FAP and rheumatoid arthritis: More recently, fibroblast subsets defined by Thy-1 have been further refined, particularly in the synovium where Thy-1 status along with the markers CD34 and cadherin 11 define lining and sublining synovial fibroblasts in human rheumatoid arthritis (11), while Thy-1 and FAP mark subsets of inflammatory and destructive phenotypes in murine arthritis (10).