C4A and schizophrenia: In fact, these data have led to the development of a cytokine-based model of schizophrenia [41], which gains additional support from the characterization of the common genetic liability for schizophrenia associated with the major histocompatibility complex (MHC) and complement Component 4 (C4) genes according to large-scale genome-wide association studies (GWAS) [42].