CD19 and schizophrenia: The largest GWAS of schizophrenia to date has shown that in addition to genes expressed in the brain, schizophrenia is associated with genes involved in adaptive immunity (CD19 and CD 20 B-lymphocytes) and the major histocompatibility complex (MHC) region on chromosome six (Schizophrenia Working Group of the Psychiatric Genomics, 2014).