What Are Cytokines? - Definition, Types & Function

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  • 0:02 Cytokines
  • 1:38 Chemokines
  • 2:20 Interferons & Interleukins
  • 3:37 Lymphokines & TNF
  • 4:39 Lesson Summary
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Lesson Transcript
Instructor: Rebecca Gillaspy

Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.

Cytokines are a group of proteins made by the immune system that act as chemical messengers. Learn about the functions of different cytokines, including chemokines, interferons, interleukins, lymphokines and tumor necrosis factor.


Your body is made up of trillions of cells. These cells are basic units of life; they carry out all the vital functions that keep you alive. But did you know that your cells lead very active social lives? Take the cells of your immune system, for instance. These cells are constantly sending out signals to let other cells know what's going on. To communicate, your immune cells use cytokines, which are a group of proteins secreted by cells of the immune system that act as chemical messengers.

Cytokines released from one cell affect the actions of other cells by binding to receptors on their surface. You can think of these receptors as mailboxes. They receive the cytokine's chemical message, and then the receiving cell performs activities based on that message.

There are different types of cytokines, including chemokines, interferons, interleukins, lymphokines and tumor necrosis factor. They can act alone, work together or work against each other, but ultimately the role of cytokines is to help regulate the immune response. Cytokines are involved in many aspects of inflammation and immunity. In fact, you can blame the different cytokines for triggering some familiar symptoms that arise when your body fights an infection, such as fever, inflammation and pain. Let's take a look at the different types of cytokines and their functions.


Chemokines are a type of cytokines that call in cells to the site of infection. You might recall that the ability to call in other cells using a chemical message is a process referred to as chemotaxis. This fact shows us how this type of cytokine gets its name; chemokines induce chemotaxis. Chemokines are the coordinators of the battle. For example, when a foreign substance is detected, chemical orders are sent out to immune cells, including various white blood cells. These cells then travel toward the area to eliminate the threat.

Interferons & Interleukins

Interferons are proteins that inhibit viruses from replicating. If a cell gets invaded by a virus, it releases interferons. This signals other cells to put up their shields so the virus does not spread. So, interferons interfere with the spread of a virus. Interferons also activate natural killer T-cells. These cells further the fight against the virus by destroying infected cells.

Interleukins are proteins that regulate immune and inflammatory responses. They are produced mainly by white blood cells. Their job is to send signals out to other white blood cells telling them they need to report for duty. The name interleukins is easy to recall if you remember that the first part of the word, 'inter,' means between or communication between cells, and the second part, 'leukins,' refers to leukocytes, which is the formal name for white blood cells. So, interleukins create communication between leukocytes. There are many different types of interleukins, and each has a role to play in the immune system. These functions include the growth, maturation and activation of immune cells.

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