Finally, as to the origin of these brain-reactive autoantibodies, since microbial transglutaminase (mTG) and tissue transglutaminases (tTG) have been shown by earlier studies to be involved with celiac and other autoimmune disorders [22–24], we theorized that perhaps some of these autoantibodies may arise from reactivity with mTG or cross-reactivity between enteric neuronal antigens and those that are expressed in the brain [46]. The gene discussed is TGM2; the disease is autoimmune disease.