| Abstract
| - OBJECTIVE. To investigate linkage of candidate disease susceptibility genes to rheumatoid arthritis (RA) in affected sibling pair families stratified for specific clinical features. METHOD. Two hundred RA affected sibling pair families were genotyped for informative microsatellite markers mapping within or less than 3cM from: INFα, INFγ, INFβ, IL1α, IL1β, IL1R, IL2, IL6, IL5R, IL8R, BCL2, CD40L, NOS3, NRAMP, α1anti-trypsin, and α1 anti-chymotrypsin, using fluorescence based automated technology. Linkage was examined by defining allele sharing sibling pairs. This was assessed by maximum likelihood—inheritance by descent methods. RESULTS. An increase in allele sharing was seen for IL5R in female sibling pairs (LOD 0.91, p = 0.03), for INFγ in sibling pairs with an affected male (LOD 0.96, p = 0.03) and most significantly for IL2 in sibling pairs where one or both were persistently seronegative (LOD 1.05, p = 0.02). CONCLUSION. Weak evidence of linkage of RA to IL5R, IFNγ, and IL2 has been detected in clinical subsets of sibling pairs suggesting that RA is a genetically heterogeneous disease.
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