IL-1Ra treated mice had more histological signs of septic arthritis.

<p>NMRI mice inoculated with <i>S</i>. <i>aureus</i> Newman strain (1.1–1.7 × 10⁶ cfu/mouse) were treated with anakinra (IL-1 Ra 4mg/mouse, n = 30), or PBS (n = 25) every day starting on day 7 before inoculation with bacteria and continuing until the animals were sacrificed on day 10. (A) Histological evaluation (including the synovitis scores and bone erosion scores) of the joints from all 4 limbs on 10 days after infection. (B) Left panel: A micrograph of histologically intact midfoot joints from a NMRI mouse inoculated with <i>S</i>. <i>aureus</i> strain Newman that was treated with PBS. Right panel: A micrograph of a heavily inflamed midfoot joints with bone and cartilage destruction from a NMRI mouse with septic arthritis treated with anakinra. Hematoxylin/eosin was used for staining; * indicates heavely inflamed synovium; Arrow indicates the bone erosion; S, synovial tissue. Statistical evaluations were performed using the Mann–Whitney <i>U</i> test. Data were presented as scatter dot plot with median; ns = not significant.