P2RX7 and COVID-19: For example, when the half-maximal effective concentration of the P2X7 receptor antagonist lidocaine needed to block hyperinflammation was excessive, adverse reactions were minimized by selectively inhibiting P2X7 receptors of the immune cells of the lymphatic system, by inducing clonal expansion of Tregs in local lymph nodes that subsequently migrated to impart systemic anti-inflammatory activity, notably improving outcomes in six critically ill COVID-19 patients (201).