There is increasing evidence for the involvement of herpes simplex virus type 1 and human cytomegalovirus in the cognitive impairment of patients with schizophrenia (SCZ). Both herpes simplex virus type 1 and human cytomegalovirus have evolved strategies for decreasing the efficacy of the host immune response and interfering with viral clearance. Immunoglobulin GM genes, genetic markers of IgG heavy chains located on chromosome 14, modify certain immunoevasion strategies of these viruses. Particular GM alleles are also associated with antibody responsiveness to gliadin or gluten sensitivity, an attribute reported to be prevalent in a significant proportion of SCZ patients. On the basis of these properties, I hypothesize that GM alleles are risk factors for SCZ and their evaluation could help genetically dissect the disease in different subsets and/or help unify some disparate areas of pathobiology (e.g. cognitive dysfunction and gluten sensitivity) affected in this disorder.