What Proteins Are Fundamental to the Immune System?

Your immune system consists of a vast array of proteins, cells and organs that work together to help keep your body safe from invasion by pathogens. Pathogens are simply disease-causing organisms, such as infectious bacteria and viruses. There are a number of proteins that the immune system depends upon in order to maintain normal function.


IgG Antibodies

Of all the immune system proteins, IgG antibodies are the best known in the general population. These are antibodies that circulate in your bloodstream and provide the bulk of your defense against invading bacteria and viruses. They do this in more than one way, explains physiologist Lauralee Sherwood, Ph.D. They can, for instance, clump pathogens together, making their removal from your bloodstream easier. They can also mark pathogens for destruction. Because they can cross the placenta, IgG antibodies can also provide newborns with short-term immunity until they start building their own immune system.

Other Antibodies

There are several other classes of antibodies, all of which are important for normal immune function. IgA, for instance, lines the viscous membranes of your digestive tract and can help defend your body against ingested pathogens. Babies get this type of antibody from breast milk. This is one of the reasons why breastfeeding helps protect infants from disease. IgE, on the other hand, mainly protects against parasites, such as worms. IgM plays important roles in early immunity and initial exposure to a pathogen, before you've had time to produce IgG.


The MHCs, or major histocompatibility complexes, are another group of proteins that are critical to immune system function. These are proteins that your cells make and express onto their cell surface. They allow your immune system to monitor what's going on inside the cell and provide an early detection system in case of an invasion by a pathogen. Other immune system components regularly check the MHCs on cell surfaces in order to monitor cell health.


T-cells are white blood cells that actively participate in the immune response whenever your body is attacked. They often have cell surface receptors --also known as co-receptors--that help them recognize and take up pathogens. A T-cell coreceptor called CD3 receptor is an important immune system protein that also appears to have a role in brain development, according to ScienceDaily.com. In addition to helping the immune system monitor your body for invading pathogens, CD3 also seems to monitor the brain for incorrect connections between neurons, which helps the brain function more efficiently.


This article reflects the views of the writer and does not necessarily reflect the views of Jillian Michaels or JillianMichaels.com.