Objective : To observe the immune protection of matrine (Mat) on a rat model of chronic Pseudomonas aeruginosa (PA) biofilm pneumonia. Method : Rats were challenged intratracheally with alginate embedded PA strain PAO579 in the concentration of 1×109 colony-forming units per milliliter(CFU ·mL-1). Mat or sterile normal saline (NS) was injected intraperitoneally once a day for two weeks starting on the second day after challenge. Two weeks post intratracheal challenge with PA

parameters were evaluated. Result : Two weeks after challenge

the Mat-treated group showed a significantly milder pathological changes in lung(P<0.001)

and lower lung abscess incidence compared to the model group(P<0.001). Furthermore

a remarkable improved bacterial clearance(P<0.001) and a shift from an acute type to a chronic type of lung inflammation were found in the Mat-treated group compared to the model group. 80% animals have returned to a chronic type of lung inflammation after Mat treatment which were much higher than that in the model group(P<0.05).The lung cells from the Mat-treated group produced more interferon-gamma(IFN-γ)(P<0.001)

but less interlerkin-4(IL-4)(P<0.001)as compared to the model group. These results indicate that Mat has an effect of inducing Th1 type of immune response. Conclusion : Mat treatment significantly reduced pathological changes in lung and enhanced lung bacterial clearance

which might be associated with a shift of local immune responding type from a Th2 like to Th1 like. This might provide a better immune protection to the rats with chronic P. aeruginosa bilfilm lung infection.