Objective The present study investigates the impact of fibronectin(Fn) on the inflammatory factor release of human peripheral blood mononuclear cells(PBMCs) and TLR4 expression.Methods Gradient centrifugation was used to separate normal PBMCs from concentrated human PBMCs.The blank control,Fn stimulus,LPS stimulus,and Fn plus LPS complex stimulus groups were established to stimulate the PBMCs for 0.5,2,4,8,and 12 h,respectively.Subsequently,cell culture supernatant samples were collected to test the inflammatory factors IL-6,IL-10,and TNF-α using ELISAs,and Western blot was used to detect the effect of every stimulus on Toll-like receptor 4(TLR4) expression.Results At the 4 and 8 h time points,the IL-6 production in the Fn plus LPS group reached 727±37.73 and 918.25±26.78 pg/ml,respectively,which were much higher than those in the other groups(P < 0.05).Moreover,the TNF-α production in the Fn plus LPS group increased 2 h after stimulation and was significantly higher than those in the other three groups(P < 0.05).The IL-10 productions in the Fn plus LPS group showed a slowly increasing trend at the 0.5,2,and 4 h time points and reached 784.74±91.96 and 1081.74±57.98 pg/ml at the 8 and 12 h time points,respectively.Again,these results were significantly higher than those in the other groups(P < 0.05).The Western blot analysis showed that the expression level of TLR4 in the complex stimulus group was evidently higher than those in the other three groups at each time point(P < 0.05).Conclusion Fn or LPS stimulation can therefore promote the expression of TLR4 in PBMCs.However,their combination can remarkably increase the expression of TLR4 and the production of IL-6 and TNF-α.These results imply that Fn can enhance the sensitivity of PBMCs to LPS.