After reading this popular science, it is equivalent to reviewing immunology knowledge

Immune cells are like the "police department" in the human body.
They are responsible for removing trash such as apoptotic cells, traitors such as tumor cells, and foreign enemies such as viruses and germs.

As a "departmental employee", healthy and vigorous immune cells are our extremely precious treasure of life.

The immune system is the guardian of the body.
It is composed of immune cells, immune organs, and immune substances.
It fights against foreign pathogens and mutated cells in the body to maintain the health of the human body environment.

For example, tissues such as skin and mucous membranes, as the innate immune system, are the first line of defense to prevent foreign bodies from entering the body.

And every person has trillions of cells replicating every day.
Under the influence of carcinogens (smoking, ionizing radiation, Helicobacter pylori, etc.
), about 500,000 to 1 million cells can mutate during the replication process.
Some The mutant cells further become cancer cells.

The reason why we don’t get cancer is our immune system.
The best "doctor" in the world has been dealing with cancer cells.
On the one hand, the immune system recognizes and eliminates invading bacteria, viruses, etc.
, on the other hand, it also Eliminate mutated tumor cells, senescent cells, dead cells or other harmful components in the body.

Come and get to know the powerful immune system in our body.

1.
The composition of the immune system I (the immune system) is the "army" of the human body (this country), protecting the body at all times and resisting the intrusion of internal mutant garbage and foreign pathogenic microorganisms.

People often call this protective function of mine immunity.

Let me first talk about the composition of my "army".

The immune system is divided into two categories: innate immunity and acquired (acquired) immunity.

Innate immunity is born from birth.

Acquired immunity is gradually acquired in the course of survival after birth.

Recently, people are used to divide them according to our functions, as follows: (1) Innate immunity Innate immune cells include mast cells, macrophages, NK cells, neutrophils, and DC cells.

The distribution and sub-tools of immune cells in the body have important strategic significance.

Mast cells are the "sentinel" cells that guard the body's portal.
They are mainly distributed in the skin, submucosal tissues and around the blood vessel walls through which microorganisms must enter the body.

They recognize various danger signals unique to microorganisms, and then release the inflammatory factors in the cytoplasmic granules, call various immune cells to the invaded tissue site, and initiate the inflammatory process.

Macrophages are "resident frontier guards" distributed in various tissues throughout the body.
They have strong phagocytic and killing capabilities and are the first main line of defense for microorganisms after they pass through the body's surface.

Neutrophils, which account for 2/3 (60-70%) of the total number of white blood cells in the peripheral blood, are "field forces" that constantly patrol the body with the blood circulation, and can penetrate blood vessels under the chemotaxis of chemotactic agents (biochemical substances).
The wall quickly reaches the infected tissue site and performs the function of phagocytosis and digestion of microorganisms or other microorganisms.

Neutrophils have a lifespan of only a few days, so they are also called the "death squad" of the immune system.

Macrophages and neutrophils are collectively called phagocytes.

Natural killer cells (NK cells) are important immune cells in the body, not only related to anti-tumor, anti-viral infection and immune regulation, but also involved in the occurrence of hypersensitivity and autoimmune diseases in some cases.

Natural killer cells are lymphocytes that do not have typical T and B lymphocyte surface markers and characteristics.

It is derived from bone marrow lymphoid stem cells and matures in the bone marrow.

It mainly exists in blood and lymphatic tissues.
There are azurophilic granules in the cytoplasm of the cells, so they are called large granular lymphocytes.

The guardian of killing cancer cells-NK cells (2) Adaptive immunity As animals evolve from lower to higher levels, the immune system in animals has also changed from simple to more complex and effective.
When vertebrates have appeared, they have become more complex and effective.
Memory and memory function of the adaptive immune system. "Adaptability" here means that the immune system changes its own state after being stimulated by microorganisms or other foreign substances in the living environment, and acquires immunity against the microorganisms or antigens, and can be more Effectively complete the mission of defense.

In fact, the adaptive immune system is a leap based on the innate immune system, which adds "modernized" components and functions to the immune system.

One of its main features is its ability to distinguish subtle differences between different microorganisms or antigens, which seems to be a bit similar to the "precision strike" of modern warfare.

Therefore it is also called the specific immune system.

T lymphocytes and B lymphocytes are the "modernized" army of the immune system.

