Objective To explore the immune mechanism of Tibetan medicine Twelve Flavors Yishou San in intervening with acute lung injury.Methods Construct a lipopolysaccharide(LPS)-induced acute lung injury rat model and treated it with Twelve Flavors Yishou San.The intervention effect of Twelve Flavors Yishou San on LPS induced acute lung injury was determined through lung pathological sections and blood gas analysis.Enzyme linked immunosorbent assay(ELISA)was used to detect the expression of pro-inflammatory cytokine tumor necrosis factor-α(TNF-α)and anti-inflammatory cytokine interleukin(IL)-10 in rat's bronchoalveolar lavage fluid.Flow cytometry was used to detect changes in immune cells in rat's bronchoalveolar lavage fluid,lungs,spleen and peripheral blood.Results LPS successfully induced an acute lung injury model in rats,and Twelve Flavors Yishou San could alleviate the exudation of inflammatory cells,elevated oxygen partial pressure in LPS induced acute lung injury to varying degrees.The ELISA results of rat bronchoalveolar lavage fluid showed that compared with normal control group,the TNF-α level in the bronchoalveolar lavage fluid of rats with acute lung injury was increased and the IL-10 level was decreased,while the Twelve Flavors Yishou San could alleviate this effect.The results of flow cytometry showed that Twelve Flavors Yishou San could significantly reduce neutrophil infiltration in rat bronchoalveolar lavage fluid,but had no significant effect on macrophages and adaptive immune response.Conclusion Twelve Flavors Yishou San can alleviate LPS induced acute lung injury by inhibiting neutrophil infiltration,providing an important experimental basis for fully understanding the therapeutic mechanism of Twelve Flavors Yishou San.