How does the new coronavirus infect human body？
Earlier we mentioned the strategies used by the new coronavirus to fight the human immune system.
For details, please see: How does the new coronavirus deal with human immune system?
When we sort out these strategies and explain how the human body is infected by the new coronavirus, we will understand why human beings are so vulnerable when faced with the virus of this century.
Let’s look at how the new coronavirus infects the human body.
【The first step of infection – Camouflage】
First, the new coronavirus weakens itself into a “weakly antigenic” invader. The human immune system, when the new coronavirus invades, often treats these viruses as part of normal cells in the body instead of generating an immune response, allowing the virus to proliferate in a large amount in the body. As a result, although the new coronavirus cannot harm human life immediately, it has a long asymptomatic incubation period. At the same time, this “weak antigenicity” will make subsequent “vaccines” unable to achieve strong or long-lasting effects, making humans hate them but helpless.
【The second step of infection – Cause an innate immune response disorder – Severe inflammation】
95% of the human innate immune system will perform the correct function to eliminate the invading new coronavirus and make the virus incapable of attack (activity). However, about 5% of the innate immune response will be abnormal, and the fine-regulated signal transmission process goes wrong, causing the innate immune cells to produce too much cytokine, generating “similar but not completely” cytokines storm. The actual effect of this “cytokine storm” is that the new coronavirus knows that when the innate immune system detects its invasion, it will produce a cytokine called “interferon” to prevent the replication of the virus, this is the first line of defense of the immune system. The massive production of this type I interferon can control the number of viruses and prevent the appearance of mild symptoms.
However, for 5% of the elderly, or patients who have been exposed to certain viruses for a long time, the immune system in the body is not sufficiently sensitive to these “weakly antigenic” new coronaviruses, so the innate immune system starts reacting when the virus has been replicated for a very large amount. The excessive response of interferon produced by a large number of viruses triggers over production of inflammatory cytokines (new coronavirus is generated by the bradykinin storm caused by excessive inflammatory cytokines), causing severe inflammatory reactions and symptoms.
In addition, the new coronavirus may also weaken the immune system’s ability to produce interferon, and may even cause the immune system to produce “type I interferon antibodies”. Although these phenomena are still in the research stage and the cause cannot be determined, from the general phenomenon of human society, it is very likely that the “weekly antigenic” new coronavirus “disguises” as its own “antibody” (that is, the receptor that can eliminate the new coronavirus), so that the production of the antibody cells that can really eliminate the virus or the interferon that can prevent virus replication can be restrained. The weakly antigenic virus mixes into the environment of interferon and antibodies to destroy it, causing bad money to drive out good, and create a better environment for virus survival.
Get to the bottom of it, all the problems at this stage are due to the slow response of the innate immune system and the inability to perform a non-specific immune response to invasion of “weakly pathogenic” viruses at the very start.
【The third step of infection – Neutrophil overreaction】
In addition to severe inflammation, the symptoms of the new coronavirus infection may also be caused by the delayed innate immune response that makes a large number of viruses replicated, and triggering a large number of proliferation of neutrophils (a type of white blood cell) that destroys pathogens. The extracellular network structure (consisting of DNA, antimicrobial proteins, and enzymes) that discharges neutrophils is in the process of eliminating viruses and other pathogens, and it will also destroy tissues and thrombus caused by destroying anticoagulant proteins, damage lung cells and cause severe illness. The reason for this phenomenon is still that the innate immune system reacts too slow. When the amount of virus is too much, it starts to react and initiate the immune response of the neutrophil, which can also cause anticoagulant function lesions and severe death.
【The fourth step of infection – Block the production of T cells】
The excessive inflammatory reaction produced in the second step has caused a large number of severe patients and deaths of new coronary pneumonia around the world. Most of these are caused by abnormal reactions of innate immunity. The adaptability of the human lymphatic system (acquired specificity), when T cells (secreted by the thymus) and B cells (secreted by the bone marrow) in the immune system are formed in sufficient numbers, the human body will have a longer-term immunity to the invading new coronavirus because of the production of these antibody cells. This is the theory of immunology. For the new coronavirus, what kind of strategy does it have to deal with the antiviral mechanisms of the human body’s acquired specific immune system?
When memory T cells are stimulated by virus antigens, they store specific information. After receiving the same stimulation, they can differentiate into T cells that candela with the same bacteria, viruses and cancer cells.
This T cell has a CD8 logo on its surface, it functions like a killer or cytotoxic, identifying and destroying infected cells. After binding to the infected cells, the cytotoxic T cells release toxins and cause the infected cells to die.
When B cells are stimulated, they are divided into “plasma cells” and “memory B cells”.
(B cells do not have the ability to attack infected cells and can only produce antibodies)
Plasma cells are the human body’s factory for producing antibodies. They can produce antibodies to label foreign invaders and help killer T cells to identify invaders.
It can remember the invading antigen. If it receives the same antigen again, it will quickly produce new plasma cells and new memory cells. The plasma cells will again produce antibodies to destroy the antigen.
The number of two kinds of T cells (memory and cytotoxic T cells) in the blood of many severe patients with new coronavirus is very small. This abnormal response of the acquired adaptive immune system has confused many researchers, especially in the cells collected from the lungs of severe patients, which is the invasion spot of coronavirus, through single-cell sequencing technology, a very large number of T cells were found in the several types of immune cells. This phenomenon of T cells, which only disappear in the blood, has attracted a lot of attention.
Some studies suggest that he reasons may be:
However, we still have doubts about whether the “weak pathogenicity” of the new coronavirus allows the initial “cytokine production” to directly affect the production of T cells. That is to say, there may not be enough T cell proliferation in the bone marrow.
These hypotheses and verifications will have an important impact on T cell therapy.