A cytokine storm in severe COVID-19 involves hyper-activation of the immune system and hyper-coagulation, leading to shock, respiratory distress, and multi-organ inflammation.

“A: Cytokines are small proteins secreted by immune cells that have an effect on other cells. Examples are interferons (IFNs), TNFalpha, interleukins (IL1,6), and transforming growth factors (TGFs). During the course of COVID-19, some patients bring down viral numbers only to rapidly descend into a state of shock involving hyper-activation of the immune system and hyper-coagulation in small blood vessels. This rapid and uncontrolled inflammatory signaling cascade, known as a “cytokine storm,” exacerbates the heavy breathing and low oxygenation, and triggers inflammation in major tissues such as the lungs, kidneys, heart, liver and brain. The resulting vascular inflammation is emerging as a main cause of complement-associated microvascular injury and thrombosis in severe COVID-19 cases.”