Figure 1

u-PA^-/- mice are resistant to K/BxN serum transfer arthritis but display monoarticular arthritis following the addition of an intra-articular injection. C57BL/6 and u-PA^-/- mice with K/BxN serum transfer arthritis were either left untreated or given an intra-articular injection of saline. Mice were sacrificed 10 days later. (a) Macroscopic knee score. (b) Representative histological pictures (hematoxylin and eosin) of knee joints. Quantification of (c) cellular infiltration and (d) bone erosions in knee joints. Results are expressed as the mean ± standard error of the mean (five mice per group). *P = 0.002, u-PA^-/- versus C57BL/6 mice; **P = 0.002, ***P < 0.05, saline-treated versus untreated mice. u-PA^-/-, urokinase-type plasminogen activator gene-deficient.