Introduction to special issue on neuroimmunology in brain development and disease

Although neural-immune cross-talk during disease and/or trauma has been studied for many years, the dogma has been that there is little interaction between the immune and nervous systems in healthy individuals. This belief was historically based on indications that the blood-brain barrier (BBB) blocks immune cell infiltration into the central nervous system (CNS), leading to limited immune responses in the CNS, and by a lack of classical immune proteins in the brain (Murphy and Sturm, 1923; Joly et al., 1991). However, recent observations from both clinical and basic science research have caused a paradigm shift in our understanding of neural-immune interactions, indicating clearly that there is extensive communication between these systems (McAllister and van de Water, 2009). There is now clear evidence that environmental insults that alter the immune response can affect brain development as well as behavior (Patterson, 2009; Meyer et al., 2011). Moreover, mouse models of neurodevelopmental disorders have provided strong support for immune involvement in CNS development and disease (Patterson, 2009; Patterson, 2011). Finally, several different kinds of immune molecules, including cytokines, major histocompatibility complex (MHC) proteins, and complement, are expressed in the developing and adult brain and have critical functions in brain development and plasticity (Garay and McAllister, 2009; Shatz, 2009; Elmer and McAllister, 2012; Stephan et al., 2012). In this Special Issue, we include reviews covering a range of topics from epidemiology indicating a role for immune dysregulation in neurodevelopmental disorders to basic mechanisms underlying the effects of immune molecules in brain development and disease