Abstract 567: Reactive Immunoglobullin M At the Site Of Coronary Occlusion In Patients With St Elevation Myocardial Infarction
Objective: In-situ activation of complement in infarcted myocardium is one of the mediators of ischemia-reperfusion injury. IgM is known to fix complement avidly and activate the classical pathway. We aim to evaluate the presence of reactive IgM antibodies at the site of coronary occlusion in patients with ST elevation myocardial infarction (STEMI).
Method: Paired sera (n=26), obtained by aspiration and filtration from the occluded infract related coronary artery (CA) and femoral artery (FA) from patients with STEMI while undergoing primary percutaneous angioplasty, were incubated in duplicates (with and without dithiothreitol) with a panel of HLA typed peripheral blood mononuclear cells from 10 healthy volunteers along with rabbit complement for 2 hours. The ensuing cytotoxicity was assesed by: (1)Modified microcytotoxicity assay, assassing cell lysis by viability staining using the combination of fluorescent stains ethidium bromide and acridine orange. (2) Flow cytometry using cell apoptosis/necrosis staining with Annexin V and Propidium Iodide.
Result: The microcytotoxicity assay revealed the presence of IgM non-HLA antibody capable of producing complement dependent cytotoxicity in the serum 11.1% of CA and 3.5% of FA. The flow cytometric assay showed a mean of 9.4% of leukocytes incubated with CA vs 5.9 % with FA were positive for the apoptosis marker Annexin V (p<0.001). Conversely, 81.6 % versus 85.0 %, p=0.012 of the cells incubated with CA and FA were viable (Annexin V− and Propidium Iodide−). There was no difference in cell necrosis (Annexin V+ and Propidium Iodide+) between the two groups (4. 3% versus 3.8%, p=ns).
Conclusion: Reactive non-HLA IgM antibody, capable of inducing complement dependent cytotoxicity and apoptosis was observed more frequently in intracoronary sera at culprit site of thrombotic occlusion of patients with STEMI than the sera derived from peripheral circulating blood. This may have significant implications for clinical outcome in STEMI as the IgM can potentially activate complement and contribute to ischemia-reperfusion injury.