Cytokine storm


A cytokine storm, also called cytokine storm syndrome or hypercytokinemia, is a physiological reaction in humans and other animals in which the innate immune system causes an uncontrolled and excessive release of pro-inflammatory signaling molecules called cytokines. Normally, cytokines are part of the body's immune response to infection, but their sudden release in large quantities can cause multisystem organ failure and death. Cytokine storms can be caused by a number of infectious and non-infectious etiologies, especially viral respiratory infections such as H5N1 influenza, SARS-CoV-1, and SARS-CoV-2. Other causative agents include the Epstein-Barr virus, cytomegalovirus, and group A streptococcus, and non-infectious conditions such as graft-versus-host disease.

Cytokine storms versus cytokine release syndrome

The term "cytokine storm" is often loosely used interchangeably with cytokine release syndrome but is more precisely a differentiable syndrome that may represent a severe episode of cytokine release syndrome or a component of another disease entity, such as macrophage activation syndrome. When occurring as a result of a therapy, CRS symptoms may be delayed until days or weeks after treatment. Immediate-onset CRS appears to be a cytokine storm.

Cause

Nutritional deficiency

decreases inflammatory cytokine production by modulation of the immune system.
Nicotinamide is a potent inhibitor of proinflammatory cytokines.

History

The first reference to the term cytokine storm in the published medical literature appears to be by Ferrara et al. in 1993 in a discussion of graft vs. host disease; a condition in which the role of excessive and self-perpetuating cytokine release had already been under discussion for many years. The term next appeared in a discussion of pancreatitis in 2002, and in 2003 it was first used in reference to a reaction to an infection.
It is believed that cytokine storms were responsible for the disproportionate number of healthy young adult deaths during the 1918 influenza pandemic, which killed 50 to 100 million people. In this case, a healthy immune system may have been a liability rather than an asset. Preliminary research results from Taiwan also indicated this as the probable reason for many deaths during the SARS epidemic in 2003. Human deaths from the bird flu H5N1 usually involve cytokine storms as well. Cytokine storm has also been implicated in hantavirus pulmonary syndrome.
In 2006, a study at Northwick Park Hospital in England resulted in all 6 of the volunteers given the drug theralizumab becoming critically ill, with multiple organ failure, high fever, and a systemic inflammatory response. Parexel, a company conducting trials for pharmaceutical companies, in one of its documents, wrote about the trial and said theralizumab could cause a cytokine storm—the dangerous reaction the men experienced.
During the COVID-19 pandemic, many deaths were attributable to cytokine storms.