Anna Ruvinov - Immunology
Infectious microbes, such as viruses and bacteria, have limitless ways of evading human immunity. They can even turn the immune system against the rest of the body causing tissue destruction, a phenomenon known as autoimmunity. Many autoimmune conditions have an unknown cause or have been linked to specific genes and environmental factors. However, newer research is showing that many of these diseases with previously unknown etiologies may be due to an infectious agent.
One well-researched example is rheumatic fever (RF). This autoimmune attack on the heart occurs only after infection with Streptococcus pyogenes, a common cause of strep throat. S. pyogenes has several antigens targeted by the immune system, one of which is the infamous M protein. This antigen can resemble self-proteins found in human cardiac tissue, so antibodies produced by the immune system during an infection against this bacterial antigen can also bind in the heart and signal immune cells to attack. This process is called molecular mimicry, which allows S. pyogenes and other pathogens to indirectly damage our bodies.
Some other forms of autoimmunity may also involve molecular mimicry. For example, multiple sclerosis (MS) is a devastating disease in which the myelin sheath around neurons is destroyed by immune cells. Studies are now showing links between MS and Epstein-Barr Virus (EBV), a very common type of virus that infects a large population of humans. There are a few hypotheses describing how exactly EBV may contribute to MS development, one of which involves molecular mimicry. In one study done by Fujinami and Oldstone, it was shown that at least one EBV antigen induced a response in T cells isolated from MS patients. This alludes to the fact that the antibodies that activated those myelin-targeting T cells may be cross-reactive with EBV proteins. This cross-reaction is the key to establishing molecular mimicry and causing an autoimmune response.
Though it’s hard to wrap your mind around it, it’s become more apparent over the years that microbes have adapted to use our own body’s defenses against us.
References:
Tyler K. L. (2022). The enigmatic links between Epstein-Barr virus infection and multiple sclerosis. The Journal of clinical investigation, 132(9), e160468. https://doi.org/10.1172/JCI160468
Edited By: Firas Batrash, Editor-in-Chief
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