TNF and rheumatoid arthritis: PBMCs from RA patients showed markedly higher frequencies of SIGIRR+ memory CD4 T cells secreting TNF-α than those from healthy individuals (median 39.4% vs 18.6%, Additional file 3: Figure S3 A-B) and a slight increase in IL-17-producing cells (median 0.83% vs 0.63%, Additional file 3: Figure S3 A-B).