PECAM1 and myeloid sarcoma: Comparative studies on treated versus untreated MS patients have sought to determine effects of different treatment strategies on numbers of TRECs and/or CD31+ RTE cells in peripheral blood mononuclear cells (PBMC) and in the CD4+ or CD8+ T cell compartments specifically (Fig. 5) [154, 156, 159–161, 217, 218].