CD4 and rheumatoid arthritis: Decreased plasma levels of TGFBR2 correlated with diminished TGFBR2 expression in the CD123 + HLA-DR−, CD4+ and CD14+ cell populations from the AR group; CD16+ and CD4+ cells from the AS group; CD16+ and CD4+, CD14+, and CD19+ cells from the AR + AS group; and CD4+ cells from the RA group (Fig. 5b).