Objective To investigate the effect of lipopolysaccharide (LPS) on inflammatory cytockine interleukine-6 (IL-6) expression in peritoneal macrohages from young and aged mice both in vitro and in vivo.Methods Two age groups (young group:2-month-old,old group:18-month-old) were divided into two groups,respectively:LPS treated groups were peritoneally injected with LPS and control groups was treated with PBS.Twenty-four hours later,mice were killed and then the peritoneal cavity was flushed for peritoneal macrophages to investigate the expression level of IL-6 by real-time PCR.Macrophages from control groups were cultured and treated with PBS (control) or LPS in vitro for another 24 hours,and then cell culture supematant was collected to analyze IL-6 concentration by ELISA.Results IL-6 expression in macrophages from natural aged mice (control) were significantly higher than young mice ( t =-18.538,P ＜0.01 ).After LPS treatment in vivo,the expression of IL-6 increased much in both of the two age groups,but it was much lower in aged group compared to young group (t =6.124,P ＜00.01 ).When cultured in vitro,the function of IL-6 secretion in macrophage from aged group decrease significantly compared to young group,no matter in control or LPS-treated status (t =12.329 and t =5.876,P ＜ 0.05 ).Conclusion Sustained and high level of IL-6 in macrophage was expressed in aged group.While after LPS stimulation,the ability of IL-6 production declined significantly.Once out of the intemal environment,macrophages of aged mice appeared lower ability of IL-6 secretion and immunity function disorder.