PECAM1 and systemic lupus erythematosus: To identify differences in the age-dependent differentiation pathway of RTE Tregs/Tresps via MN Tregs/Tresps or CD31+ memory Tregs/Tresp into CD31− memory Tregs/Tresps between healthy controls and SLE patients, we determined the percentages of RTE and MN Tregs/Tresps within the naive CD45RA+ Treg/Tresp pool with age and correlated these data with their proliferation capacity.