Immunogenetics of rheumatoid arthritis.

There is overwhelming evidence that Rheumatoid Arthritis (RA) is under genetic influence, but the mechanisms are unclear. Many studies have implicated HLA-DRA as an important marker for disease susceptibility, though this is not the case in all racial groups. Analysis of familial RA has shown a marked restriction in allelic combinations or supratypes. Mapping of the MHC by complement allotyping has further emphasised the relatively limited number of supratypes associated with RA. Disease associated supratypes may also serve as markers for complications induced by drugs such as D-penicillamine, and be shared by other diseases such as Type I Diabetes. That supratypes may have important biological functions is drawn from studies in complement C2 deficiency and 21-hydroxylase deficiency. Examination of supratypes should allow a more direct approach in understanding the pathogenetic mechanisms in RA, and the role of other markers outside the MHC.