FCGR3A and heart failure: The expression of proteins involved in Ig-mediated immune activation [e.g., Fc Gamma Receptor IIIa FCGR3A], proteins associated with heart failure [e.g., Tenascin C (TNC), Quiescin sulfhydryl oxidase 1 (QSOX1)], was enhanced in severe MIS-C compared to KD [39].