Figure 3.

Involvement of multiple systems in COVID-19. Activation of the immune system following the entry into the respiratory system involves activation of neutrophils and monocytes with release of the MPO and ROS, which cause damage to both, local (alveoli and lung parenchyma) as well as distant tissues including gastrointestinal tract and liver, kidneys, brain, peripheral circulation and the heart. Damage to these tissues manifest as organ dysfunction and multi-system failure. Release of heme degradation products and iron along with ROS are particularly damaging to the kidneys, liver, heart, and brain, while inappropriate activation of the coagulation system and insufficiency of NO can result in pulmonary and peripheral vasoconstriction. Simultaneous occurrence of these events can result in severe, persistent, and potentially fatal hypoxemia.