Which of the following is not true about selectins?

Selectins are a type of cell adhesion molecule that plays a critical role in the adhesion of leukocytes (white blood cells) to the endothelium during inflammatory responses. Each statement can be evaluated for its accuracy regarding selectins.

Selectins are indeed expressed on the surface of endothelial cells during inflammation, facilitating the initial capture and rolling of leukocytes along the blood vessel walls. This is a fundamental component of the immune response, allowing immune cells to exit the bloodstream and migrate to sites of injury or infection.

They are also calcium-dependent for their function. Selectins require Ca²⁺ ions for their binding interactions because their structure and binding mechanisms are influenced by the presence of calcium, which stabilizes the selectin-carbohydrate interactions.

Selectins specifically bind to carbohydrate ligands on the surface of leukocytes. This binding supports the rolling interaction of leukocytes over the endothelium, essential for their subsequent migration into tissues.

The correct answer identifies that the statement about selectins being transmembrane proteins that mediate cell-cell adhesion through homophilic bonding is not true. This is because selectins actually engage in heterophilic interactions, where selectins on one cell interact with carbohydrate ligands on another cell, rather than adhering to the same type