P2RX4 and COVID-19–associated multisystem inflammatory syndrome in children: More importantly, the most autoreactive antibodies in PIMS-TS patients are directed against antigens of organs important in PIMS-TS pathology such as the endothelium of the heart (P2RX4, ECE1 and MMP14), the gastrointestinal tract (MUC15, TSPAN13 and SH3BP1) and immune cell receptors (CD244, IL-1A, IFNGR2, IL-6R and LAMP1) [11].