2023-12-23 11:00:32
In the newspapers, on the radio, on TV, on the internet or on social networks… Never have we wondered so much regarding the immune system: how is it formed, how does it work? Why does it have an important role? Expert answers.
What is the immune system? How does he act?
The immune system is a surveillance and defense system which operates continuously to protect our body from external attacks.
How does it work ?
A microbe enters the body through the nose, eyes or mouth, for example in the case of Covid-19; by blood, semen or vaginal secretions in the case of the hepatitis B virus. White blood cells detect and capture it. These cells (leukocytes) are present in the blood, lymph or organs (dermis, lungs, intestines, etc.).
How do cells act?
Immune cells secrete chemicals (cytokines) which recruit others, capable of eliminating the microbe by absorbing and digesting it. This is the stage of acute inflammation responsible for the symptoms: redness, fever, etc.
Who produces the antibodies?
At the same time, other cells migrate via the blood to the nearest lymph nodes. There, they present a microbe fragment, the antigen, to another category of white blood cells, the T and B lymphocytes which activate and multiply. B lymphocytes produce antibodies that can neutralize the microbe, T lymphocytes destroy infected cells.
The antigen of the microbe can be stored in memory
After healing, T and B lymphocytes, located in the lymph nodes, can keep the microbe’s antigen in memory. In this case, you cannot be sick a second time. It is immune memory, which is the basis of vaccination.
Innate or acquired (adaptive) immunity and humoral or cellular immune response
It exists two main types of immunity :
Innate or natural immunity that everyone has from birth; Acquired immunity or adaptive immunity that we acquire through contact with pathogens. This acquired immunity then leads to two types of immune response: humoral immunity and cellular immunity.
What are the main organs of the immune system?
Lymph nodes: located in the neck, armpits, intestine, groin folds, knees, they store lymphocytes. The body has around 100;Le thymus : the T lymphocytes complete their maturation there. Those who are competent (5%) will be released into blood;In installments: it is a reservoir of white blood cells;Mucous : nose, bronchi, intestine, urinary and genital tracts. 20% of white blood cells reside in the intestine alone;Bone marrow : All white blood cells are produced there. B lymphocytes develop there until they mature.
How is our immune system formed?
During pregnancythe mother’s antibodies are transmitted to the fetus via the placenta;At birth, exposure to numerous microbes builds the newborn’s immune system. During childbirth, he comes into contact with maternal vaginal bacteria which will populate his intestine and initiate the development of his microbiota, which plays a key role in the formation of the immune system;Breast milk provides antibodies and contains bacteria which enrich the baby’s microbiota;Vaccinations stimulate the maturing immune system;Food diversification enriches the intestinal microbiota and a strong immune reaction occurs;During community lifethe child encounters new microbes and bacteria, which contribute to the maturation of his immune system.
Did you know ?
1 million : it is the number of elements foreign to the body (bacteria, viruses, parasites, chemical substances, etc.) to which our immune system can respond at the same time;100 millions : it is the minimum number of antibodies present in the body;15 billion: This is the number of white blood cells that the bone marrow produces each day.
Do we always produce antibodies in the event of infection?
Unless there is an immune deficiency, the answer is yes: each time the body encounters an element that is foreign to it, it produces antibodies, recalls Professor of Immunology Éric Vivier. And this, whether you have symptoms or not.
Whatever the disease, this quantity depends on the quantity of viruses that infect usof our individual capacity to produce theme and the nature of the microbial agent himself.
Do they necessarily protect us once morest illness?
Not always. “In the case of AIDS, for example, we produce antibodies but these generally fail to prevent the virus from penetrating cells and spreading,” points out Professor Vivier. For Lyme disease, antibodies provide imperfect and limited protection over time, which is why you can catch it once more.
Regarding Covid-19, there are still a lot of uncertainties. “That said, studies show that infected people produce neutralizing, i.e. protective, antibodies, even when they have developed minor symptoms.” As for the flu virus, its ability to mutate explains why the antibodies produced one year are no longer effective the next.
Infection or vaccination: is the immune defense reaction the same?
In both cases, the mechanisms are the same since the immune system reacts each time by manufacturing specific antibodies once morest the microbe, specifies Professor of Immunology Renato Monteiro. The big difference is that, for the vaccine, we inoculate a fragment of a microbe (dead) or a living microbe but whose virulence has been weakened.
How long are we protected once morest a virus?
© *Thanks to Professor Astrid Vabret (head of the virology department at Caen University Hospital), Professor Odile Launay (infectious disease specialist, coordinator of the Cochin-Pasteur Clinical Investigation Center) and Dr Marie Lachâtre (doctor delegate to the CIC Cochin-Pasteur).
How long are we protected once morest bacteria?
© *Thanks to Professor Astrid Vabret (head of the virology department at Caen University Hospital), Professor Odile Launay (infectious disease specialist, coordinator of the Cochin-Pasteur Clinical Investigation Center) and Dr Marie Lachâtre (doctor delegate to the CIC Cochin-Pasteur).
Why do certain microbes persist in the body despite the immune system?
” Because’they can hide in certain cells, and remain invisible to the immune system for months or years,” indicates Professor Vivier. For example, the herpes virus which can, thanks to a drop in immune defenses linked for example to chronic sleep debt, stress, etc. leave the nerve ganglia where it was “sleeping” and reach the lips. to infect local cells.
Another example, chickenpox: once contracted, the virus persists throughout life in certain lymph nodes, and can reactivate if our immune defenses are weakened, but this time in the form of shingles, says Professor Astrid Vabret, head of the virology department. at the Caen University Hospital.
Immunity and Covid-19
As for the roller coaster Covid-19, researchers do not yet know how to explain it. Once cured of Covid-19, are we still contagious? According to the High Council of Public Health, viruses can still be excreted 48 hours following the end of symptoms. ” But we are not sure if it is still infectious”, points out Father Vabret. “Most studies show that in this case, the virus is no longer capable of multiplying in cell cultures, which is an indirect argument that goes in the direction of non-contagiousness.”
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