DA.F344(Cia5a) congenics had significantly reduced expression of genes previously implicated in RA pathogenesis, RA severity and articular damage, including Il1b, Il18, Mif, Mmp3 and Mmp14. These and other similarities between DA rats and RA synovial tissues’ gene expression, such as increased expression of chemokines, matrix proteins, adhesion molecules, mediators of innate immune responses, and others, underscore and further validate the potential clinical relevance of our model and discovery strategy. This evidence concerns the gene IL18 and rheumatoid arthritis.