BWF1 mice at age 22 weeks (defined as “late” treatment in the legend) that had anti-dsDNA Ab, but proteinuria <2+ on urinary dipstick, were treated with 3 intraperitoneal injections of anti-PD-1 Ab at 100 μg per injection every other day. (A) Proteinuria over time in all treatment groups (“early” group was treated with anti-PD1 at 10 weeks of age). Onset of proteinuria was delayed in mice treated either early or late, although early treatment had a better effect. Controls were mice with late treatment with IgG matched to anti-PD1. (p < 0.0001, logrank test; anti-PD-1 (late) vs IgG isotype, anti-PD-1 (early) vs IgG isotype, anti-PD-1 (late) vs, anti-PD-1 (early), p < 0.01, Bonferroni method). (B) Mice with early and late treatment had prolonged survival when compared with the IgG isotype controls, (p < 0.0001, logrank test; anti-PD-1 (late) vs IgG isotype, anti-PD-1 (early) vs IgG isotype, p < 0.001, anti-PD-1 (late) vs anti-PD-1 (early), n.s., Bonferroni method). n = 20 mice per group in each experiment.