Abstract: Objective To observe and search whether the patients fall into SAP with PICS will suffer more serious immunosuppression or not compared with those without PICS through clinical and laboratorial evidence and offer the reference to clinical diagnosis. Methods This study was about 63 SAP patients.According to academic reports，SAP patients were divided into PICS group with 23 patients and non-PICS group with 40 cases.We considered patients occur immunosuppression if they suffered secondary infections.Blood samples were collected to examined concentrations of ALCs and spd-l1. Results Compared with the control group，the ALCS count of SAP patients decreased significantly within 3 weeks after admission（P < 0.05），and the level of SPD L1 increased significantly within 1 month.Secondary infections occurred overall in the PICS group，compared with only 27.5% in the non-PICS group（P<0.05）.There was no statistical difference in ALCs and sPD-L1 between two groups in the early stage of onset of SAP.However，after 2 weeks there is significant difference in ALCs and sPD-L1 in SAP patients with PICS and without PICS. Conclusion SAP patients with PICS suffer from more severe immunosuppression with higher incidence of secondary infections.

Key words: severe acute pancreatitis, persistent inflammation immunosuppression catabolism, absolute lymphocyte counts, sPD-L1, immunosuppression