If a bacterium had a protein on its surface that humans also have, would it cause an autoimmune disease?

Question

Suppose that a bacterium happened to have a protein on its surface. This protein can also be found in the human body. If this bacterium were to then infect a human with an otherwise normal immune system, would his/her immune system attack the person's body, in addition to the bacterium?

The reason I'm asking this is because I have read a book about how, supposedly, the Soviet Union created a bacterium that did just that: they modified Yersinia Pestis to produce myelin which, supposedly, caused multiple sclerosis. The book's author claims that this really happened, but I am skeptical of that claim.

Answer 1

It's believed that many autoimmune cases are triggered by what you describe - pathogens or opportunist bacteria and viruses that contain proteins similar to human proteins.For example:

• Autoimmunity to hypocretin and molecular mimicry to flu in type 1 narcolepsy
• Translocation of a gut pathobiont drives autoimmunity in mice and humans
• Autoantigen cross-reactive environmental antigen can trigger multiple sclerosis-like disease

However, it's important to understand that although these cross-reacting proteins may be required in the process of autoimmunity, they aren't sufficient to cause autoimmunity alone (or else everyone would have autoimmunity all the time). Autoimmunity needs to have a whole bunch of steps, including several pieces of genetic susceptibility and environmental conditions, before the specific trigger will cause a problem (and it's likely that once the many other conditions are satisfied, there are multiple potential triggers that can set up the final cascade).