Diarrheic episodes caused by the foodborne pathogens Campylobacter, Salmonella, Shigella or Yersinia may lead to a sterile arthritis such as reactive arthritis, Reiter's syndrome or ankylosing spondylitis. Reiter's syndrome and reactive arthritis have been shown to be sequelae in a few well-studied bacterial food poisoning outbreaks. Reactive arthritis, Reiter's syndrome and ankylosing spondylitis show strong familial association related to the gene for HLA-B27 (HLA = human leucocyte antigen) antigen. Why HLA-B27-positive individuals are more susceptible to arthritis is not known, but molecular mimicry between the HLA-B27 antigen and antigens of triggering bacteria has been demonstrated and this mimicry has been proposed as a mechanism involved in etiology of the arthritides. Antigens from bacteria that triggered the arthritis are present in arthritic joints but bacterial cells are not found. Antibodies and T-cells specific for the triggering bacteria have been demonstrated in arthritic patients. T-cells present in synovial joints respond specifically to the particular arthritic triggering pathogen. The cells that respond to bacterial antigens belong to the T-cell subset TH1 that secrete a limited number of cytokines but it is not known if cytokines are involved in arthritis. A few studies have demonstrated that T-cells from the joints of arthritic patients respond to both bacterial and human heat shock proteins indicating that autoimmunity may be involved in causation of arthritis. While only about 2% of a population exposed to a triggering infection will acquire arthritis, these individuals undergo pain and suffering as well as economic hardships as a result of their disease.
Serum antibodies from patients with ankylosing spondylitis and Reiter's syndrome are reactive with HLA-B27 cells transfected with the Mycobacterium tuberculosis hsp60 gene.
