We previously reported impaired but still detectable Ig secretion in purified B cell cultures stimulated with anti-CD40 or TLR-9 ligand in 15 CVID patients irrespective of IL-21 influence43, and Borte et al. demonstrated that IL-21 restores Ig production by PBMCs in 14 CVID patients34. Here, CD40 is linked to common variable immunodeficiency.