The frequency, function, and properties of various subsets of Tregs including natural Tregs (nTregs), IL-10-producing type 1 Tregs (Tr1 cells), TGF-β-producing Th3 cells, CD8+ Tregs, and NKT regulatory cells have been investigated in various studies associated with RA and collagen-induced arthritis (CIA) as experimental model of this disease. This evidence concerns the gene TGFB1 and rheumatoid arthritis.