MKI67 and systemic lupus erythematosus: The Ki67 staining of the different Treg/Tresp cell subsets revealed a significant age-independent reduction in CD31+ and CD31− memory Treg proliferation, suggesting a predominant differentiation via CD31+ memory Tregs in SLE patients, which most probably is strongly restrained by the immunosuppressive drugs, even below the normal level of healthy volunteers.