CD28 and systemic lupus erythematosus: We identified two CD4+ TEM which were present in higher percentages in SLE: CD38 negative (MC08: CD45RA−CD4+CD27+CD28+CD38−CD127−CD197−) and CD38 positive (MC11: CD45RA−CD4+CD27−CD28+CD38+CD127−CD197−), differentiating SLE from therapy-naive RA and SSc.