Wild-type mice, A2A receptor knockout mice or A3 receptor knockout mice were treated with either weekly injections of methotrexate (0.75 mg/kg) or saline control for 4 weeks prior to induction of inflammation. Inflammatory exudates were induced in the peritoneum of mice, as described. After 4 hours the exudates were collected and the adenosine levels quantitated. Wild-type data are a combination from both mouse strains. *P < 0.0001 vs wild-type control mice, Student's t test; **P < 0.0001 vs A2A knockout control mice, Student's t test; †P < 0.0001 vs A3 knockout control mice, Student's t test.