How do children resist Covid-19?

How children fight COVID-19 ؟

Children have largely avoided severe symptoms of COVID-19 because they have a strong initial “innate” immune response that quickly eliminates the virus. But researchers from the “Garvan Institute for Medical Research” discovered that, unlike adults, children’s immune systems do not remember the SARS-CoV-2 virus, that is, they do not develop an adaptive memory to protect against infection with it, so when they are later exposed to the virus, the child’s body deals with it as a new threat, according to As published by News Medical, quoting Clinical Immunology.

The “naivety” of the immune system

The reason is that “the children have not been exposed to many viruses, so their immune systems are still “naive.” Because children do not develop memory T cells, they are at risk of getting the disease again.

Professor Fan points out that with each new infectious episode as a child gets older, there is a risk that their T-cells will become 'exhausted' and ineffective, like the T-cells of the elderly, which is why it is important to vaccinate children.

The immune system has two modes, with the innate immune system being the first line of defense, consisting of physical barriers such as skin and mucous surfaces that prevent viruses from entering. It consists of cells that make chemicals to send signals to other cells and ward off viruses. But the innate immune system does not distinguish between one type of virus or another.

The second line of defense consists of the B and T cells of the adaptive immune system. These cells contain specific receptors that can recognize and mark different parts of the virus and generate a rapid response to neutralize or reduce them.

Researchers have found that infants' immune systems are like a "blank slate" with a much higher percentage of naïve T cells. As they move through childhood into adulthood and are exposed to more viruses, their naïve T cells are replaced by memory T cells that are able to respond to viruses they have seen before.

Associate Professor Philip Britton, pediatric infectious disease physician at Westmead Children's Hospital, explains: "Children's immune systems go from relying mostly on the innate system, to needing the adaptive system as a backup as they get older and are therefore unable to clear viruses. Quickly".

problem in the elderly

Interestingly, the results of the study indicate that the cause of the elderly infection is a kind of excessive immune reaction to the SARS-CoV-2 virus, as Professor Fan says that “when adults are first infected with the SARS-CoV-2 virus, their memory T cells recognize Just on what they've seen before, for example, a familiar part of the coronavirus co-existing with common cold viruses," he said, explaining that it may be because the immune system "locks up a misdirected response that's not specific to SARS-CoV-2, causing It provides an opportunity for the virus to escape and multiply unchecked to cause more severe symptoms while the immune system ramps up to try to fix the problem.”

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