CD4 and common variable immunodeficiency: Most of these insights are confirmed in the original study of Bogaert et al. (9) where they also noticed a general decrease of switched memory B cell populations, a decrease of switched memory B cells that express IgG and an increase of CD21low B cells in CVID patients, a decrease in CD4+ naïve T cells and a decrease in NK cells in CVID patients and in patients with other PADs.