The total number of lymphocytes in the human body is equivalent to the number of brain cells or liver cells.

They use the lymph nodes as a "camp", constantly circulating between the blood and the lymphatic system.

T cells and B cells recognize antigens through the T cell receptor (TCR) and B cell receptor (BCR) that they express, and adapt immune responses (reactions).

It can be divided into cellular immune response and humoral immune response.

Coordinated combat forces: helper T cells and B cells are activated after BCR recognizes the antigen, begin to proliferate and further differentiate into plasma cells.

The main function of plasma cells is to synthesize and secrete antibodies, also known as immunoglobulins.

The antibody molecules secreted by B cells have the same antigen specificity as BCR.

The top (Fab segment) of the "Y" antibody molecule is its antigen recognition site.

After the antibody molecule is combined with the microorganism, it can play three roles: prevent the microorganism from continuing to infect other cells; activate the complement to directly kill the microorganism; through the Fc segment of the antibody molecule binds to the phagocytes, the complex is captured and cleared.

T lymphocytes are divided into two categories: CD4 and CD8.

The former are helper T cells, which are the "commanders" of the immune response.
They exchange information with other cells and give orders through the molecules on the membrane surface and the secreted cytokines. CD8 T cells are killer T cells, which can directly kill host cells infected by microorganisms and eliminate the "processing factories" and "safe harbors" of pathogens in the body.

Complement is one of the important members of the Great Wall of the human body.
It is not a single component, but a complex system composed of many proteins.

It is also called the complement system, because it is called Complement in English; therefore, the first letter C is used to represent complement.

The inherent components of complement are called C1, C2, C3.
.
.
C9 according to the Arabic alphabetical numbers, and there are two other components called factor B and factor D; usually when we see a doctor in the hospital, the doctor’s laboratory test sheet says C3 , It means to check the third component of complement in the blood.

Under normal circumstances, the various components of complement are relatively stable, but once they are triggered (such as the combination of microorganisms and antibodies).

They acted like chains one by one in order to defend our body.

In addition to the inherent components of complement, there are also some regulatory components like our monitoring agencies.
They can control the intensity of complement actions, so that they will not act excessively without distinguishing between enemy and ourselves, or even destroy their normal tissues and cause diseases.

What exactly does complement "make up"? From a traditional perspective, it was initially discovered that the role of complement was mainly to assist antibodies to kill harmful foreign microorganisms, so it was called complement a long time ago.

In fact, the development of modern science and technology has shown that complement is far more than supplementing antibodies, but actively participating in various activities of the immune system.
It is an important and complex system that is indispensable to the Great Wall of the human body.

2.
Immune principle of the human body.
I have many occupations in the human body.

Just like a country, there are "National Defense Forces", "Public Security Bureaus", and "Cleaning Teams.
"
Sometimes I serve as a soldier, sometimes on duty, and sometimes as a cleaner.

Today I will tell you how I completed these professions.

According to the different pathogens to be guarded against, it is divided into two types: specific immunity and non-specific immunity.

Specific immunity can only prevent one kind of bacteria or one virus infection.

For example, taking polio sugar pills can only prevent polio; taking hepatitis B vaccine can only prevent hepatitis B.

Non-specific immunity means that all bacteria and viruses can be prevented.
For example, all bacteria on the skin can be blocked, and interferon can "interfere" with all viruses.

Specific immunity is acquired after birth.
It is a certain specific immunity acquired through vaccinations, vaccinations or exposure to pathogenic microorganisms after suffering from a certain disease; non-specific immunity is innate and is given by parents.
Yes, it was born.

The mammalian immune system is the product of the superposition of the innate immune system and the adaptive immune system.

The former is the basic line of defense, while the latter is specific and has memory characteristics.

The two systems cooperate with each other and complement each other to provide the body with effective anti-infection and immune protection.

The body's radar: dendritic cells (DC cells) 3.
Specific immunity: targeted prevention, and some people understand that specific immunity starts from smallpox.

It was more than 1,000 years ago, when smallpox was raging.

As people came into contact with smallpox, they gradually discovered that not only smallpox patients who survived a catastrophe will no longer get smallpox, but some people who have been in contact with smallpox patients will not get smallpox either.

This inspired people.
People began to peel off the scabs of smallpox patients, grind them into powder after drying, and blow them into the noses of people who have never had smallpox, hoping to prevent smallpox.

