A human-on-human assay for detecting anti-myocardial antibodies in patients with myocardial disease.

Adaptive immune responses, particularly the production of anti-myocardial antibodies, have been implicated as critical mediators in myocardial healing and remodeling following myocardial infarction (MI), acute myocarditis (Myo), and heart failure (HF). However, current methods for detecting heart-reactive antibodies in patients are insufficient, as most rely on heart tissue slices from primates or other species. These approaches pose technical, logistical, and ethical challenges, including the risk of false negative results due to lack of inter-species cross-reactivity. To address these limitations, we developed a human cell-based assay to screen for patient-derived serum or plasma reactivity against human cardiomyocytes differentiated from induced pluripotent stem cells (iPSC-CMs). This human-on-human test system can detect cardiomyocyte-specific immunoglobulins present in patient plasma by applying indirect immunofluorescence staining, followed by convenient visualization through either confocal microscopy or standard widefield systems available in clinical laboratories. Overall, this approach provides a physiologically relevant and ethically responsible model for rapid, accurate testing of anti-myocardial antibodies across various clinical settings, thus offering accessible tools to stratify patients with myocardial disease according to their adaptive immune response status.