C4A and bipolar disorder: In addition to CRP variants, other recent studies have identified several inflammatory genetic variants associated with schizophrenia and bipolar disorder, which include variants in the major histocompatibility complex (MHC) region on Chromosome 6p21 [72]—harboring many cytokine genes [54,73–76]—and in the IL10 promoter [77], TNF promoter [78], IL1B [79], and C4 [80].