Although the mechanisms responsible for the down-regulation of Egr2 expression in PD-1high MP CD4 T cells in RA are unknown, we have found that Egr2 expression in CD4 T cells is induced by TCR stimulation and suppressed by inflammatory cytokines such as IFNγ (Singh et al, 2017), suggesting that the inflammatory condition in patients may repress Egr2 expression in PD-1high MP CD4 T cells which is yet to be investigated. Here, CD4 is linked to rheumatoid arthritis.