The human immune system is complicated, but you have probably heard of lymph, white blood cells, and killer T cells. However, have you heard of cytokines?
Cytokines are protein signaling molecules, or ligands, involved in the inflammatory response. This means that when you get hurt or infected by a pathogen, cytokines are released by activated macrophages or neutrophils—pathogen-eating immune cells. The cytokines work to draw blood to the area, which brings other agents of the immune system to suppress the injury or infection.
Cytokines typically function in a positive feedback loop: when one immune cell releases cytokines, these cytokines bind to other immune cells, triggering the production and release of more cytokines. This inflammatory response can be local, if the infection or the injury is minor, but a severe problem can cause a systemic response throughout the whole body.
Cytokines have been receiving a lot of attention lately for their role in patients’ responses to COVID-19 infections.
In the case of infection by COVID-19, cytokine response can cause an overreaction of the immune system. Activated macrophages and neutrophils, which are meant to consume pathogens and damaged cells, may begin attacking healthy cells. This is called a cytokine storm, or cytokine storm syndrome, and can be fatal, regardless of the patient’s age or health condition before contracting COVID-19.
With the increased blood flow to the area of infection—the lungs, in the case of COVID-19—come increased chances of blood clotting. Clotting in the lungs leads to difficulty breathing, and blood clots can also form in the brain or in other parts of the body, as well, due to the cytokine storm creating a hyperactive immune system throughout the body. This can cause multiple-organ failure or multi-organ dysfunction syndrome (MODS).
Cytokine storms do not happen to everyone and it is still unclear why, but cytokine storms have a very high mortality rate when they do occur. Unfortunately, differentiating between a patient suffering from just COVID-19 and a patient suffering from a COVID-19-induced cytokine storm can be a complex process. There are multiple tests to determine if a patient is experiencing cytokine storm syndrome, including blood tests, but what can be done to help patients that are experiencing a cytokine storm?
Potential treatments to tamp down cytokine storms exist, especially treatments used for other conditions that sometimes involve a hyperactive inflammatory response, such as rheumatoid arthritis or an H1N1 infection—also known as swine flu. However, the potential consequences of turning off a patients’ immune system while they are battling a novel coronavirus infection could be too dangerous. Clinical trials have yet to provide an answer.
So, the next time you tell yourself that your immune system should be able to protect you from the coronavirus, consider the possibility that your immune system may be too strong for your own good.
