Increasing evidence indicates that the central nervous system (CNS) can operate certain immune functions. There is a bidirectional regulation system between the brain and peripheral immune system during infection and inflammation. Furthermore, autopsy brain preparations in Alzheimer's disease patients show the up-regulated expression of proinflammatory cytokines, suggesting an important role of cytokines in disease progression. Recently, acetylcholine has been suggested to inhibit lipopolysaccharide (LPS)- induced inflammation in macrophages. In this paper, we review the important aspects of several cytokines under the pathologic conditions of CNS. Furthermore, we discuss recent views on the nonneuronal action of acetylcholine in the cross talk between acetylcholine and the immune system.