K/BxN serum-transfer mouse model of arthritis

Serum from K/BxN mice, generated from breeding KRN TCR-transgenic mice with NOD/Lt mice, was collected and pooled. To induce arthritis, arthritogenic K/BxN serum (150 μl) was intraperitoneally injected into female C57BL/6 mice, aged 8 weeks. Simultaneously, mice started to receive tofacitinib (50 mg/kg), baricitinib (10 mg/kg), or vehicle twice daily per oral gavage for 2 weeks. A non–serum-induced healthy control group accompanied the experiment. Mice were scored for weight, grip strength, redness and swelling of hind paws (termed arthritis score) according to Chondrex, and footpad thickness and ankle thickness of hind paws monitored with dial thickness gauge (Peacock).