TNF and rheumatoid arthritis: Indeed, a study attempting to predict synovial gene expression by analyzing serum metabolic profiles of patients with RA on methotrexate concluded that serine/glycine/phenylalanine metabolism and the biosynthesis of aminoacyl-tRNAs were related to TNF-α/CD3E and B-cell/plasma signatures (13), pointing to the involvement of these pathways in the regulation of lymphocytes in the rheumatoid synovium.