CCL22 and Parkinson disease: Linear regressions assessing a relationship between CCL22 content and ferritin abundance parsed apart by disease group revealed a significant relationship in IBD (R2 = 0.56, p= 0.0020) and PD (R2 = 0.38, p= 0.014) and NHC (R2 = 0.42, p= 0.042) where individuals with low CCL22 also had low ferritin across all participant groups (Fig. 5Bii).