Objective To investigate the effect of lineal polypeptide injection on immune function of severe sepsis patients in ICU.Methods 40 severe sepsis patients in ICU were randomly divided into two groups after signed the consent form:the treatment group (20 cases)and the control group (20 cases).On the 1st day of antibiotic therapy, the patients in the treatment group were simultaneously treated with lineal polypeptide intravenous injection,while the patients in the control group received the same routine treatment,but without lineal polypeptide injection,all with a 10 days treatment course.Blood bacteria culture and drug sensitivity test were completed after entering the hospital. The scores of Sequential Organ Failure Assessment(SOFA)before treatment and at day 3,7 and 10 of therapy were evaluated.The peripheral blood of patients was taken and send to the clinical laboratory.The WBC,NEU%,PCT, hs -CRP,IL -6,total T lymphocytes (CD +3 )and T lymphocyte subgroup (CD +4 ,CD +8 ,CD +4 /CD +8 )were detected in both the treatment group and the control group.Adverse drug events were also detected in the process of therapy. Results Compared with before treatment[(5.56 ±2.03)points],after 7 days of lineal polypeptide therapy,the SOFA score of the treatment group[(3.48 ±1.83)points]decreased significantly(t =2.793,P <0.05),and after 10 days therapy,the descending degree in the treatment group was more significantly and declined earlier than the control group (t =4.401,P <0.01 ).In the aspect of improving the inflammatory markers,two groups were all improved after therapy,but the degree of improvement in the treatment group was better than the control group.After 7 days therapy,IL -6 level was (37.61 ±7.51)mg/L in the treatment group,while (50.49 ±7.68)mg/L in the control group (t =1.969,P <0.01),and the improvement of NEU% was not found in control group.In the aspect of improving the immune function,the CD +3 ,CD +4 ,CD +4 /CD +8 ratios were increased significantly [before therapy:(41.27 ±6.91)%,(19.65 ±5.29)% and (0.96 ±0.42);after 3 days therapy:(46.57 ±7.11 )%,(24.99 ± 7.70)%,(1.27 ±0.39)],and CD +8 [before therapy:(25.62 ±5.18)%,after 3 days therapy:(23.51 ±3.19)%] was decreased dramatically after 3 days of lineal polypeptide injection treatment,there was significant improvement in time and degree in the treatment group compared with the control group (t =1.390,t =1.407,t =3.974,t =2.081, all P <0.05).No severe adverse drug events were found.Conclusion As an immune modulator,lineal polypeptide injection could effectively improve the immune function of severe sepsis patients in ICU.