Effect of low dose methotrexate on neutrophil chemotaxis induced by leukotriene B4 and complement C5a.

When mediators of inflammation such as complement component C5a or leukotriene B4 are introduced into an air pouch created in mice, these mediators induce the migration of neutrophils into the air pouch. Pretreatment of mice with low doses of methotrexate inhibits leukotriene B4 or C5a induced neutrophil migration into the air pouch. Inhibition of neutrophil chemotaxis by methotrexate may, at least in part, account for the rapid onset of antiinflammatory activity that was observed in clinical trials with methotrexate in rheumatoid arthritis.