Stimulation with CD1d tetramer and α-galcer, a natural ligand for iNKT, also failed to adequately expand the iNKT population.54 The combined reduction in both Treg and iNKT highlighted a potential problem with thymic output, as both are considered as primary products of the thymus.55–57 In keeping with this, immunophenotypic data often reveal lower frequencies of naïve (CD45RA+CCR7+) CD4 and CD8 T cells in CVID. Here, CD1D is linked to common variable immunodeficiency.