It was found that the presence of peptidoglycan (PG)-specific Th1 cells in psoriatic lesions that recognize streptococcal or staphylococcal PG in an HLA-DR-restricted manner and secrete IFN-γ, with enhanced PG recognition exacerbating streptococcus-induced psoriasis [152,153]. The gene discussed is IFNG; the disease is psoriasis.