CD28 and rheumatoid arthritis: In another study, the authors demonstrated that genes located near RA‐associated variants were highly expressed in CD4+ effector memory T cells.58 Following this observation, Hu et al. 59 isolated CD4+ T effector memory cells and measured relative cell abundance, as well as gene expression of 215 genes located in RA loci, and cell proliferation capacity upon in vitro stimulation with anti‐CD28/anti‐CD3.