Alzheimer's disease (AD) is the most common neurodegenerative disorder. 
Currently available therapies are symptomatic but do not alter underlying 
disease progression. Immunotherapeutic approaches such as anti Aβ peptide active 
vaccination trials have had limited success to date. Intravenous immunoblobulin 
(IVIg) is widely used in immune-mediated neurological disorders such myasthenia 
gravis and Guillain-Barre syndrome. These preparations have been obtained from 
the pooled plasma of healthy human donors and contain natural anti-amyloid 
antibodies and are well tolerated. A small pilot study of passive immunotherapy 
using IVIg has suggested cognitive improvement. A multicenter phase III trial is 
ongoing and will determine whether or not this treatment can ameliorate 
cognitive deficits in mild-to-moderate AD. Here, we briefly review the 
pathogenic role of amyloid and tau in AD, as well as immunotherapeutic efforts 
to date. We also summarize what is known about naturally occurring anti-Aβ and 
tau antibodies in IVIg with a view toward explaining potential mechanisms 
underlying their therapeutic effects.