Joint pain can exist without inflammation.
Rheumatoid arthritis autoimmune antibodies, which exist in joints before joint inflammation occurs, can cause pain by directly activating neurons in the pain system, independent of any inflammatory response. A new paradigm according to Swedish researchers.
Results that could facilitate the development of new non-inflammatory pain treatment modalities, focused on the activation of pain system neurons during rheumatoid arthritis or other autoimmune diseases.
Antibody
The researchers discovered that the antibodies involved in the autoimmune reaction form so-called immune complexes, which activate pain via direct stimulation of the Fc-gamma receptor, receptors found on neurons in the system pain. “We all know that inflammation is painful,” says Camilla Svensson, professor of physiology at the Karolinska Institute. “But the pain can appear before any sign of inflammation in the joints and can remain a problem after it heals. Our aim was to find the explanatory factors” for this process.
After injecting antibodies into the cartilage of mice, his team found that the animals became more sensitive to pain even before they could see any signs of inflammation in the joints. “The antibodies of these immune complexes can directly activate pain neurons” without joint inflammation, summarizes Camilla Svensson.
Immune complexes
Rheumatoid arthritis is a chronic inflammatory disease of the joints that progresses in flare-ups. It is an autoimmune disease, but several immunological, genetic, hormonal or environmental factors are necessary for it to trigger.
Without treatment, the disease gradually spreads to new joints and leads to the progressive deformation or destruction of the affected joints (often those of the hands and feet). In some rarer forms of the disease, extra-articular manifestations appear, affecting other organs. In France, rheumatoid arthritis affects 0.3 to 0.8% of the adult population, or about 200,000 people. It is two to three times more common in women than in men.
.