AbstractObjectiveTo identify disease‐specific gene expression profiles in patients with rheumatoid arthritis (RA), using complementary DNA (cDNA) microarray analyses on lymphoblastoid B cell lines (LCLs) derived from RA‐discordant monozygotic (MZ) twins.MethodsThe cDNA was prepared from LCLs derived from the peripheral blood of 11 pairs of RA‐discordant MZ twins. The RA twin cDNA was labeled with cy5 fluorescent dye, and the cDNA of the healthy co‐twin was labeled with cy3. To determine relative expression profiles, cDNA from each twin pair was combined and hybridized on 20,000‐element microarray chips. Immunohistochemistry and real‐time polymerase chain reaction were used to detect the expression of selected gene products in synovial tissue from patients with RA compared with patients with osteoarthritis and normal healthy controls.ResultsIn RA twin LCLs compared with healthy co‐twin LCLs, 1,163 transcripts were significantly differentially expressed. Of these, 747 were overexpressed and 416 were underexpressed. Gene ontology analysis revealed many genes known to play a role in apoptosis, angiogenesis, proteolysis, and signaling. The 3 most significantly overexpressed genes were laeverin (a novel enzyme with sequence homology to CD13), 11β‐hydroxysteroid dehydrogenase type 2 (a steroid pathway enzyme), and cysteine‐rich, angiogenic inducer 61 (a known angiogenic factor). The products of these genes, heretofore uncharacterized in RA, were all abundantly expressed in RA synovial tissues.ConclusionMicroarray cDNA analysis of peripheral blood–derived LCLs from well‐controlled patient populations is a useful tool to detect RA‐relevant genes and could help in identifying novel therapeutic targets.