Fig. 3
From: Immunosenescence: signaling pathways, diseases and therapeutic targets
Immunosenescence in neurodegenerative diseases. In AD, immunosenescence and inflammaging drive chronic neuroinflammation, fostering neuronal damage and impairing Aβ clearance via dysfunctional microglia. Aβ deposition triggers the uncontrolled activation of microglia and astrocytes. Increased BBB permeability allows Th1/Th17 infiltration and the secretion of proinflammatory cytokines, exacerbating neurodegeneration, whereas Tregs help suppress inflammation and clear Aβ. In PD, misfolded α-synuclein aggregates into Lewy bodies, causing dopaminergic neuron loss in the substantia nigra. Peripheral CD4⁺ T cell infiltration and IL-17 signaling drive neuroinflammation and neuronal apoptosis. Activated microglia amplify this process by fostering a proinflammatory environment, whereas reduced Tregs fail to suppress excessive immune activation