The result was a success.

People who have been blown smallpox scabs really don't have smallpox.

After hundreds of years of exploration, the "vaccinia" vaccine that we later vaccinated was finally born, and smallpox was eventually eliminated.

Since then, human beings have also begun to develop various vaccines, and now they have been able to produce many vaccines to prevent a variety of infectious diseases.

For example, children's vaccines can prevent diphtheria, whooping cough, and tetanus.
The hepatitis B vaccine that children and adults can inject can prevent hepatitis B and so on.

So, how does this specific immunity come about? This has to start from the "root"-bone marrow.

Bone marrow is an immune organ.

There is a very important cell in the bone marrow called bone marrow hematopoietic stem cells, which has a variety of differentiation potentials.
Just like an 18-year-old recruit enlisted in the army, it can be trained as a communicator or an artillery.

Stem cells can become red blood cells, white blood cells, phagocytes, etc.
according to the needs of the body, some of which become lymphoid stem cells.

Lymphatic stem cells are divided into two ways: one way stays in place, turns into B cells in the bone marrow, and then reaches the spleen and settles in the lymph nodes with the blood; the other way reaches the thymus with the blood, differentiates into T cells in the thymus, and also arrives with the blood.
The spleen, lymph nodes, and B cells are on standby together to prepare for immune function.

After external pathogenic microorganisms (doctors call them antigens) invade the body, if they can "pass five barriers and kill six generals" into the blood to reach the spleen and lymph nodes, T and B cells should play a role.

First of all, T cells will enter an activated state when stimulated by this pathogenic microorganism, and become what doctors call sensitized T cells.

Sensitized T cells have two characteristics: one is that it has the ability to attack this pathogenic microorganism and can kill it; the other is that it has recognition and memory functions for this pathogenic microorganism, and the next time you see this pathogenic microorganism Be able to recognize it and continue to attack it.

B cells will produce a substance under the stimulation of pathogenic microorganisms.
This substance can bind to the pathogenic microorganisms and make them inactive.
Doctors call this substance an antibody.

If this pathogenic microorganism invades the body again in the future, sensitized T cells (which activate T cells) will rush forward to fight against them, and antibodies will bind to them and make them lose their ability to cause disease.

It can be seen that as long as the body's immune system has seen a certain pathogenic microorganism once, it has immunity to that pathogenic microorganism.

This is why people can be immune to this pathogen as long as they have taken or injected a certain vaccine, or have had this infectious disease.

Natural enemies of tumors: Cytotoxic T cells (CTL) 4.
Non-specific immunity: Comprehensive prevention of non-specific immunity is composed of three lines of defense.

The first line of defense: mechanical barriers, such as the skin and mucous membranes mentioned above, are responsible for preventing pathogenic microorganisms from entering the body.

The second line of defense: phagocytic cells, which exist in the blood and various tissues, are used to swallow and destroy pathogenic microorganisms such as bacteria and viruses that enter the body.

The third line of defense: There are many antimicrobial substances in blood, tissue fluid and various secretions.
For example, lysozyme in saliva can dissolve bacteria that enter the oral cavity.
After human cells are infected by viruses, they can produce interferon and interferon.
Can kill the virus.

It can be seen that non-specific immunity is the basis of specific immunity, and specific immunity and non-specific immunity complement each other and jointly maintain human health.

Take bacteria as an example.
If a certain type of bacteria enters the human body from the respiratory tract or digestive tract, the mucosa of the respiratory tract or digestive tract first blocks it; if it is not blocked, it enters the blood or tissues, and the phagocytes fight against it—eat it.
Or destroy it; if it has not been eliminated, it will enter the lymph nodes and spleen, where T cells will become sensitized T cells under its stimulation, and B cells will produce antibodies under its stimulation and continue to interact with it.
struggle.

In the future, if this kind of bacteria invades again, more sensitized T cells with recognition function will be produced, and B cells will also produce more antibodies, making the body more powerful to fight against this kind of bacteria.

This is how the immune system works for you.

How, is it your inseparable protector.

5.
Rejection and allergic reactions.
Rejection: blindly rejecting "differents".
As you already know, as the immune system, I have the ability to recognize foreign pathogenic microorganisms.

In fact, I can identify not only pathogenic microorganisms, but also all foreign objects, as long as it is not the tissue cells of my master, I know them and attack them all.

