IMMUNE RESPONSE TO COVID – 19 PANDEMIC
HOW DOES OUR IMMUNE SYSTEM WORK?
WHAT IS “HERD – IMMUNITY”?
“Science knows no country, because knowledge belong to humanity, and is the torch which illuminates the world.” - Louis Pasteur
Thanks to our immune system, which has been evolving over many millenniums, we are able to live in an ocean of microorganism (bacteria, viruses, fungus, parasites), called microbiome or microbiota. They are in the air that we breathe, they live on our skin, in our body’s cavities and hallow organs. We share many of their genes in our genomeand they perform many beneficial tasks for our body. They prime our body’s immune defenses and protect us against invading pathogenic microorganisms. Our life is not possible without them.
Viruses are no strangers to our genes or immune system. Viruses are extremely small microorganisms (1/1000 the caliber of a strand of human hair) that contain a tiny piece of genetic material (RNA or DNA), packaged in lipo- protein capsids. Viruses do not have the ability to synthetize proteins on their own. They hijack other living cells for protein synthesis, for extra lipids and nucleotides to survive and to replicate. Viruses are the most devious pathogens to invade the immune responses’ of their host.They could bypass the anatomical barriers of the skin by insect bites or enter our respiratory tract through openings like nose, mouth or eyes.
COVID – 19 Coronavirus could infect not only with direct contact, but also with the cough or sneeze of an infected person that can float in the air like dust particles for hours. The virus enters our respiratory tract when we breathe air and attaches itself with its corona spikes to the respiratory mucosal cells receptors and easily enters inside the cells. That is why using a facemask is so important. Once inside the cell, Coronavirus uses the genetic materials of the host cell to produce a special protein to keep host’s immune defenses at bay. The virus then starts using other necessary materials in the host cell to rapidly clone itself and replicate. These activities do not go unnoticed by the immune system.
I am not an immunologist but I think we need a short summary of basic principles and the working anatomy of the immune system to better understand the topic and to appreciate the beauty and the complexity of our immune system.
Our immune system is made of two different protective immune mechanisms:
1. Innate ( Natural, Nonspecific ) Immune Mechanism
2. Adaptive ( Acquired, Specific ) Immune Mechanism
Innate Immune Mechanisms are provided by anatomical barriers like multilayered, keratinized, difficult to penetrate skin; Mucus layers on the mucosal surfaces to trap microorganisms or foreign particles; cilia on the respiratory tract mucosa to expel trapped particles; hair in our nostrils; strong gastric acid production are all the parts of innate defense mechanisms. If any microorganism breaches these defensive barriers, they are met with body’s defensive cells like phagocytes, killer cells or granulocytes. These cells besides killing invading microorganisms, also notify the more powerful Adaptive Immune System for help.
Adaptive Immune System actions are pathogen specific and it takes longer (5-to 7 days) to develop. It is carried out by the immunocompetent lymphocytes: T and B lymphocytes. These cells are activated only after the specialized antigen presenting cells (APC), present them a crucial piece of invading organism’s protein (antigen or Ag). They then multiply as specifically armed cells to fight the infection. T- lymphocytes are cytotoxic and kill invading microorganisms directly, while B- lymphocytes (Plasma cells) produce neutralizing antibodies to kill pathogens and produce a lasting immunityagainst them.
Herd immunity is an epidemiological conceptthat if enough people get infected with the virus and survive (80% of Coronavirus patients survive), they become immune. Eventually more and more people become immune and the outbreak would fizzle. Herd immunity also could be achieved by vaccination. Herd immunity could very well work for poor countries against COVID – 19 pandemic if the people who die from this virus are considered the unavoidable collateral damage in a war.
