Between the three groups, no significant differences were detected, although the control group showed a slightly reduced level of IgG (CTRs: 6.24 ± 2.79 mg/mL; PD patients: 7.27 ± 2.86 mg/mL; and LRRK2 carriers: 7.11 ± 3.06 mg/mL) (Figure 1A, Table 2). Here, LRRK2 is linked to Parkinson disease.