Our data provide a mechanistic explanation for the previously described therapeutic efficacy of systemic IFN-γ administration in inflammatory diseases including psoriasis (Cannon et al., 1989, Fierlbeck and Rassner, 1990, Fierlbeck et al., 1990, Morhenn et al., 1987, Stevens et al., 1998, Veys et al., 1997). The gene discussed is IFNG; the disease is psoriasis.