TNFRSF18 and Autoimmunity: Because circulating activated T cells are found in autoimmune disorders, and CD25 and GITR are also markers of activated effector T cells [27,40-42], we performed a phenotypic characterization of CD4+CD25low/-GITR+ and CD4+CD25highGITR− cells in SLE patients to verify whether they showed a Treg or activated phenotype.