Your immune system is like a very well-organized and effective military force. The task of the Armed Forces and other branches of the military is to defend and protect the people within its country against real or potential threats. The role of the immune system is much the same, to defend and protect the person against real or potential threats. These threats are often infectious organisms such as bacteria, viruses, fungi, or parasites, and other intruders. These intruders may include environmental toxins, chemicals, and even food proteins as well.
Other threats can come from within the body itself, such as in the case of the development of cancer cells where the immune system must identify it as ‘foreign’ and ‘dangerous’ and attack it, ultimately destroying it in a process called apoptosis.
Just as the military is complex and involves many different branches with different roles, each undergoing specific, intensive training to identify and get rid of the enemy, our immune system is incredibly complex, involving many different parts, all with the ability to identify and destroy the ‘enemy.’
So what happens when there is ‘friendly fire’ within the military? Friendly fire is an attack by a military force on its own soldiers or soldiers of an allied force.
How does this happen? Friendly fire arises from the confusion that is inherent in warfare. An attack may be aimed at what is thought to be an enemy force but may accidentally end up hitting one’s own. Sometimes there is a mistaken identity where the troops attack their own believing they are attacking their enemy. These errors are more likely to occur under times of significant stress, including the fear, uncertainty, and chaos that accompany war.
In order to avoid friendly fire, modern armies earnestly seek out ways to reduce this tragedy. They improve their training and communication and use more sophisticated electronic devices.
Just like the military, our immune system can occasionally ‘get it wrong’ and ‘friendly fire’ occurs. In medicine, this is known as an autoimmune process where the body attacks itself. This is thought to be the result of molecular mimicry.
Your body’s immune system is designed (‘trained’) to recognize an invader and memorize its structure. It does this by identifying a part of a protein. Proteins are made up of strings of amino acids. Your immune system identifies a particular string of amino acids in a ‘foreign invader’ and triggers an immune response so that the body doesn’t get overwhelmed and die as a result of this attack.
In molecular mimicry, a string of amino acids found in the invader is very similar in structure to proteins found within the body. Because your immune system scours the body looking for this sequence of amino acids in order to make sure that no ‘enemies’ got through their barrier, it finds the amino acid sequence in tissues within the body and the friendly fire (autoimmune) attack begins.
Since 70% of your entire body’s immune system lines your GI tract, the ‘army’ is waiting for invaders to penetrate the intestinal wall. This is where proteins from foods we eat may get through our leaky gut and trigger the immune response.
For example, the amino acid sequences found in gluten are similar to particular tissues in the body, including the thyroid, joints, and pancreas. Molecular mimicry (friendly fire) is the proposed reason for the autoimmune diseases of the thyroid (Grave’s and Hashimoto’s), joints (Rheumatoid arthritis), and pancreas (Type-1 diabetes) seen in those with intestinal permeability who consume gluten.
There are 3 main types of proteins that are important in the development of autoimmune disease:
1. Self-proteins are human body proteins. Myelin proteins in myelin sheaths in the nervous system would be such a protein. Multiple Sclerosis is an autoimmune disease where the body attacks these myelin proteins.
2. Infections such as viruses, bacteria, fungi
3. Food proteins. There are over 400 different proteins in cow’s milk and most have over 150 amino acids.
Molecular mimicry is thought to be at the root of many autoimmune diseases.
In children, Strep bacteria has been identified as the cause of an autoimmune condition called PANDAS (Pediatric Autoimmune Neuropsychiatric Disorders Associated with Strep infections),
Strep is an ancient organism that survives death by its human host’s immune system by hiding from it as long as possible. It does this by putting molecules (the sequence of amino acids) on its cell wall that look nearly identical to molecules found on the child’s heart, joints, skin, and brain tissues. This is “molecular mimicry” and allows the Strep to evade detection for a time.
Over time the molecules on the strep bacteria are eventually recognized as foreign and the child’s immune system reacts to them by producing antibodies. Because of the molecular mimicry, the antibodies react not only with the strep molecules but also with the human host molecules that were mimicked.
The cross-reactive antibodies then trigger an immune reaction that “attacks” the mimicked molecules in the child’s own tissues. In the case of PANDAS, an area of the brain known as the basal ganglia is involved resulting in the abrupt onset of neurologic and/or psychiatric complaints.
Here is a table of examples of human autoimmune diseases with possible molecular mimicry as a mechanism.
Just as our modern armies seek ways to avoid friendly fire, we need to improve our immune system’s communication techniques and boost our health to avoid and treat autoimmune disease.
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