Objective       To investigate the effect of anticoagulant and anti-inflammatory fusion protein TAP-SSL5 (tick anticoagulant peptide and staphylococcal superantigen like protein-5) on the binding of platelet microparticles (PMPs) to human acute monocytic leukemia cell line THP-1 and the activation of Mac-1.        Methods        PMPs

were generated by adenosine diphosphate (ADP) activating human platelets. Flow cytometry (FCM) was used to identify PMPs by PE labeled mouse anti-human CD62P monoclonal antibody and FITC-Annexin V

and to check the activation and phosphatidylserine (PS) by FITC labeled mouse anti-human CD41 monoclonal antibody and PE labeled mouse anti-human CD151 monoclonal antibody (CD40L). The mitochondrial membrane potential in human platelets was checked with JC-1 kit. The binding rates of PMPs to THP-1 cells and the conformation change of Mac-1 (CD11b/CD18

αMβ

2

) after co-incubation with PMPs were assayed by FCM.       Results       Both CD62P and PS were positive on PMPs. The positive rates of CD41 and CD40L on the ADP-induced PMPs were 50.8% and 44.0% respectively. While there was no significant change on the mitochondrial membrane potential in ADP activated platelets (

P

0.05). The binding rates of PMPs to THP-1 cells and the activation rates of Mac-1 on THP-1 cells were (24.80±5.16)% and (21.17±5.92)% respectively

which decreased to (13.67±2.15)% and (0.99±0.62)% after the THP-1 cells were pre-incubated with 10 mg/L TAP-SSL5 (

P

0.05 and

P

0.01).       Conclusion       TAP-SSL5 directly inhibits the binding of PMPs to THP-1 cells

and subsequently inhibits the activation of Mac-1 on THP-1 cells.