PDCD1 and psoriasis: MR16-1-treated PD-1−/− mice showed significantly less IMQ-induced psoriasis-like dermatitis compared to IgG Ctrl-treated PD-1−/− mice as evaluated by ear swelling (7.0 ± 0.6 μm vs. 15.7 ± 1.8 μm, P = 0.0013 by two-way ANOVA) and PASI score (4.5 ± 0.6 vs. 7.3 ± 0.8, P = 0.005 by two-way ANOVA) at day 7.