Fig. 4

Systemic administration of PD-1-Fc to type II collagen (CII)-immunized mice accelerates arthritis onset and joint damage. a Mean clinical scores of arthritis for all four limbs in collagen-induced arthritis (CIA) mice that received 50 μg (n = 7) or 150 μg (n = 7) of PD-1-Fc in phosphate-buffered saline (PBS) intravenously for 5 consecutive days beginning on day 1 after the second immunization with CII. Adjuvant-immunized controls were treated with immunoglobulin G (IgG) (n = 7). b Mean clinical scores of arthritis for all four limbs in CIA mice that received 50 μg (n = 5) or 150 μg (n = 5) of PD-1-Fc in PBS intravenously for 5 consecutive days beginning on day 1 after the first treatment. Controls were treated with IgG (n = 5). c Mean clinical scores of arthritis for all four limbs in CIA mice that received 25 μg of PD-1-Fc in PBS locally injected into the limbs (n = 3) for 3 consecutive days beginning on day 1 after the first treatment. Controls were treated with IgG (n = 3). d Photographs of CIA mice on day 39 after the second CII immunization. These animals were treated with PD-1-Fc (lower and middle photographs) or IgG (top photograph). e and f Representative computed tomographic scans of hind paws from the experiment shown in (a) at day 39 after the second immunization. g Representative hematoxylin and eosin–stained joint sections from the experiment shown in (a) on day 50 after the second immunization. PD-1 programmed cell death 1 protein