IFNG and Bruton-type agammaglobulinemia: This was confirmed here: serum IFN-γ levels were significantly elevated in these individuals with CVID when compared with other patients with CVID, patients with XLA, and healthy controls (mean 228.6 pg/mL, 118.6 pg/mL, 182.8 pg/mL, and 109.5 pg/mL, respectively, P < 0.0001, Figure 5A).