The pathogenesis of rheumatoid arthritis.

Rheumatoid arthritis (RA) is due to a combination of phagocytosis and anaphylaxis gone awry. Immune complexes create their havoc via Fc gamma III receptors that signal via the tyrosine phosphorylation immunoreceptor pathway. Anaphylatoxins, mainly C5a, signal via the MEK kinase cascade, and both engage in cross-talk via NF kappa B. Aspirin-III blocks signals sent by both: immune complexes via FCR, and anaphylatoxin via C5 receptors. Drugs that affect both pathways, for example anti-B cell monoclonal antibodies, such as rituximab, and anti-C5 monoclonal antibodies, such as pexelizumab are currently being investigated. We now appreciate that cytokines are important mediators of inflammation in RA but are downstream of the primary insults: immune complexes and anaphylatoxins. We can therefore begin to ask what the antigen or antigens might be that produce IgGs reactive to 7 S or 19 S rheumatoid factors. The primary antigens of RA could well be CPs, formed perhaps by oral bacteria. Once immunoglobulins become recognized by rheumatoid factors, immune complexes form, and these activate anaphylatoxins. Phagocytosis and anaphylaxis are the proximal events of RA.