The immune system uses a special mechanism to protect children from the new virus-it usually protects them from the severe effects of COVID-19 in two different ways.The immune system in their respiratory mucosa is Much more active than adultsIn children, the system responds much faster to viruses that have never been encountered before, such as pandemic pathogens. At least, this is what a recent study by Irina Lehmann and colleagues of the Charité Berlin Institute of Health showed.
The researchers examined the differences in mucosal cell types between children and adolescents.As the team reported Natural biotechnology, Children not only have more immune cells in their mucous membranes; they can also produce type I interferon faster, which is essential for fighting the virus. Therefore, these key molecules can also prevent immune system disorders in many severe COVID-19 cases.
Faster virus fighter
“The defense against viruses works on two levels. First, you can obtain an antiviral response in the cell through the receptor, such as inducing the production of interferon,” Lehmann explained. “Second floor [is] Immune cells in the tissue, such as activated killer cells and neutrophils. Research conducted by her group showed that these two levels of virus control are on high alert in children. The team analyzed nearly 270,000 cells from swabs collected from the nasal mucosa of people from 4 weeks to 77 years old. Samples. About half of them were infected with SARS-CoV-2, the virus that causes COVID.
The samples also show that children’s cells produce a large number of immune receptors, which can recognize viruses and trigger immune responses. One such receptor molecule, MDA5, is a sensor for foreign RNA found in many viruses, including SARS-CoV-2.It also directs the production of type I interferons Critical to the ability of the innate or fast-reacting immune system to fight the virusThey activate immune cells and put them in a special state of vigilance, making it difficult for viruses to multiply.
“Interferon is extremely effective against viral infections,” explains Marco Binder of the German Cancer Research Center in Heidelberg, who is a co-author of the study. Natural biotechnology Learn. However, as an effective countermeasure, the new coronavirus has its own protein, Prevent the production of interferon“SARS-CoV-2 reproduces very fast in cells, which means that the formation of viral proteins is also very fast,” said Binder, who studies interferon. “And they inhibit the interferon system so significantly that we see little or no interferon production in cell culture when there is an infection.”
The dual role of interferon
In cell cultures of lung epithelial cells, Binder tested whether the large amounts of MDA5 observed in children might retain the interferon response. Adults hardly have these receptors-if an infection occurs, these molecules must be produced from scratch. This will take time, and SARS-CoV-2 uses time to kill the entire immune signal system. Because of the stronger basic activation of MDA5 and similar receptors, children seem to be able to avoid this. In fact, Binder’s experiments show that in children, SARS-CoV-2 is too slow to prevent cells from producing interferon.
Therefore, for severe SARS-CoV-2 course, children actually have double protection. Type I interferon does more than warn the body about the virus. Signal molecules regulate many processes in the general immune response. Studies have shown that if they do not exist during SARS-CoV-2 infection, The body’s defenses are out of step At the worst moment. The spread of the virus can cause tissue damage, which in turn stimulates the immune system to fight pathogens more violently.
However, due to the lack of type I interferon, the defense response is already in a dangerously unbalanced state and exceeds the target. Therefore, even in the severe course of SARS-CoV-2, the immune response can cause massive tissue damage in the lungs.Other research results also indicate the key role of interferon in this process, which leads people to Congenital defects of type I interferon response-Or autoantibodies against these signaling molecules-in response to the high risk of COVID-19 suffering from a very serious disease.
The child will still be seriously ill
Children benefit from the fact that their ultra-sensitive immune system makes the interferon response faster than SARS-CoV-2 prevents it from being produced. “On the contrary, if the concentration of MDA5 increases, you skip the first step where the protein must first be upregulated,” Binder explained. “This is why cells immediately produce measurable interferon when they come into contact with the virus-even before SARS-CoV-2 has a chance to intervene.”
However, if the child’s interferon system is disturbed-for example due to genetic defects-this protective effect will disappear. Binder said this may explain why even some seemingly healthy children and young people still get sick. But the important point is that, generally speaking, children can fight unknown viruses very quickly and effectively.
This effect still exists in the second stage of the immune response, because the necessary immune cells, such as activated killer cells, are already present and ready. One of the main findings of the study by Lehmann and her colleagues is that there are many more of these cells in the mucosa of children than in adults. “The fact that immune cells are already present in the tissues gives you a good start, because all these cells don’t have to be called by signal substances,” Lehman said. “Of course, if the virus reproduces unhindered in the tissues for one day less, the situation will be different.”
Why adults are still not protected
The results of the study show that children’s immune systems are designed to be particularly effective against the virus the first time they encounter it. Experts such as Peter Palese, a flu researcher at the Icahn School of Medicine at Mount Sinai in New York City, did not participate in this work, so it is suspected that children are generally better than adults in a pandemic——Presumably, this effect was observed as early as 1918Adults must rely on the adaptive immune response-the specific protection provided by antibodies and T cells to individual pathogens, which will not develop until a period of time after exposure to the virus.
This proved to be a significant disadvantage in the pandemic. Compared with the seasonal respiratory pathogens that were usually blocked when they were young, adults are particularly powerless against a new virus due to the enhanced immune system. This is evident in COVID-19, which is an almost exponential increase in the elderly population, as evidenced by the rate of serious illness and death.
But why does the only child have such efficient protection? Binder explained that there are several reasons. “If the body keeps activating this [process], Of course, this will cause incredible selection pressure on pathogens,” he said. The virus has long adapted to it. In addition, in the long run, the body cannot afford this system. “In all signaling systems, the interferon response leads to cellular inheritance. The biggest change in activity,” Binder said. If this response continues, it will have a huge impact on cell activity, which will have a huge impact on the entire body.
This is not just a theoretical question. “It is well known that people with over-activation of the congenital interferon system usually suffer from very serious inflammatory diseases,” Binder said. Therefore, the price of the interferon anti-virus super weapon must be carefully kept. As a result, SARS-CoV-2 can dissolve it-not only breaks through this line of protection, but also makes the entire body’s defense system out of control. However, in the first few years of our lives, we actually seem to be one step ahead of the virus.
This article originally appeared in Science spectrum And reprinted with permission.