Pr Krock and collaborators previously found IgG antibodies from fibromyalgia patients induce pain-like behavior in mice. Another important actor are the glia cells, which cover and protect the neurons. These antibodies bind human and mouse satellite glia cells (SGCs), suggesting that antibodies and autoimmunity could underlie a subset of fibromyalgia. However, the initial study did not investigate the frequency with which fibromyalgia patients have antibodies. While researchers have not yet identified specific antigenic targets of the antibodies, we do know that they bind to SGCs. Thus, the research team aimed to determine how often fibromyalgia patients have antibodies against SGCs, and whether they are associated with disease severity.<\/p>\n\n\n\n
Researchers developed an in vitro cell based assay, where they studied cells in laboratory as opposed to directly on humans or animals. Mouse cells from the dorsal root ganglia (DRG) called SGCs were used to semi-quantify serum and plasma levels of anti-SGC IgG antibodies. The research team measured the levels of anti-SGC antibodies from fibromyalgia patients and controls in cohorts from the Karolinska Institute (Stockholm, Sweden) and McGill University and assessed how anti-SGC antibody levels associated with pain and fibromyalgia questionnaire as well as quantitative sensory testing. In other words, how are autoantibody levels related to the self-reported questionnaires and pain testing? To confirm the findings from mouse cell culture studies, a complementary technique was developed to measure the levels of anti-SGC antibodies that bind to human DRG tissue.<\/p>\n\n\n\n
On average, individuals with fibromyalgia have higher levels of anti-SGC antibodies. Furthermore, the levels of anti-SGC antibodies were positively correlated with pain assessed by self-reported scales. In this case, patients were asked to complete the Visual Analogue Scale and indicate the level of pain on a continuous line between two end point. Another scale that was used was the Numeric Pain Rating Scale, where patients had to rate the level of pain. The levels of antibodies were also positively correlated with fibromyalgia impact questionnaire scores, meaning that individuals with higher levels of anti-SGC antibodies more often had more severe pain symptoms. Furthermore, antibody levels correlated with pressure pain thresholds. When the fibromyalgia patients were divided into severe and mild pain groups, only the severe group had elevated anti-SGC antibodies compared to control subjects. The research team was able to confirm their findings from mouse SGC cultures with human DRG tissue and found the fibromyalgia serum had higher levels of antibodies against human SGCs, specifically those patients with more pain.<\/p>\n\n\n\n
A subset of fibromyalgia patients has elevated antibodies against satellite glia cells, specifically those with more severe pain. These findings set the foundation for future studies aiming to develop autoantibody-based diagnostic testing to identify patients for immunomodulatory treatments that target autoantibody production and turn over.<\/p>\n\n\n\n