Vaccine work
One of the functions of the human immune system is to recognize and eliminate foreigners. Each person’s cell surface has its own unique set of recognition molecules, just like a set of passports. The immune system will not attack the cells holding a full set of internal passes. .
When bacteria and viruses invade the human body, the immune system will find that their passport is different from its own, and initiate an attack. But when there are enough invaders, the immune system can't stop them, and people get sick. In order to improve its ability to defend against foreign enemies, the immune system will record the passes of the pathogens that have been killed. Once the same enemy invades again, it can quickly mobilize the defense force. In this way, more invaders can be guaranteed to be prevented.
This is how the vaccine works. First, send a few dying enemies, or enemy passes into the body, so that the immune system can recognize them, and the enemies coming back in the future will be easily blocked.
Because the vaccine allows a group of substances with little harm to invade the human body and activates the body’s specific immunity to this substance, the body can quickly mobilize a defense force against this substance in the next few years or decades. It is normal for some people to have mild adverse reactions such as low-grade fever, local pain, redness and swelling after the vaccine. These reactions are caused by the active work of the immune system.
"Antigen" and "Antibody"
The characteristic molecules on the surface of various pathogens are called "antigens", and the defense fighters summoned by the immune system are "antibodies". Antibodies can specifically bind to antigens to initiate a series of immune responses. The antigen-antibody reaction is highly specific. Each antibody can only recognize one antigen, but different parts of an antigen molecule can be recognized by different antibodies.
Adaptive immune system
Antibodies constitute "immunoglobulins" and there are five types, namely IgM, IgG, IgE, IgA and IgD. Sometimes people will receive an "immunoglobulin" injection, which is essentially an injection of antibodies, which is equivalent to external reinforcements to help us fight off invading pathogens.
The lymphocytes in our body are mainly divided into T lymphocytes and B lymphocytes. Each type of lymphocytes is divided into many sub-categories. Among them, "memory B cells" and "memory T cells" are mainly responsible for recording the antigens that have been exposed , And "plasma cells" are responsible for producing a large number of antibodies against specific antigens after receiving the signal, and there are many other cells that also participate in this defense battle in different ways.
Immune process
When the human body comes into contact with a certain antigen for the first time, it needs to go through a series of antigen recognition and presentation processes before it can produce antibodies to deal with this strange enemy. Therefore, antibodies can only appear in the blood after a period of infection. This is the window period for antibody detection.
The first antibody that appeared was mainly IgM, which had weak antigen-binding ability, low content, short maintenance time, and rapid decline in concentration. This is called the "primary immune response".
After this, the antibody concentration in the body drops to a very low level, but the memory cells will record the antigen information.
If it is invaded by the same antigen again, the immune system can quickly be activated, memory cells divide and proliferate rapidly, produce a large number of plasma cells, secrete antibodies, and the incubation period is significantly shortened. This is called a "re-immune response."
The main antibody for the second immune response is IgG, which has strong ability to bind to antigen, high content, and long maintenance time. The reason why vaccinations can prevent diseases is precisely because our immune system relies on these antibodies to defeat pathogens.
