Autoimmune Disease and RA
Understanding the role played by the body’s immune system in the progress of rheumatoid arthritis.
What Causes Rheumatoid Arthritis?
Recent research is uncovering a complex interplay between the hormonal, nervous, and immune systems in rheumatoid arthritis. Researchers are also trying to learn why rheumatoid arthritis often improves during pregnancy. One study suggests that certain proteins passed between the mother and unborn child may be responsible for the improvement. These are proteins that help the immune system tell the difference between the body’s own cells and foreign ones. This exchange of proteins may change the mother’s immune system during pregnancy in some way.
Both genetics and environmental factors combined appear to be the main triggers of RA.
Genetics. Those at risk for autoimmune diseases such as rheumatoid arthritis inherit certain types of human leukocyte antigens (HLAs). These are white blood cell proteins that cause the white blood cells to overreact. This genetic difference puts related family members at an increased risk for one or more autoimmune diseases.
Researchers are collecting information from families to gain even greater insights into genetic links. They have identified several genetic regions that increase the susceptibility for rheumatoid arthritis in animal models. Recent studies have found several novel genes associated with the disease.
Environmental factors. An original insult from an infection or other factor in the environment can lead to chronic arthritis years later. This makes it more difficult to identify the culprit. However, researchers are homing in on some possible targets, Peyman tells WebMD. They include:
- Parvovirus B19, also known as fifth disease
- Epstein-Barr virus, a prominent infectious agent
- Bacterial gum disease (periodontitis)
“Recent studies show that smoking tobacco modifies proteins in the lungs,” says Peyman. “These modified proteins are similar to those showing up in inflamed joints.” Cells travel from the lungs to an injured joint, where the immune system reacts strongly, causing ongoing inflammation.”
A similar process can happen with an infection. In people with genetic susceptibility, a minor localized infection in the mouth, for example, can trick the immune system into looking other places for modified proteins. This can lead to a “smoldering additional inflammation” in the body, which chronically attacks the joints, Peyman says.
“This molecular mimicry is the basis of much of the research into the immunology of autoimmune disease,” Peyman says. “Researchers are trying to find which components of a microbe or environmental insult are similar to the known targets of the immune system in autoimmune diseases. With rheumatoid arthritis, this has been a decades-long quest.”