Microglial Activation Resulting from CD40-CD40L Interaction After β-Amyloid Stimulation

Alzheimer's disease (AD) has a substantial inflammatory component, and activated microglia may play a central role in neuronal degeneration. CD40 expression was increased on cultured microglia treated with freshly solublized amyloid-beta (Abeta, 500 nanomolar) and on microglia from a transgenic murine model of AD (Tg APPsw). Increased tumor necrosis factor alpha production and induction of neuronal injury occurred when Abeta-stimulated microglia were treated with CD40 ligand (CD40L). Microglia from Tg APPsw mice deficient for CD40L demonstrated reduction in activation, suggesting that the CD40-CD40L interaction is necessary for Abeta-induced microglial activation. Finally, abnormal tau phosphorylation was reduced in Tg APPsw animals deficient for CD40L, suggesting that the CD40-CD40L interaction is an early event in AD pathogenesis.