Immunoglobulin-like Cell Adhesion Molecules

Immunoglobulin-like cell adhesion molecules, or Ig-CAMs, have a characteristic immunoglobulin protein fold in their multiple extracellular binding domains, called Ig-domains.

These Ig-domains allow the Ig-CAMs to function diversely across different tissue types.

For instance, neural or NCAMs expressed on neurons bind to each other via their Ig-domains to form homophilic interactions.

These interactions are involved in complex signaling pathways during neuronal differentiation and direct many contact-dependent processes, such as the growth of axons and dendrites.

In contrast, the Ig-domains of vascular or VCAMs, and intracellular or ICAMs, can bind different integrins — another type of cell adhesion molecule, thus exhibiting heterophilic interactions.

During an immune response, the vascular endothelium expresses these Ig-CAMs to recruit leukocytes from the bloodstream.

As the leukocytes slow down by selectin-mediated cell interactions, the integrins on their cell surface become activated.

This activation enables the integrins to firmly bind the Ig-CAMs on the endothelium and trigger various signaling cascades. The leukocyte finally passes between the endothelial cells to reach the destined tissue.