Learn about how red blood cell hemagglutination works and the factors involved in the process.
See how hemagglutination is used in the laboratory in an array of tests, from blood typing to the diagnoses of viral illness.
How Hemagglutination Works
Imagine you are trying to build a sand castle. You fill the castle mold with sand, turn it over, and whoops – no castle! What did you forget? Water! In order for the sand to stick together, you needed water. Once the right amount of moisture is added to the sand, then – tada! The perfect castle is born!The same principle applies to agglutination, which involves the clumping together of cells. Agglutination is often used by your body’s immune system to clump toxins or pathogens together.
Once congregated, these invaders can easily be inactivated by cells in the immune system.Just as you need water to make a sand castle stick, the immune system needs antibodies to make unwanted foreign bodies stick together. Antibodies are proteins made by the immune system that are very specific to what they attach and bind.
Antibodies are a key component in hemagglutination, or clumping together of red blood cells. To remember this long term, think of the prefix ‘hema’ meaning blood, and the ‘glu’ for sticking together.
Hemagglutination in Blood Typing
Erythrocytes, or red blood cells, can be categorized into ‘blood types’, such as A, B, and O.
Different people present different antigens on their cell surface, which are proteins to which antibodies bind. If a person is considered blood type A, then they have a protein present on their blood cells called A antigen. The same goes for type B, while type O is lacking both A and B antigens.In a laboratory, anti-sera, or serums containing antibodies, are used to determine a person’s blood type. These antibodies will bind explicitly to a certain antigen on the blood cell. When a specific anti-sera binds to their complementary blood type, hemagglutination occurs.
For blood transfusions, the process of hemagglutination is used to determine the right blood type to give a recipient.
Antibodies aren’t the only thing able to cause hemagglutination; viruses are also known to cause this development. Measles, mumps, and influenza (flu) viruses are common examples of viruses that can bind to red blood cells, collecting them together. This agglutination process is not the same as an antibody to antigen binding, and is distinctively called viral hemagglutination.
Viruses use hemagglutinin protein to attach to red blood cells and cause hemagglutination. Hemagglutinin is linked to the virulence of a virus, or how readily in can infect a host. A mutated hemagglutinin protein in the 1918-1920 ‘Spanish flu’ virus made for a historical deadly outbreak.A viral hemagglutination inhibition test is used in the laboratory to diagnose patients suffering from viruses that cause viral hemagglutination. This test takes advantage of antibodies that the patient’s body is making against a particular virus.
Red blood cells, the person’s serum (which may or may not contain antibodies against a particular virus), and the virus in question are all combined together.If the virus typically hemagglutinates red blood cells without any antibodies from the patient present, then clumping will occur. However, if a person is creating antibodies against the particular virus, these antibodies will bind the virus in a procedure called neutralization. Neutralization coats the virus with antibodies so that they cannot cause hemagglutination. If no hemagglutination occurs during the test, that person is positive for antibodies against that virus, and is likely suffering from that particular illness.
Agglutination occurs when cells are clumped together, just like wet sand sticking together to form a sand castle. Antibodies and viruses are like the water needed to hold the sand together: both able to cause the agglutination of red blood cells in a process called hemagglutination. Hemagglutination is used to determine a person’s blood type and utilizes antibodies found in anti-serum. Some viruses that contain hemagglutinin can bind to erythrocytes causing viral hemagglutination.
In the laboratory, a diagnosis of certain viral infections is determined using viral hemagglutination inhibition tests.