Peripheral Humoral Immune Response Is Associated With the Non-motor Symptoms of Parkinson’s Disease

BACKGROUND: Non-motor symptoms are common in Parkinson’s disease (PD) and can even be used as part of the supportive criteria for diagnosis. Chronic inflammation is involved in every stage of PD. Disorders of the immune system affect the peripheral blood. Whether the humoral immune response is associated with the non-motor symptoms of PD remains unknown. METHODS: Mann–Whitney tests and Bonferroni correction were used to compare the serum levels of IgG, IgA, IgM, C3, and C4 between 180 sporadic PD patients and 187 healthy controls. Multiple regression models were conducted to assess the associations among these indicators of humoral immunity and the clinical features of PD patients. RESULTS: Male PD patients had lower levels of C3 and C4 than healthy controls [0.87 (0.22) vs. 0.96 (0.19); 0.19 (0.06) vs. 0.22 (0.07), respectively, Pc < 0.01] and lower levels of C3 than female PD patients [0.87 (0.22) vs. 1.02 (0.23), Pc < 0.01]. Patients suffering from attention/memory problems had significantly lower levels of IgA and C3 than those without these problems [1.92 (1.21) vs. 2.57 (0.76); 0.89 (0.24) vs. 0.97 (0.24), respectively, Pc < 0.04]. In addition, serum IgG levels were negatively associated with mood/cognition problem scores and were positively associated with gastrointestinal tract problem scores (adjusted R(2) = 0.063, F = 1.805, p = 0.038). Serum C3 levels were negatively associated with being male, age, and sleep/fatigue problem scores (adjusted R(2) = 0.123, F = 2.678, p = 0.001). CONCLUSION: The peripheral humoral immune response might be correlated with the non-motor symptoms of PD.