“What’s more, the height of the coating index to E. coli correlated with the BASDAI score in terms of the arthritis being more severe,” he said. Fifteen E. coli isolates from three patients were an invasive-adherent strain of the bacterium. Typically, commensal E. coli strains are neither adherent nor invasive. “Attachment and invasion of the organism to intestinal mucosa explains why the organism would activate Th17 responses.”
These authors conducted a study of KBxN mice and found that anti-GPI antibody titers were similar when the mice were inoculated with SFB or with the invasive-adherent E. coli strain isolated from the patients in the study. “This mouse is engineered to have autoantibody responses to GPI, but an organism implicated in human Crohn’s SpA, an invasive-adherent E. coli strain, was sufficient to cause Th17 responses and autoimmune arthritis in this model system,” Dr. Steere said.
Periodontitis & Autoimmunity
An epidemiological association exists between periodontitis and RA, and periodontal disease offers lessons on why RA patients may have autoantibody responses to citrullinated proteins, said Dr. Steere.