Covid-19: How our immune system works and how it fights against coronavirus

Without specific treatment or drugs, and without a vaccine on the near horizon, the only defense that our body has against the new coronavirus is the immune system.


How body immune responds to coronavirus infection will largely depend on the results: we may suffer from mild symptoms such as dry cough, sore throat, tiredness and fever, severe symptoms such as pneumonia and acute respiratory problems, to multi-organ failure and death. Without specific treatment or drugs, and without a vaccine on the near horizon, the only defense that our body has against the new coronavirus is the immune system.
Covid-19: How our immune system works and how it fights the coronavirus
How body immune responds to coronavirus infection will largely depend on the results: we may suffer from mild symptoms such as dry cough, sore throat, tiredness and fever, severe symptoms such as pneumonia and acute respiratory problems, to multi-organ failure and death.
Experts have explained in numerous articles how to strengthen this system to better deal with this disease. They recommend following a healthy diet, getting more sleep, avoiding stress, excessive alcohol, tobacco and other toxic substances.
But before looking at these recommendations, let's start by understanding how the immune system works and how it activates when it comes in contact with the coronavirus.

A hostile world

Talking about how body immune respond to covid-19 infection; the immune system is a complex network of cells, organs and tissues that work together to defend ourselves against the microorganisms and toxic substances that could make us sick - fungi, parasites, viruses and bacteria - and that are present in the world around us.
All our organs contain cells of the immune system and these are also in the blood (in the leukocytes, which are the white blood cells) and in the lymph (the clear liquid that runs through the lymphatic vessels).
All our organs contain cells of the immune system and these are also in the blood, lymph and lymph
And although immune cells originate in the bone marrow and there are places where they are more concentrated, such as the lymph nodes, tonsils, spleen or thymus, we can find them in the skin, mucosa, lungs, digestive system and every corner of the body.
When our body is confronted with a pathogen (a microorganism capable of causing disease, such as the coronavirus), the immune system responds to covid-19 in two ways in parallel.
One is the so-called innate response. It is the first to be developed and is normally effective in eliminating different types of aggressors.
That is "the first thing we see when we see a disease," explains Dr. Silvia Bucciarelli, who worked for years as a specialist at the Hospital Clinic in Barcelona and now coordinates the NGO PINEAS (Integrated Program of Immunology and Autoimmune Diseases).
This response increases blood flow to the infected area, and so "this part of the body turns red and hot by the same mechanism," he says.
"Cells and certain substances - like proteins and cytokines - come out of the blood vessels that try to stop the infection," he adds.
The other is the adaptive response to coronavirus, which produces antibodies or specific cells capable of destroying certain microorganisms or infected cells.
This response can take four to seven days to arrive, "so the innate response has to try to maintain the front line, until the specific immune response to the virus develops," the expert continues.
"It is like a missile that is aimed at one particular organism and not another."
A particular feature of the adaptive response is that it leaves memory. That is, remember the pathogens with which your body has come into contact in the past, and therefore you will know how to combat them in the future.
This means that, in theory, if we were once infected with covid-19, we could not get a second one.
Although being a new virus, of which there are still many questions to answer, it is not completely clear if Coronavirus generates immunity and, if it does, for how long it lasts.
As we mentioned before, both immune responses work in teams, where the innate acts as a guide for the adaptive response: it communicates through cells what type of microorganism is infecting us and where in the body it is found.
Thus, the immune response is directed to the place where the infection is, and not to other places where we do not need it.

And the coronavirus?

To begin with, it must be borne in mind that since it is a new virus, much of what is inferred from the immune response to covid-19 (its official name is SARS-CoV-2, but the WHO accepts that we call it with the very name of the disease it causes, covid-19), is based on the similarities with its "cousins" SARS (Severe Acute Respiratory Syndrome) and MERS (Middle East Respiratory Syndrome).
According to Bucciarelli, "the immune system against viruses has two main objectives: one is to try to neutralize them and prevent them from entering the cells ."
"The other one, if the virus managed to break through that barrier and penetrate the cell, is to destroy that infected cell by a mechanism known as apoptosis, which is programmed cell death."
Recall at this point that this coronavirus, like all viruses, cannot reproduce unless it enters our cells and hijacks its mechanism to replicate.
And, as it is primarily a respiratory virus, it begins by infecting the throat, before continuing its journey through the bronchial tubes and reaching the lungs.
However, viruses are very cunning and can trick the immune system into not knowing that they are there.
One way that covid-19 appears to outwit the immune system is by inhibiting the production of interferon, a protein that cells of innate immunity produce when our body comes in contact with a virus, with the intention of preventing it from getting into the cell.
WHO says a vaccine will be ready between April and June 2021.
But, as Bucciarelli explains, "apparently, covid-19 can interfere in the production of interferon, as well as prevent interferon from fulfilling its function, and therefore the virus could enter the host cell" .
In addition, he adds, it could be interfering with another mechanism: the one that allows the adaptive immune response to produce antibodies against that specific virus.

Response according to damage

In 80% of cases, the immune system's response to the coronavirus is effective, which is why people are asymptomatic or suffer mild symptoms.
In the remaining 20%, no: the virus enters the cells because the immune system could not block it.
So, these cells where the virus reproduced are destroyed and die in an uncontrolled way.
"By destroying those cells, the immune system detects that there is cellular damage, and there a type of cell that stimulates an inflammatory response is stimulated to prevent that process," says Bucciarelli.
It is this response that can complicate the picture.
"That increased influx of cells causes widespread inflammation of the entire lung, or it can go further and prepare the entire body to defend itself. And this can lead to shock as a consequence."
According to Margarita del Val, an expert in viral immunology at the Severo Ochoa Center for Molecular Biology in Madrid, Spain, "the problem is that in the final stages, not only the amount of virus produced is out of control, but also the amount of cytokines, or the mediators who are building powerful inflammation so that the battle is very soft. "
"And this also ends up damaging the infected person."
But this is not really an exaggerated response, Bucciarelli says, but "proportional to the damage the infection is causing."
"It can give mild or severe symptoms. And this depends on the characteristics of the infecting microorganism, which can be very aggressive, on the characteristics of the host and on the environmental characteristics."

How to optimize the immune system against covid-19

Since the first thing that reacts to the virus is our innate immune response, it is important to have a competent immune system to fight battle with it.

A healthy diet is essential to have an optimal immune system against coronavirus.

For its structure to be adequate, a varied diet is essential, but also exercise, rest and avoid stressful situations.
"It is important to do moderate exercise every day and not extreme, because that leaves us exhausted and without resources to the immune system," says Del Val.
On the other hand, it is important not to drink excessively and avoid tobacco.
"Tobacco alters cells of the respiratory tract. Those cells of the initial respiratory system lose their shape and the function of the cells that line the lung is also altered," Bucciarelli explains.
So, a person who smokes is highly susceptible to more serious infections.
Psychic factors such as loss of weight, anguish, and chronic stress also affect the functioning of the immune system against covid-19.
In short, all these recommendations, says Del Val, "will help us to have a well-regulated system: not too weak, not too strong, but reacting to the extent of the aggression we suffer."
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