The immune system is saddled with the responsibility of helping us fight and fend off diseases and their causative agents. As man’s surveillance system, it possesses inbuilt mechanisms for distinguishing ‘self’ (what belongs to him and is considered safe) from ‘non-self’ (what is not his or considered unsafe). Working through a network of specialty cells (killer and helper T-cells), antibodies (A, D, E G, and M), and other agents, the immune system is able to rid the body of bacteria, viruses, protozoa, toxins, and cancerous cells.
It does this by eliciting an ‘immune response’. In an immune response, the immune system works through its network of antibodies and T-cells. It targets and detoxifies, or otherwise, destroys such ‘non-self’ molecules, technically known as ‘antigens’.
Ideally, this process is highly coordinated and exhibits a degree of specificity. But, this is not always the case.
Sometimes, the immune system acts differently. It may react abnormally to foreign substances, and in the process attack the cells of its host. Allergies and autoimmune diseases are the results of such abnormal reactions of the immune system.
In allergies, the immune system overreacts or responds excessively to a foreign, sometimes ‘safe’ substance. People may be allergic to certain foods (milk, eggs, nuts, fish, wheat), drugs (penicillin), insects (bites and stings), or pets (cats).
Autoimmune diseases involve a direct attack on, and destruction of cells of the body. It is a misdirected immune response. If you have ever got so angry at something or someone that you end up hurting yourself in the process, then you would understand this anomaly. Rheumatoid arthritis, insulin-dependent (juvenile) diabetes (type 1), inflammatory bowel disease, and lupus are common autoimmune diseases.
This abnormality in the immune response that gives rise to allergies and autoimmune diseases has also been observed in SARS-CoV-2 and COVID-19. Scientists believe that most of the complications arising from COVID-19, including the severe damage to the lungs, as well as other organs, result from exaggerated immune responses.
One of such reactions has been termed a ‘cytokine storm’.
Cytokine storm is a term coined to describe overreactions from the immune system that are often detrimental to an individual. It is implicated as a common cause of severe organ damage and death in COVID-19 patients.
Cytokines include interferons, interleukins, and growth factors that are produced by different cells in the body including neutrophils, a type of white blood cells. They aid in eliciting a coherent immune response.
In a recent review article, titled, ‘Targeting potential drivers of COVID-19: Neutrophil extracellular traps’, published in the Journal of Experimental Medicine, ‘neutrophil extracellular traps’ (NET) are suggested to be the likely culprit in cytokine storms. NETs are networks of DNA gauze containing toxic enzymes, which kill pathogens. They are produced by neutrophils, which the researchers suggest to be playing a role in the initiation and propagation of cytokine storms. The Acute Respiratory Distress Syndrome (ARDS), pulmonary inflammation, mucous secretions in the airways, extensive lung damage, and blood clots which often characterise severe COVID-19 cases have been linked to NETs.
Some of the drugs currently being targeted at SARS-CoV-2, act by lowering the severity of immune responses against the virus. Tocilizumab, Sarilumab, and Ruxolitinib are examples of such immunomodulatory drugs.
