Increased lymphangiogenesis in joints of mice with serum-induced arthritis. Wild-type mice received serum from K/B × N mice to induce arthritis and were sacrificed at 0, 14, and 35 days after serum injection (n = 3 or 4 mice at each time point). Ankle joint sections were immunostained with anti-LYVE-1 antibody. (a) Representative pictures show inflamed pannus and large numbers of LYVE-1+ lymphatic vessels in an adjacent section (pink arrows) at day 35. (b) The area and number of lymphatic vessels within the pannus were determined by histomorphometric analysis. Values are the means plus standard deviation of 3 or 4 mice at each time point. H&E, hematoxylin and eosin; LYVE-1, lymphatic endothelial hyaluronan receptor 1.