cancer metastasis.

Review Questions

• How do selectins contribute to the process of leukocyte adhesion during inflammation?
  • Selectins facilitate the initial contact between leukocytes and endothelial cells by recognizing specific carbohydrate ligands on leukocyte surfaces. This interaction allows leukocytes to roll along the endothelial lining of blood vessels, which is a critical first step in their migration to sites of inflammation. The weak binding mediated by selectins allows leukocytes to decelerate and prepare for stronger adhesion through integrins, ensuring they can effectively exit the bloodstream.
• Discuss the differences between the three types of selectins and their specific roles in immune response.
  • L-selectin is primarily found on leukocytes and is involved in their homing to lymphoid tissues. P-selectin is expressed on activated platelets and endothelial cells during inflammation, mediating the initial rolling of leukocytes. E-selectin is upregulated on endothelial cells in response to inflammatory cytokines, enhancing leukocyte recruitment at inflamed sites. Each type of selectin plays a unique role in orchestrating the various steps of immune response by regulating how effectively leukocytes adhere to and migrate through blood vessels.
• Evaluate the implications of altered selectin expression in disease states such as cancer or chronic inflammation.
  • Altered expression of selectins can have significant implications in diseases like cancer and chronic inflammation. In cancer, increased expression of selectins can facilitate tumor cell adhesion to blood vessel walls, promoting metastasis by aiding in tumor cell extravasation into distant tissues. In chronic inflammatory conditions, dysregulated selectin activity can lead to excessive leukocyte recruitment, contributing to tissue damage and worsening inflammation. Understanding these alterations offers potential therapeutic targets for treating these diseases by modulating selectin function.

Related terms

Leukocytes: White blood cells that are essential components of the immune system, involved in protecting the body against infections and foreign invaders.

Endothelial Cells: Cells that line the blood vessels and lymphatic vessels, playing a key role in regulating vascular functions and facilitating the movement of substances across the vascular barrier.

Cell Adhesion Molecules (CAMs): A group of proteins located on the cell surface that mediate the interactions between cells and their surrounding environment, including adhesion, migration, and signaling.