Histologic findings in the ankle joints of Tg197 mice. (a,b) Untreated mice: (a) partially altered articular cartilage (crt) with bone erosion (arrowhead), and presence of inflammatory infiltrates (arrow) in the synovial (syn) tissue; (b) extensive articular cartilage destruction and bone erosion (arrowhead). (c,d) P-NT.II-treated mice: (c) minor cartilage changes (crt) with absence of bone erosion; (d) focal articular cartilage destruction (crt) and minor bone erosion (arrowhead). (e,f) Mice treated with scrambled P-NT.II: (e) the joint cavity (jc) is lined with synovitis (*); (f) cartilage destruction and bone erosion (arrowhead) are present, along with inflammatory infiltrates (arrow). Nontransgenic controls showed normal joint structures throughout the study (data not shown). (Hematoxylin & eosin staining; original magnification ×25 in a, e, f; ×10 in b, c, d. Bars = 500 μm).