Agglutinins & Agglutinogens

Andrea Taktak, Bridgett Payseur
  • Author
    Andrea Taktak

    Mrs. Taktak is in her 21st year of teaching high school science courses. She has designed curriculum and lessons for Forensic Science and Sports Medicine, and has taught Honors Biology, Anatomy and Physiology, Physical Science, and Environmental Science. Mrs. Taktak is a Master Teacher with a Teacher Leader Endorsement and has a Masters Degree in Education from Graceland University as well as a Bachelors of Science degree from Northern Kentucky University. She also most recently earned her Ohio Certified Volunteer Naturalist certificate while studying and volunteering at the Cincinnati Nature Center.

  • Instructor
    Bridgett Payseur

    Bridgett has a PhD in microbiology and immunology and teaches college biology.

Understand what agglutinin is by learning the agglutinin definition. Also, learn what agglutinogens are and understand how they are different from agglutinins. Updated: 03/10/2022

Table of Contents


What Is Agglutinin?

The body's immune system does a fabulous job of picking up on cells or toxins that are not supposed to be present. Part of the immune response uses agglutinin to rid the body of unwanted cells, such as pathogenic bacteria, viruses, fungi, or other invaders in a process called agglutination. What is agglutinin? Agglutinin is a special kind of antibody that binds foreign cells together, forming a clump. The process of forming the clump is called agglutination. Other antibodies then bind to the clumped foreign matter in the blood and mark it for destruction.

Function and Working of Agglutinin

Agglutination is the part of an immune response that tags or marks the grouped cells and makes them an easy target. For agglutination to occur, the body must discover a pathogen or foreign material. An agglutinin (a special antibody) will specifically bind to the outer proteins of the foreign substance, causing the cells to stick together.

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  • 0:00 What Are Agglutinins?
  • 0:44 What Are Agglutinogens?
  • 1:18 Rejection
  • 2:27 Agglutination Uses
  • 3:28 Lesson Summary
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An agglutinogen is the foreign cell proteins (markers) that the body does not recognize and that trigger an immune response and lead to the production of agglutinins. Agglutinogens are often referred to as antigens. Both agglutinins and agglutinogens are made of proteins, but agglutinins are proteins produced by the body as part of an immune response, while agglutinogens are proteins produced by foreign cells or genetic material. Agglutinins bind to agglutinogens, which causes the process called agglutination. Another way to say this is that a body's antibodies bind to proteins on foreign cells called antigens.

Uses of Agglutination

Agglutination is used in the immune response for typical pathogenic material, but this process of clumping also occurs when the wrong blood types are mixed. If agglutination occurs in the bloodstream, it can be fatal. When agglutination occurs with incompatible blood types, the clumping effect is observable. This process is how blood types are determined.

In the early 1900s, a scientist named Karl Landsteiner developed a blood typing test after several patients that received blood transplants died, and it was observed that the deceased patients' blood had agglutinated. Landsteiner discovered that there are four blood groups.

  • Type A blood: red blood cells that have A agglutinogens (antigens) on the surface of the cells. The blood plasma contains B agglutinins (antibodies).
  • Type B blood: red blood cells that have B agglutinogens (antigens) on the surface of the cells. The blood plasma contains A agglutinins (antibodies).
  • Type AB blood: red blood cells that have both A and B agglutinogens (antigens) on the surface of the cells. The blood plasma contains no agglutinins (antibodies).
  • Type O blood: red blood cells that have NO agglutinogens (antigens) on the surface of the cells. The blood plasma contains both A and B agglutinins (antibodies).

If a person with type A blood were to receive type B donor blood, the B agglutinins (antibodies) present in the blood plasma would bind to the B agglutinogens (antigens) on the surface of the cells, causing agglutination. To conduct a blood typing test, a drop of blood can be mixed with A and B agglutinins to look for clumping. These agglutinins are typically labeled as anti-A and anti-B. If a blood drop is mixed with anti-A serum and agglutination occurs, the blood type will be A. This is because the red blood cells have A agglutinogens (antigens) on the surface of the cells that have clumped with the anti-A agglutinins.

A second blood cell agglutinogen, called the Rhesus factor (Rh factor), is present on about half of human blood cells. If this agglutinogen is present, a person is said to be positive. If it is not present, the person is said to be negative. People that are negative for the Rh factor will sometimes have agglutinins in the blood plasma; therefore, agglutination may occur if an Rh-negative individual receives blood from an Rh-positive donor.

Observe the different ABO blood groups and their agglutinins and agglutinogens.

An image of ABO blood groups in chart form.

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Frequently Asked Questions

What is an agglutinin or agglutinogen?

Agglutinins and agglutinogens are both proteins that react together during an immune response. Agglutinins are also known as antibodies. Agglutinogens are also known as antigens. When these bind together, clumping occurs, which is called agglutination.

What is cold agglutinin disease?

Cold agglutinin disease (CAD) is a rare autoimmune disease. With this disease, a person that is exposed to cold temperatures (below 39 degrees) will experience an immune response that attacks the body's own red blood cells.

What are examples of agglutinins?

Agglutinins are special antibodies involved in an immune response. A common example is ABO agglutinins (antibodies) found in the blood plasma. There are also Rh factor agglutinins. Both types of agglutinins are found in the blood and can agglutinate with an incompatible blood type.

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