How the New Coronavirus Bypasses the Body's Immune System?

Zhang Wenhong, a well-known doctor and director of the Shanghai Huashan Hospital Infection Department, once said in an interview that the most effective drug against the new coronavirus is human immunity, so initially, how did the new coronavirus bypass the human immune system What about infections?

The human body has three lines of defense, the first line of defense consisting of skin and mucous membranes and their secretions, the second line of defense consisting of bactericidal substances in body fluids (such as lysozyme) and phagocytic cells, and mainly composed of immune organs and cells The third line of defense. The new coronavirus easily crosses the first line of defense through the mouth, nostrils, and eyes, and crosses the second line of defense with its new and unprecedented features, stimulating the third line of defense, when the third line of defense responds effectively , Successfully infected the body.

How does the new coronavirus bypass the body's immune system to infect?

The structure of coronavirus is as simple as other viruses. Simply put, it is a protein shell wrapped with a piece of genetic material RNA. They cannot metabolize and reproduce independently, and must enter normal cells, just like parasites, using the energy of the infected cells, that is, the host, to survive and reproduce. When a virus infects a cell and multiplies, the corresponding protein or antigen is produced on the surface of the infected cell. The body's immune system finds the antigen and starts a comprehensive defense battle.

The human body has three lines of defense against pathogens. The first line of defense composed of skin and mucous membranes and their secretions, the second line of defense composed of bactericidal substances in body fluids (such as lysozyme) and phagocytic cells, and the third line of defense composed mainly of immune organs and immune cells. The skin and mucous membranes of the human body's first line of defense can block the random invasion of most pathogens. If the new coronavirus wants to enter the human body, it needs to start from the relatively exposed and non-skinned areas, such as the mouth, eyes, and nostrils, which is also the spread of the virus. The main channel.

After being blocked by the skin, the new coronavirus enters the trachea, and the mucosal cells that make up the surface of the tube secrete mucus to encapsulate the virus and are pushed out of the body by the cilia to the larynx or nose. Runny nose. However, most of the symptoms of the new coronavirus Pneumonia are dry cough rather than sputum, which shows that  the New Coronavirus has successfully passed through the trachea cunningly, through the bronchi to reach the alveoli.

The virus enters the alveoli and infects the alveolar cells to begin to multiply. The macrophage of the second line of defense is dispatched to kill the infected lung cells and engulf its debris. If there is no engulfed debris, it needs to be expelled by cough. At the same time, neutrophils present in the blood also release proteases to kill the virus and engulf the infected cells. As these immune cells engulf infected cells, pus forms, which is inflammation. When the pus penetrates into the alveolar cavity and blocks the respiratory membrane, the patient will have difficulty breathing.

The first two lines of defense are the natural defense functions gradually established by humans during the evolution process. They are characterized by human beings. They are not directed against a specific pathogen and have a defense effect against multiple pathogens. Therefore, they are called non-specific immunity ( (Also known as innate immunity). In the process of defense against pathogens, non-specific immune cells can also attack the healthy cells of the body indiscriminately.

The new coronavirus is a completely new type of pathogen that cannot be cleared by the first two lines of defense of our body. It enters the alveoli and stimulates the second line of defense while stimulating our body to turn on the third line of defense. The third line of defense is mainly composed of immune organs (tonsil, lymph nodes, thymus, bone marrow, and spleen, etc.) and immune cells (lymphocytes, monocytes / macrophages, granulocytes, mast cells) through blood circulation and lymphatic circulation. . The third line of defense is the acquired defense function that the human body gradually establishes after birth. It is characterized by being produced after birth and only acts against a specific pathogen or foreign body, so it is called specific immunity (also known as acquired immunity).

After the pathogen invades, the lymphocytes are stimulated, and the lymphocytes will produce a special protein called the antibody against the pathogen. Substances that cause the body to produce antibodies (such as foreign bodies such as pathogens) are called antigens. The new coronavirus is a new antigen that our body has never encountered. Before stimulating the body to produce antibodies to clear the virus, it will constantly cross the first two or even the third line of defense, causing human disease. When our body's third line of defense is activated and can produce enough antibodies against the new antigen, the body will gradually clear the virus and heal itself.