Inflamed knee joints, various days after IFN-γ-stimulated ICA in p47phox-/- mice and controls. The numbers of cells present in the synovium (infiltrate) and in the joint cavity (exudate) were determined on an arbitrary scale from 0 to 3: 0, no cells; 1, few; 2, moderate; 3, maximal. (a) Numbers of cells; (b) wild-type controls; (c) p47phox-/- mice. The number of cells was determined by two blinded observers. Data are means ± SD for eight animals. Significance was tested with the Wilcoxon rank test (*P < 0.05). Original magnifications × 100. F, femur; P, patella. Note that there is a comparable cell mass in arthritic knee joints of p47phox-/- mice and wild-type controls.