PECAM1 and systemic lupus erythematosus: Beside these differences concerning the age-dependent differentiation of RTE Tregs/Tresps between healthy controls and SLE patients, our data also reveal that there may be a general age-independent increased differentiation of RTE Tregs/Tresps via CD31+ memory Tregs/Tresps into CD31− memory Tregs/Tresps in SLE patients compared with healthy controls (Fig. 9c, d).