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Tetramer: Definition, Analysis & Immunology

Instructor: Erika Steele

Erika has taught college Biology, Microbiology, and Environmental Science. She has a PhD in Science Education.

Have you ever wondered how doctors can detect viruses or even cancer by doing a blood test? Maybe, you've wondered how doctors can detect cancer before a person even has symptoms. This lesson will explain how tetramers are one of the many modern techniques used to detect the presence of a disease.

What is a Tetramer and Tetramer Analysis?

Have you ever wondered how doctors are able to detect cancer before a person even feels sick? If it isn't magic or psychic abilities, the obvious answer is modern medical technologies, but how do these procedures work? In this lesson, we will discuss tetramers and tetramer analysis.

Unfortunately, tetramer analysis doesn't have anything to do with Tetris. However, tetramer analysis, is a process that uses special proteins on the surface of our cells, called major histocompatibility complexes (MHCs), to detect T-lymphocytes, or T-cells, to determine whether or not a person has a disease. T-cells are a type of immune cell that go on search and destroy missions for diseased and cancerous cells. If they find one, they destroy it. If a T-cell is in a patient's body, it means they have the disease because their body is trying to fight it. Tetramer analysis will find the T-cell, and doctors can treat the patient for the disease before symptoms begin to show.

To begin understanding tetramer analysis better, let's first define a couple of terms starting with the word tetramer, which is easy to understand. You may know that 'tetra' means four, thus, tetramer is a large molecule made of four subunits. The next term, major histocompatibility complexes (MHCs), is a bit more complicated. As mentioned, it has something to do with tetramer analysis, but what are MHCs? Well, these proteins most certainly have nothing to do with Tetris, but they are vital in fighting disease and cancer.

Specifically, MHCs tell T-cells what's going on inside the cell they are attached to by showing bits of stuff that are inside the cells. When a T-cell sees the 'stuff' from inside the cell displayed in an MHC molecule, it will decide whether the cell is healthy or if the cell needs to be destroyed.

For instance, if a cell were infected with a virus, it would display pieces of that virus inside the MHC molecules on its surface. A T-cell would recognize that something is wrong with the cell, and the immune system would take steps to destroy the cell. One of these steps includes creating more T-cells that recognize the virus. Thus, when you get sick, you will have T-cells that indicate you are sick, and these T-cells can be detected in many ways including tetramer analysis.

Figure 1: T-cells are immune cells that recognize molecules displayed by MHC molecules found on the surface of our bodys cells.
tcell

What are the Parts of a MHC Tetramer?

MHC tetramers have four MHC molecules, but they also have other important components:

  1. Biotin, which is used to attach the four MHC molecules to beads coated with a protein called streptavidin.
  2. A peptide or antigen, which is a protein from a virus, bacteria, or cancerous cell bound to the MHC molecules. The peptide will bind to T-cells that would only be present if a person has the disease that you are trying to diagnose.
  3. A fluorochrome or a molecule that glows in fluorescent light to allow the tetramer to be detected.

Figure 2: A tetramer has 4 MHC molecules
tetramer

What Are the Steps of Tetramer Analysis?

Each T-cell has receptors that recognize specific antigens inside MHC molecules on cells. Tetramer analysis takes advantage of this interaction and allows scientists to detect diseases by mixing MHC tetramers with a sample containing T-cells from the patient. If a person has the disease or cancer, they will have T-cells that recognize unique antigens from a virus or bacterium that caused the disease or peptides from a certain type of cancer. For instance, if a person has leukemia, they will have T-cells that recognize peptides specific to leukemia. If a T-cell has bound to the MHC tetramer, it will be detected by measuring the amount of fluorescence. The steps are described in detail below:

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