PECAM1 and systemic lupus erythematosus: To further detect differences in the age-dependent differentiation between healthy volunteers and SLE patients, we examined the imminent differentiation of RTE Tregs/Tresps via MN Tregs/Tresps into CD31− memory Tregs/Tresps, as well as the differentiation of resting naive MN Tregs/Tresps into CD31− memory Tregs/Tresps.