Abstract 2601: Increased TLR-4+ Monocytes in Thrombi from the Site of Coronary Occlusion in Acute Coronary Syndromes - a Role for Innate Immunity in Acute Coronary Syndrome

Objective: To evaluate and compare the expression of Toll-like receptors 2 and 4 (TLR-2 and -4) in thrombi obtained at the site of coronary occlusion of patients with acute coronary syndrome (ACS) with their expression in peripheral blood (PBL) of the same patients and healthy controls. Methods: Thrombi were mechanically disrupted, treated with actilyse for 12 hours in RPMI + 10% FCS. The amount of erythrocytes was reduced by isotonic lysis. Peripheral blood from the same patients (n = 14) and from age- and sex-matched healthy controls (n = 10) were treated in the same manner. Adherent cells were detached by Accutase and mixed with the non-adhering cells. CD14+ and CD66b+ (FITC) cells were stained for TLR-2 and TLR-4 (PE) and analysed by flow cytometry. Results: TLR-4 was detected in the thrombi by immunohistochemistry. The proportion of TLR-4+ cells was markedly increased in the monocyte gate of cells isolated from the thrombus, in comparison to peripheral blood cells from the same patient or healthy controls. Most importantly, the expression of TLR-4, measured as the mean fluorescence intensity, was significantly elevated on CD14+ monocytes of the thrombus, compared to peripheral blood CD14+ cells from the same patient or healthy controls (Figure 1 ). No such differences could be found for expression of TLR 2, TLR 3 or TLR 9. Conclusion: Thrombi of patients with ACS contain an increased proportion of TLR-4+ monocytes. Thus, our results suggest that activation of innate immunity through TLR-4 is involved in ACS. This may be a part of a link between induction of heat shock proteins and thrombosis.