Figure 5: Possible explanation of B cell maturation defect in patients with CVID. The number of naïve B cells is similar in patients and controls. Since the number of IgM+ IgD− CD23− CD27− B cells is higher and that of IgM− IgD− CD23− CD27− is lower in patients compared to controls, we can hypothesize that the defect in B cell maturation lies at this step of B cell maturation.