Abstract： Objective To investigate the biological effect of GM-CSF on splenic dentritic cells (DCs)when used to treat severe sepsis and the influence on the prognosis.Methods All 160 male Kunming mice were randomly(random number)divided into four groups:control group(n =50),the mice didnt receive special treatment; CLP group(n =42),the mice underwent cecal ligation and puncture;conventional treatment group(n =34),the mice received intraperitoneal injection of 5 mg/kg ceftriaxone at 12,24,36,48,60,72 and 84 h after surgery; GM-CSF treatment group(n =34),the mice received hypodermic injection of 20 μg/kg GM-CSF besides ceftriaxone at 12,36,60,and 84 h after surgery.The mice were sacrificed at 0,12,24,48 and 72 h after CLP by cervical dislocation.The amount of splenic DCs and apoptosis rate were measured by flow cytometry,and the serum concentrations of IL-12 were detected by ELISA in each group.Meanwhile the survival prognosis was observed at 96 h.Results At every time point,the apoptosis of splenic DCs increased and the amount markedly reduced in severe sepsis(P ＜0.05),the serum concentration of IL-12 increased on an one-way curve type(P ＜0.05).The treatment of cephalosporin exacerbated the loss of DCs(P ＜ 0.05),while hadnt any effect on IL-12(P ＞ 0.05).GMCSF treatment increased the amount of DCs(P ＜ 0.05),and decreased IL-12 concentrations(P ＜ 0.05).The OR of GM-CSF was 0.079 computed by Logist regression analysis.Conclusions GM-CSF treatment severe sepsis can increase the amount of splenic DCs,decrease serum levels of IL-12,and improve prognosis.