Figure 3. IL-1β-deficient mice had decreased neutrophil recruitment to the infected knee joints compared with wt mice.

The right knee joints of IL-1β^−/− and wt mice were inoculated with 1×10³ CFUs of S. aureus in the presence of an orthopaedic-grade K-wire implant. The infected joint tissue was harvested on postoperative day 1. (A) Representative photomicrographs of histologic sagittal sections of wt mice (top panels) and IL-1β^−/− mice (bottom panels) are shown (1 of 3 mice per group, with similar results). Left large panels: low magnification (12.5x) of H&E-stained joint specimens with a line drawing of the location of the implant extending into the joint from the femoral canal. Upper right small panels: higher magnification (100x) of H&E-stained joint specimens of the boxed area in the left panel at the location of the intra-articular end of the implant. Lower right small panels: higher magnification (400x) of H&E-stained sections in the boxed areas in the upper right panels. (B) Mean myeloperoxidase activity of the infected joint tissue specimens (ng/mg of tissue) ± sem (n=5 per group). ‡p<0.001 IL-1β^−/− versus wt mice.