The frequency of CD4+CXCR5+ T cells was significantly increased in HT patients compared with healthy controls (P = 0.0092) (Figure 1(b)), whereas the frequencies of CD4+CXCR5+PD-1+ and CD4+CXCR5+ICOShigh Tfh cells were comparable among these groups (Figures 1(c) and 1(d)). Here, PDCD1 is linked to hematocrit.