Genetic dissection of a rat model for rheumatoid arthritis: significant gender influences on autosomal modifier loci

Rheumatoid arthritis (RA) is a common, chronic, autoimmune, inflammatory di sease that is influenced by genetic factors including gender. Many studies suggest that the genetic risk for RA is determined by the MHC, in particula r class II alleles with a 'shared epitope' (SE), and multiple non-MHC loci. Other studies indicate that RA and other autoimmune diseases, in particula r insulin-dependent diabetes mellitus (IDDM) and autoimmune thyroid disease (ATD), share genetic risk factors. Rat collagen-induced arthritis (CIA) is an experimental model with many features that resemble RA. The spontaneous diabetes-resistant bio-breeding rat, BB(DR), is of interest because it is susceptible to experimentally induced CIA, IDDM and ATD, and it has an SE i n its MHC class II allele. To explore the genetics of CIA, including potent ial gender influences and the genetic relationships between CIA and other a utoimmune diseases, we conducted a genome-wide scan for CIA regulatory loci in the F-2 progeny of BB(DR) and CIA-resistant BN rats. We identified 10 q uantitative trait loci (QTLs), including 5 new ones (Cia15, Cia16*, Cia17, Cia18* and Cia19 on chromosomes 9, 10, 18 and two on the X chromosome, resp ectively), that regulated CIA severity. We also identified four QTLs, inclu ding two new ones (Ciaa4* and Ciaa5* on chromosomes 4 and 5, respectively), that regulated autoantibody titer to rat type II collagen. Many of these l oci appeared to be gender influenced, and most co-localized with several ot her autoimmune trait loci. Our data support the view that multiple autoimmu ne diseases may share genetic risk factors, and suggest that many of these loci are gender influenced.