Cell Communication & the Immune System

Instructor: Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

In this lesson, we'll be exploring the cellular communication that happens when you get sick. You'll understand what cells are involved in an immune response and how they coordinate their attack on pathogens in your body.

What Is an Immune Response?

Remember having a cold? The stuffy nose, sore throat, and cough can put a real damper on your weekend activities. Have you ever stopped to think what happens in your body while you're sick? Although you might feel terrible at first, your immune system, a collection of cells and tissues, works day and night to defend your body. Your immune system is made of a variety of immune cells. Macrophages are general soldiers. They patrol your body, looking for invaders to engulf and destroy. Leukocytes are specialists and adapt to a specific pathogen. B-cells make antibodies, T-cells directly attack pathogens, and natural killer (NK) cells attack infected cells.

Like an army, these cells need to talk to each other to coordinate an immune response or an attack on the invading pathogen. However, your cells don't have walkie-talkies like soldiers. They use two main types of communication to mount their response, chemical communication and direct cell-to-cell communication. Let's look at how these types of communication work in detail next.

Chemical Communication

The main chemicals of the immune system are called cytokines. Immune cells make these chemicals and send them out into the body to activate and recruit other immune cells. Cytokines are like a message saying, ''Hey, there's an infection. We need your help!''

Cytokines spread through the body and attach to the surface of other immune cells at proteins called receptors. The receptors signal the cell to change what proteins it makes and its behavior to help fight the infection. There are hundreds of cytokines in the body, which can be divided into four main categories: interleukins, interferons, chemokines and tumor necrosis factors.

Cytokines are used for cell communication from a distance


Interleukins allow for communication between leukocytes. Interleukins are used to activate T-cells and B-cells, snapping them into action for the battle. They also increase the production of lymphocytes, which increases the immune response. You can think of this effect as recruitment in the army. When there is a war, recruitment increases, making a bigger army to fight the enemy.


Like other cytokines, there are several types of interferons. However, all interferons are secreted in response to a viral infection. Interferon-I is made by nearly all cells in the presence of a virus, but interferon-II is made specifically by NK cells and T-cells. Interferons cause infected cells to fight the virus more efficiently and activate T-cells and NK cells to attack.


Picture cooking a delicious dinner. The smells from the kitchen might attract quite a few people in your house. Perhaps surprisingly, your immune system uses a similar strategy to attract lymphocytes to the site of infection. Macrophages and other immune cells secrete chemicals called chemokines. These chemicals act as a chemical attractant, bringing immune cells to the area just like the smell of food brings all your siblings to the kitchen.

Tumor Necrosis Factors

During an infection, tumor necrosis factors are secreted by macrophages, B-cells, T-cells, and natural killer cells (NK). This cytokine induces an inflammatory response, increasing blood flow and recruiting white blood cells to the area. It is also involved in cell self-destruction during an infection.

Cell-to-Cell Communication

Chemical communication is like sending long distance messages between soldiers. Cell-to-cell communication is more like a special-ops unit, where members communicate intimately on a mission.

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