A murine monoclonal antibody (mAb) 3C7 against integrin alpha IIb beta 3 was previously obtained as a potential antithrombotic agent in our laboratory. The epitope of 3C7 is a specific conformation of the alpha IIb beta 3 complex, but not either of the two subunits, which makes it different from abciximab, a supplementary antibody drug used in percutaneous coronary intervention which has a cross-reaction with other integrins sharing the beta 3 subunit. To reduce the human anti-mouse antibody reactions of 3C7, the variable regions of this antibody were cloned and fused with the constant counterparts of human IgG1. Two vectors of light and heavy chains were constructed and co-transfected into CHO-dhfr (-) cells. The chimeric antibody c3C7 was purified and the properties of c3C7 were compared with 3C7. Identical to its parent antibody 3C7, c3C7 binds to the alpha IIb beta 3 complex, but not to either of the subunits. The K (d) value of c3C7 was in the same order of magnitude as 3C7 (1.570 +/- 0.326 vs 0.780 +/- 0.182 nmol/L). Human platelet aggregation induced by adenosine diphosphate was effectively inhibited by c3C7 in a dose-dependent manner. In conclusion, after the modification, c3C7 retained the properties of its parent mAb with no loss of its biological activity. Therefore, c3C7 has the potential to become a novel agent for the treatment of thrombosis.