cytokine-storms

Context

Evidence is emerging regarding cytokine storms in the body and its role in making people succumb to the novel coronavirus including few young ones.  

Few facts related to COVID-19 deaths:

  • Who is more vulnerable? While various studies have shown that the disease has more severe consequences for those above the age of 60 years, and especially those with existing poor health conditions.
  • Mortalities in young people:
    • Some countries have also reported deaths of younger people, after catching the infection.
    • According to a WHO report ,2.5 percent of those under the age of 19 developed severe disease from the coronavirus, and 0.2 per cent were critically ill  as per a sample set data.
  • Critical COVID-19 patients: They are defined by manifestations that include respiratory failure requiring mechanical ventilation and shock or organ failure that requires intensive care, and which may lead to death.

Mechanism of working of immune system

  • The immune systems in our bodies protect us from bacteria, viruses, and parasites by removing them from our systems. 
  • What are antigens? 
    • The immune system gets activated by things that the body does not recognise as its own. These things are called antigens, and include bacteria, fungi and viruses.
  • Inflammation:
    • An effective immune system response involves inflammation, an important and indispensable part of the process. 
    • For example in case of physical injuries the area around injury becomes red and swollen, and the immune system in response deploys white blood cells to the injured area to begin work on repairs. 
    • Without such an immune response, injuries would not heal, and infections would become deadly.
    • Inflammation has an important protective function. The release of inflammatory mediators increases the blood flow to the corresponding area, which allows larger numbers of immune system cells to be carried to the injured tissue, thereby aiding the repairing process.


 

About Cytokine storms

  • A cytokine storm or CSS is characterised by the overproduction of immune cells and the cytokines themselves because of a dysregulation in the immune system process .
    • Cytokines are signalling proteins that are released by cells at local high concentrations.
  • It is an overreaction of the immune systems, which triggers what is known as a “cytokine storm syndrome” (CSS).
  • It is triggered when a virus (or antigen) enters the body for the first time.
  • A cytokine storm can occur due to an infection, auto-immune condition, or other diseases. Signs and symptoms include high fever, inflammation (redness and swelling), severe fatigue, and nausea.
  • Implications:
    • A severe immune reaction, leading to the secretion of too many cytokines in the bloodstream, can be harmful since an excess of immune cells can attack healthy tissue as well.
  • Few diseases in which CSS has been seen are - 
    • Spanish Flu 
    • H1N1 (swine flu) 
    • H5N1 (bird flu) 
  • Cytokine responses against human coronaviruses:
    • SARS-CoV-1 (which caused SARS), SARS-CoV-2 (which is responsible for the current COVID-19 pandemic), and MERS can result in acute lung injury and acute respiratory distress syndrome (ARDS).
  • Correlation with COVID-19:
    • Here a cytokine storm is associated with a surge of activated immune cells into the lungs, which, instead of fighting off the antigen, leads to lung inflammation and fluid build-up, and respiratory distress.
    • If the clinical features of CSS are not recognised and adequate treatment is not promptly instituted, multiple organ failure can result. 
    • Researchers writing in The Lancet recently have suggested that all severe COVID-19 patients should be screened for hyper inflammation.