ICOS and systemic lupus erythematosus: We first assessed these cTFH cells (CD3+ CD4+ CXCR5+ ICOS+ PD-1+ cells) and cTFH2 cells (CCR6– CXCR3– TFH cells) in our SLE patient cohort (Supplementary Table 1) and confirmed both their increased representation among CD4+ T cells, an increased number of cTFH2 cells in active patients despite the SLE-related CD4+ T cell peripheral lymphopenia25, and a correlation between cTFH2 cell numbers and disease activity (Spearman r = 0.3682, P = 0.02, N = 37) unlike cTFH1 cell (CCR6– CXCR3+ TFH cells) and cTFH17 cell (CCR6+ CXCR3– TFH cells) proportions25,26 (Fig. 1a–f and Supplementary Fig. 1a–c).