In AD, keratinocytes have been found to release high levels of ß-defensins, Thymic stromal lymphopoietin (TSLP) and antimicrobial peptides, which in turn facilitate the release of histamine and other immunoregulatory mediators via MRGPRX2 (19, 22, 29, 30). The gene discussed is MRGPRX2; the disease is Alzheimer disease.