Rheumatoid Arthritis is suspected to be caused by pathogens like bacterias or viruses. You're already hosting these bacteria and/or viruses. While some will invade you from outside passing through your gut.
There're many ranges of mechanisms by which pathogens cause disease!
All pathogens, for their survival, will require that they colonize you. They'll find an appropriate hiding place in your body. They'll avoid being detected by the immune system. Some pathogens, after eating you up, (just kidding) will exit to spread to another person.
Our bodies are tightly protected from the outside world, by our thick and tough skin. But our inside tissues like eyes, nasal passage, lungs, Gut etc are, however, have only one layer of epithelial cells( cells arranged in one or more layers that form as a barrier between our bodies and outside environment).
How do they escape from your Immune system?
Some pathogens infect their host without entering the cell,
Viruses and some Bacterias, however, bind to normal human cells, making it impossible for an immune system to detect them as foreign.
They use cell's cytoskeleton(a network of filaments) to move around in your body.
Viruses take over the metabolism of your cell.
Pathogens can change the way your body behaves to facilitate their spread.
Some will hide far way deeper in some of your organs, where they lay dormant for decades. They reactivate, spread and migrate to other organs when your immune system is weak!
Certain invaders, such as Mycoplasma and some other bacteria will resemble your own molecules (molecular mimicry). this will help them hide from your immune system which will result in autoimmune response towards the agent that's being mimicked.
Other viruses and bacteria will kill your cells. This will result
Bacterias such as Streptocoques, Staphylocoques, and Yersinia are even much clever. They carry superantigens( proteins) that can activate your immune, therefore, creating an autoimmune disorder.
Which Viruses and Bacterias cause Rheumatoid Arthritis?
Epstein-Barr virus, Rubella virus, Porphyromonas gingivalis, Proteus mirabilis, Mycoplasma(smallest bacteria), etc..
Gastrointestinal infections with bacteria like Salmonella, Shigella, Yersinia, Campylobacter etc.. may cause inflammation in the joints.
Patients who show evidence of nodules in the joints are frequently those who have a history of bacteria Streptococcal infections. Even if the infection occurred in childhood.
People with diseases like Lyme or Fibromyalgia, and they test positive for Mycoplasma or Chlamydia do show signs and symptoms of Rheumatoid Arthritis.
And now that you know,
In Rheumatoid Arthritis, inflammation is actually your body's natural defense against an infection in connective tissues. This struggle results in pain and to some point disfiguring because the pathogen is binding to your cell.
Feed your body with nutritious food. That can help to starve and eliminate pathogens. Don't hate your body because you've been sold that it's attacking itself.
Resources: NCBI https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4131749/ rheumatic.org http://rheumatic.org/. Dr.Katherine M. Poehlmann PhD book; Rheumatoid Arthritis. Dr. Jean Seignalet's book; L'alimentation ou la troisième médicine..... and many other sources