ICOS and systemic lupus erythematosus: This may explain the decreasing percentages of Ki67+ cells within all ICOS+ Tresp subsets except RTE Tresps (Fig. 2B), confirming a strong suppression of the age-dependent differentiation in female SLE remission patients, as well as the age-independently increased percentages of ICOS+ Tresps within the total CD4+ T helper cell pool (Fig. 1C).