CD4 and rheumatoid arthritis: Intriguingly, the CD25 did not increase in MAIT cells from early, untreated RA patients, suggesting that either RA MAIT cells or CD4+ MAIT cells react poorly to E. coli ligand (median control MFI = 177, SpA MFI = 95.2, RA MFI = 0; p = 0.0004, controls vs RA p = 0.0005, SpA vs RA p = 0.0110).