ICOS and systemic lupus erythematosus: Additionally, the ratio of PD1+ICOS+cTfh1 cells in cTfh1 cells (but not PD1+ICOS+cTfh2 cells in cTfh2 cells and PD1+ICOS+cTfh17 cells in cTfh17 cells) was significantly higher in active patients than in HCs and inactive SLE patients (Figures 2G–I).