The link between Proteus mirabilis, environmental factors and autoantibodies in rheumatoid arthritis

Rheumatoid arthritis (RA) is a relatively common and potentially disabling immune-mediated inflammatory systemic disease, predominantly affecting women and characterised by multiple small joint arthritis. Extensive data supports the roles of genetic, environmental and microbial factors in the triggering and development of this disease. Proteus mirabilis is considered as the main microbial culprit in the causation of RA. The evidence for the role of these microbes in RA and their links with commonly associated autoantibodies such as rheumatoid factors and anti-citrullinated peptide antibodies have been elucidated together with their relations with some of the non-microbial environmental factors which have been implicated in the aetiopathogenesis of RA. The most likely mechanism in the development of RA is "molecular mimicry" where Proteus antigens were found to share homologous sequences, which cross-react with certain self-antigens present in synovial tissues. This could raise possibilities for implementing a new therapeutic strategy in the treatment of RA.