ABSTRACT
The immune system is intended to be injurious to invading organisms. Any response to an immunological challenge places host tissue at risk. This chapter describes evidence that there is a prominent immune response in Alzheimer’s disease (AD). It focuses on the autodestructive forces that are inherent to such a response and the potential harm they can cause. The pivotal cell in local immune reactions is the tissue macrophage which, in the case of brain, is the microglial cell. Microglial cells can be easily detected immunohistochemically by staining for leukocyte common antigen or for the FcyRI receptor. Immunohistochemical staining for the MHC glycoprotein, HLA-DR, is a particularly sensitive method of detecting reactive microglia. The accumulating evidence of a chronic endogenous inflammatory reaction in the AD brain, and particularly the abundance of the membrane attack complex, has led to the hypothesis that immune system attack is responsible for much of the neuronal destruction in AD.
