IL17A and rheumatoid arthritis: Addition of tocilizumab (IL-6R blockade) or abatacept (CTLA4-Ig, which blocks CD80/CD86-mediated co-stimulation), both of which are biologic drugs routinely used in the clinic to treat rheumatoid arthritis, did not increase IL-10+ frequencies in CD4+ T cells, IL-17+, IFNγ+, or TNFα+ CD4+ T cell subpopulations (Figure 4B).