Immunopathogenesis of NMDA receptor encephalitis.

N-methyl-d-aspartate receptor encephalitis is a prototypic, primarily monophasic autoimmune disorder mediated by autoantibodies. Here, we review the basic immunological characteristics of the disease and discuss current and future means of targeted immunotherapy. Two important initiating factors have been recognized, ovarian teratomas (present in around 20%) and herpes simplex virus encephalitis (followed by autoimmune N-methyl-d-aspartate receptor encephalitis in around 23-33%). Experiments of passive monoclonal / polyclonal human antibody transfer as well as active immunization have undisputedly demonstrated pathogenicity of antibodies mainly targeting the NR1 subunit. Autoreactive B cells can be found in the periphery, the cerebrospinal fluid, teratomas, as well as cervical lymphnodes. Their phenotype includes memory B cells and autoantibody-secreting cells; they are often clonally expanded and antigen-experienced, however somatic mutation is not a prerequisite for antigen binding. These findings underscore the importance of early immunotherapy in order to interrupt the immune response generating pathogenic antibodies.