TFRC and rheumatoid arthritis: Clinical studies have investigated Tfr and Tfh cells in multiple autoimmune diseases and have found a decreased frequency of circulating Tfr cells and an increased Tfh frequency as well as an aberrant Tfh/Tfr ratio in rheumatoid arthritis (RA) (15), systemic lupus erythematosus (SLE) (16) and myasthenia gravis (17).