Since Tfh cells are characterized by a variable expression of PD-1, we also evaluated the presence of PD-1 on circulating follicular CD4+CD45RA−CXCR5+ and non-follicular CD4+CD45RA−CXCR5− T cells from CVID patients and controls (Figure 2A). This evidence concerns the gene CD4 and common variable immunodeficiency.