Aim To investigate a potential role of Toll-like receptor 2(TLR2) and platelet factor 4(PF4) in atherosclerosis,We assessed their expression in murine atherosclerotic plaques.Methods Twenty apolipoprotein E-/-mice at the age of 12 weeks were fed by high-fat diet,ten C57BL/6 mice at the age of 8 weeks were fed by standard laboratory chow for 12 weeks,then all of the animal were euthanized.Blood was sampled from the eye,the serum lipids was enzymatically detected.The thoracic and abdominalis aorta was fixed by in situ liquid flow.Thoracic aorta was fix in 10% formalin,paraffin imbedding,serial sections,and HE staining.Aortic lesions of high-fat diet-fed apolipoprotein E-/-mice were examined for TLR2 and PF4 expression by immunohistochemistry.Results Aortic atherosclerotic lesions in all apolipoprotein E-/-mice expressed TLR2,whereas aortic tissue obtained from control C57BL/6J mice showed no TLR2 expression.Serial sections immunostaining showed TLR2 localizing with macrophages and endothelial cells in murine atherosclerotic lesions.Furthermore,PF4 expression in murine atherosclerotic plaques were also observed.Conclusions TLR2 is expressed by macrophages and endothelial cells in murine atherosclerotic lesions,and we find that PF4 is also expressed in the plaques.They may play a role to enhance and sustain the innate immue and inflammatory responses.