Objective To investigate the effects of adiponectin (APN) pretreatment on the peripheral blood polymorphonuclear leucocyte (PMN) CD1 1b expression and respiratory burst activity in septic rats.Methods Seventy-two male Sprague-Dawley rats,weighing 250-300 g,were randomly allocated into 3 groups (n =24 each) using a random number table:control group (C group),cecal ligation and puncture (CLP) group and APN pretreatment group (APN group).Sepsis was induced by CLP in CLP and APN groups.In APN group,recombinant adiponectin 6 mg/kg was injected intraperitoneally at 12 h before CLP.Eight rats in each group were randomly chosen at 6,12 and 24 h after operation to collect venous blood samples for measurement of the peripheral blood PMN CD11 b expression and respiratory burst activity with flow cytometry.The apoptosis rate was detected with Annexin-V/PI double staining.The animals were sacrificed at 24 h after operation and pulmonary specimens were obtained to detect myeloperoxidase (MPO) activity in lung tissues.Another 10 rats in each group were chosen and treated according to the method mentioned above,and the survival rates within 7 days after operation were observed in the three groups.Results Compared with C group,the expression of CD11b on PMNs was significantly up-regulated,the PMN respiratory burst activity and MPO activity were increased,and the apoptosis rate and survival rate within 7 days after operation were decreased in CLP group (P ＜ 0.05).Compared with CLP group,the expression of CD11b on PMNs,PMN respiratory burst activity and MPO activity were significantly decreased,and the apoptosis rate of PMNs at 6 h after the operation and survival rate within 7 days after operation were increased in APN group (P ＜ 0.05).Conclusion Adiponectin pretreatment can attenuate sepsis-induced inflammatory responses and the mechanism may be related to inhibition of excessively activated PMN adhesion CD11b expression during sepsis and respiratory burst activity and promotion of apoptosis in rat PMNs.