PECAM1 and systemic lupus erythematosus: To show differences in the differentiation of ICOS+- and ICOS−-Tregs/Tresps between healthy volunteers (Group 1) and SLE patients in remission (Group 2) or SLE patients with a flare of the disease (Group 3), we determined the composition of the total CD4+-ICOS+- and ICOS−-Treg/Tresp pools with RTE-, MN-, CD31+- and CD31−-memory-cells in both healthy and affected individuals of different ages (Figure 1A,B,E,F).