More severity, higher serology index and increased histopathological scores of PIA caused by polyI:C treatment. The arthritis clinical indexes (a) including clinical score, max clinical score, onset day, mid-paw perimeter, ankle perimeter; and serum NO and TNF-α concentration at d26 (b) were compared among the polyI:C, LPS and saline groups. (c), In representative histological images of ankle joints, the ankle joints in the control group and PIA groups treated with saline or ligands were stained by H&E. (d), For the histological analysis of synovitis, joint destruction, new bone and cartilage formation and the total histological index, the various scores were quantified among PIA groups treated with saline and ligands. Data are presented as means ± SEM. * represents the comparison between ligands treated groups and saline group in A and D, or between ligands treated groups and control group in B. But # between ligands treated groups as marked. Levels of significance were calculated using Mann-Whitney U test (n = 9 for each group, */# P < 0.05, **/## P < 0.01, ***/### P < 0.001).