Blocking TNF-α prevents the development of inflammatory arthritis in DNase II^−/−STING^S365A/S365A mice. (A–C) 6-wk-old DNase II^−/−STING^S365A/S365A female mice received rat IgG or anti–TNF-α (40 µg/g body weight) i.p. once a week (n = 5 in each treatment group). (A) Arthritis scores were assessed every week (mean ± SD, n = 5 per group). Statistical analysis was done using a two-tailed, unpaired Student’s test. *, P < 0.05 between anti–TNF-α– and rat IgG–treated mice. (B) Incidence rates of arthritis (mean ± SD, n = 5 in each group). (C) qRT-PCR analysis of inflammatory cytokines in mouse paws (mean ± SD, n = 5 in each group). Each dot represents a mouse. (D and E) 5-mo-old male DNase II^−/−STING^S365A/S365A mice displaying polyarthritis received rat IgG or anti–TNF-α (20 µg/g body weight) twice a week (n = 4 in each group). (D) Arthritis scores were assessed weekly (mean ± SD, n = 4 per group). *, P < 0.05 between rat IgG– and anti–TNF-α–treated mice. (E) qRT-PCR analysis of inflammatory cytokines in mouse paws (mean ± SD, n = 4 per group). Statistical analysis was done using a two-tailed, unpaired Student’s test. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001. Results are representative of two independent experiments. Ct, cycle threshold.