STAT1 and rheumatoid arthritis: IFNα activation of STAT1 was significantly lower (p < 0.01) in RA than HC (Cohort 1) in the following six subsets: total monocytes, total B cells, naïve helper Th cells (CD4+CD45RA+), memory/effector Th cells (CD4+CD45RA-), naïve Tc cells (CD4-CD45RA+), and memory/effector cytotoxic Tc cells (CD4-CD45RA-) (Fig 1B and 1C).