In our model of arthritis, results from immunofluorescence assay showed an increase of cFos expression in the dorsal spinal cord at days 28 (PID 21) and 42 (PID 35) after the initial immunization (PID 21: 34.97 ± 1.13 vs.26.67 ± 1.17; CIA+Vehicle group vs. Naive group; P < 0.01) (Fig. 2A, B) (PID 35: 31.84 ± 1.08 vs.27.21 ± 1.31; CIA+Vehicle group vs. Naive group; P = 0.021) (Fig. 2A, C). Here, FOS is linked to arthritic joint disease.