U.C.L.A. Rheumatology Pathophysiology of Disease Course Lecture,
Second Year Medical School 1997

  
 
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Rheumatoid Arthritis     Page 15
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      B cells are provoked to produce an antibody called Rheumatoid Factor (RF) which is typically an IgM antibody directed against the Fc portion of IgG. RF binds avidly to IgG and it can be detected in the patients' sera by reacting them with IgG-coated latex particles. IgG rheumatoid factors may also be produced which are IgG molecules acting as antibodies against other IgG molecules. IgG RFs may self-associate into immune complexes. They are less frequently present and more difficult to detect in the serum than IgM RFs but they may be more likely to cause tissue damage.Immune complexes are produced in the synovium and released into the joint cavity. They activate complement, attract PMNs to the site and cause a sustained inflammatory response.
       It is estimated that more than a billion PMNs enter a moderately inflamed rheumatoid knee joint each day and they release proteinases which degrade articular cartilage, menisci and ligaments. T cells stimulate the synovium to grow and the proliferating synovium destroys the cartilage and the underlying subchondral bone (figure 6). Macrophages and fibroblasts also participate in the pathogenic processes.
      Only diarthrodial joints are lined by synovium, so these are the major targets of RA. The axial skeleton which lacks diarthrodial joints is not principally affected in RA whereas the small and large peripheral joints which are all lined by synovium become severely		    
 
Figure 6. A foot xray from a 25 year old women with RA clearly shows erosive bone damage. Click thumbnail figure to view full graphic. jpeg 219 x 164 pixels 6kbs photo CAC
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