This video we're going to begin our lesson on cell communication by focusing on surface receptors and adhesion molecules. Cell surfaces contain many types of receptor proteins, as well as many types of adhesive molecules. These receptor proteins and adhesive molecules are important for communication during an infection. They allow cells of the immune system to signal an infection and to migrate to the infected location within the body. We will first focus on cell surface receptors and then later on adhesive molecules.
Cell surface receptors, or just surface receptors, are proteins on the cell surface that specifically allow the cell to sense and respond to external signals or environmental signals. The surface receptor protein spans the entire cytoplasmic membrane, connecting the outside of the cell to the inside, allowing the cell to respond to external signals. Each specific surface receptor has a specific molecule that it will bind to. Surface receptors do not respond to all molecules; they only respond to very specific molecules. These molecules we refer to as a ligand. A ligand is a molecule that binds to a surface receptor, and when it binds, it can elicit a response inside of the cell, allowing the cell to respond to the external signal.
Cells are capable of altering the number and types of surface receptors they have. This allows the cells to change their response rates and sensitivity to a certain ligand. Below in this image, we're showing you our map of the lesson on the scanning systems of innate immunity, which serve as security cameras. We are specifically focusing on cell communication and the surface receptors in this video. Notice how on the left-hand side we are showing a signaling cell that is creating some kind of signal. This signal, or ligand, can bind to the receptor proteins found on the cell surface receptors, shown here in purple. This is the recipient cell. Only cells that have the specific cell receptor can respond to this specific ligand.
The binding of the ligand to the cell surface receptor triggers a cascade of events, causing one substance to lead to another, ultimately leading to some kind of cellular response, allowing the recipient cell to respond to external signals. This is how cell communication can occur, and it is very important for immunity. This concludes our brief introduction to the cell surface receptors that are important for cell communication. In our next lesson video, we will talk more about the adhesion molecule. I'll see you all in our next video.