CD40LG and common variable immunodeficiency: This suggests that the CD21low B cells in these patients are distinct from CD21low B cells reported in CVID patients (Isnardi et al., 2010; Rakhmanov et al., 2009), further implying a unique intrinsic B cell defect (involving all major immunoglobulin isotypes, including IgM) linked to AIOLOS N160S.