Single nucleotide polymorphisms have been analysed in many cytokines, in particular, those that are associated with altered levels in schizophrenia such as TNF-α, IL1-β, IL-6, IL-10, INF-γ, and in the genes encoding the immune system regulatory proteins CTLA-4 and CD28 [33–37]. This evidence concerns the gene CTLA4 and schizophrenia.