Where Does RA Start?
Written by Editor   
Wednesday, April 16, 2014 10:04 PM

A century and more ago, the "oral sepsis" hypothesis was a widely held explanation for chronic disease, suggesting that many common disorders -- including arthritis -- originated in periodontal infections.This practice fell out of favor eventually because of a complete lack of symptomatic relief, and was largely forgotten.  But today, with the concept of the microbiome as an integral contributor to health and disease, the oral cavity, along with other mucosal sites, has once again become a source of attention among researchers.

Considerable evidence has now accrued implicating the periodontium, although debate continues.

A group of researchers at the University of Colorado have raised the additional possibility of the lung as another possible site for RA disease initiation.  "The lungs made a lot of sense to us. A lot of stuff from the environment comes in to the lung where the immune system has to deal with it. We know that mucosal surfaces have the immune machinery present to be able to mount immune responses, and it's not a big step to think that could go bad and cause autoimmunity."

As to the key uncertainty of how infection in the gums or antibody generation in the lungs could lead to disease manifestations in the joint.  "This is the million dollar question, which I don't think anyone can answer at this point."  Inflammation itself also may contribute to the process.  "It could be that inflammation from bacteria causes changes in our own tissue, which then becomes a target for the immune system." In addition, the immune response can evolve over time, shifting from one target tissue to another.

"We also know that immune cells and proteins move around in the body, and the joints are particularly susceptible to things that flow through the blood and pile up. That's why when you get the flu you can have aches and pains in your joints, because of immune debris building up."

An additional site that has been proposed is the gut, where an alteration of commensal bacteria has been identified in patients with RA.

"I think different people might have different sites, with some having the gums, others the lungs, and still others the gut mucosa," more translational and clinical research will be needed to fully understand the relationship between the microbiome and autoimmunity.

Source:  http://www.medpagetoday.com/Rheumatology/Arthritis/45289