In addition, IgG1 and IgG3 levels were significantly increased in IHD patients (IgG1 = 1.1 × 107 vs 4.5 × 106 ng/mL, P < .0001, IgG3 = 1.3 × 106 vs 6.0 × 105 ng/mL, P = .002; Figure 5D‐E). Here, IGHG3 is linked to myocardial ischemia.