Increasing evidence suggests that inflammatory and immune components in brain 
are important in Alzheimer's disease (AD) and anti-inflammatory and 
immunotherapeutic approaches may be amenable to AD treatment. It is known that 
complement activation occurs in the brain of patients with AD, and contributes 
to a local inflammatory state development which is correlated with cognitive 
impairment. In addition to the complement's critical role in the innate immune 
system recognizing and killing, or targeting for destruction, complement 
proteins can also interact with cell surface receptors to promote a local 
inflammatory response and contributes to the protection and healing of the host. 
On the other hand, complement activation also causes inflammation and cell 
damage as an essential immune function to eliminate cell debris and potentially 
toxic protein aggregates. It is the balance of these seemingly competing events 
that influences the ultimate state of neuronal function. Our mini review will be 
focusing on the unique molecular interactions happening in the AD development, 
the functional outcomes of those interactions, as well as the contribution of 
each element to AD.