Because the appearance of the cell surface of each person is different from that of each person, doctors call this difference "antigen difference" and call this ability "self-recognition ability.
"
It is precisely because of this "self-recognition ability" that it can take on the three major functions of immunity.

However, sometimes mistakes are made because of this ability.

My code of conduct is: everything that is good to me is resolutely protected; everything that is foreign is bad and rejected.

The problem will follow.

To give an example that everyone is most familiar with, for example, my master was injured, very seriously injured, and needed a blood transfusion.

But no matter how critical, the blood type of the blood transfused must be the same as my host’s blood type (that is, the same antigen), otherwise, I will reject the blood transfused into the host’s body as an alien.
The doctor calls it a "hemolytic reaction.
" , That is, the red blood cells that enter the host's body are lysed.

Another example is transplant rejection.

If one of the host’s organs—the kidney (heart, etc.
, any organ) fails, and there happens to be a kind person willing to donate his kidney to the host.

It should be said that this is a good thing, but not because I can't pass my level.

I can't let any "alien" matter into the host's body, because I can't distinguish between good and bad.

This is troublesome.
Although mankind has completely solved the technical problem of organ transplantation, and in many cases, it can also solve the problem of organ donors, but it is because I cannot pass my test that humans are still unable to perform organ transplantation as they like.

I don't know how many people who need organ transplantation are desperate because of me.

This is the first mistake I made when I was "loyal to my duty.
"
Allergic reactions: Autoimmune diseases.
It stands to reason that I should be able to recognize "my" substances and not produce an immune response to my own tissue cells.
Sometimes errors may occur.

Sometimes it's my problem, sometimes it's the owner's problem.

For example, sometimes people are infected with streptococcus, get tonsillitis, and suddenly get nephritis after half a month.
This is the problem with my recognition function.

It turns out that streptococcus and human kidney cells look similar in part.
I originally wanted to produce antibodies against streptococci.
Because of the recognition error, I produced antibodies against my own host’s kidney cells, which resulted in nephritis.

Sometimes it's the owner's problem.
For example, he took some drugs or received ionizing radiation, which caused his own tissue cells to change and look different from the original.

Of course I couldn't recognize it clearly, and thought it was a "foreign object".

As a result, antibodies are produced and attacked, resulting in many diseases.

Sometimes, simply "for no reason" (in fact, it may be that I haven't figured it out yet), I will "for no reason" produce antibodies against my own host cells, causing autoimmune reactions.
Doctors call this type of disease.
It is an "autoimmune disease".

Autoimmune disease is a very troublesome disease.
Think about it, no one has recruited you.
If you can't get through with yourself, what's the trick? Therefore, many doctors get headaches when they mention this disease.

Cancer cell (Cancer cell) does not distinguish between friends and foes: "The flood washed the Dragon King Temple.
" Sometimes, it was neither a foreign antigen, nor did I make any mistakes, but something went wrong.

For example, after some people have suffered serious eye injuries, doctors will mobilize patients to remove their eyeballs in order to prevent "sympathetic ophthalmia.
"
What is sympathetic ophthalmia? It turns out that the tissue inside the eyeball has been wrapped since birth and has never entered the blood, lymph nodes and spleen.
T cells and B cells have never been in contact with them, so naturally they do not recognize them.

When the eye (such as the left eye) encounters a trauma, the left eyeball ruptures, the tissue cells in the left eye will inevitably enter the blood, and I am stupefied-"What is this?" "I haven't seen it, it must be a foreign body .

"so I started to produce antibodies to the eye tissue.

Antibodies do not distinguish between left and right.
Naturally, the left and right eyes fight together, so "a cold in the left eye followed by a cold in the right eye" occurs, which is what doctors call sympathetic ophthalmia.

The final result is that the right eye cannot be saved, so the doctor has to ask you to remove the injured left eye in order to achieve the goal of "losing the pawn and protecting the car.
"
There are several other conditions like eyeballs.
For example, the thyroid gland and the testicles of men are always in the package, so even though they are my own family members, I don’t know them.

It was like treating a relative in the family.
He was originally a family, but because he has been out of town, I have never seen him.
One day he suddenly visited him.
I didn’t know him, so I naturally regarded him as an outsider and held a repulsive attitude.
The attitude is naturally bad.

Article Source: Stem Cell Say