In rats models of AD induced by injecting Aβ1-42 into the ventricle, Th17 cells were able to infiltrate into brain parenchyma through disrupted BBB and release the cytokines such as IL-17A, IL-22 and IL-23 in the blood and brain, the expression of brain RORγt was also upregulated, while the Treg-related cytokines such as IL-10 and TGF-β were decreased [14,50]. Here, IL17A is linked to Alzheimer disease.