CD4 and systemic lupus erythematosus: This observation was consistent with our previous findings using this same technology on an independent IFNhi SLE patient11, and further supports that the presence of a rare subset of CD4+ CTLs in blood, marked by the co-expression of surface markers usually expressed on cytotoxic CD8+ T cells, including CD57, CX3CR1 and KLRG1, is a feature of SLE patients with active disease.