How you will define the immune system?
The immune system is defined as the body's defense system. This system protects and saves the body from the inside and outside pathogens.
Inside pathogen means any dead or faulty cells. They are recognized by the immune system and killed by the immune cells. Outside pathogens mean any harmful virus, bacteria, etc that come into the body. As they enter in the body, our immune system gets spark from the germs and them make antibodies against those antigens (foreign pathogen)
Antibodies:

Protective, Y-shaped, large protein, that is produced by the immune system in response to antigen.

Antigen

Any foreign pathogen that is injurious for our health which stimulates the immune system
Without the immune system, our body is vulnerable to the attack of pathogens. These pathogens include Viruses, bacteria, parasites, and other microorganisms that may harm the body.

Our immune system keeps us healthy and protects us from germs. Otherwise, we are living in the world of harmful pathogens. The immune system is involved many cells, organs, and proteins that work together in the form of a group.

The character involved in the immune system
Our white blood cells (leukocytes) are the main part of the body’s defense system.

White blood cells further include

Phagocytes

These cells engulf the pathogens and kill them. Phagocytes include the following cells

Monocytes

The largest type of phagocytes that have a different role in the body

Macrophage

They remove the dead and dying cells from the whole body
Neutrophils

The most common type of phagocytes that tend to attack the bacteria

Mast cells

Involve in the healing process of the wounds and protect the wound from the pathogens

Lymphocytes

Lymphocytes have a major role in the defense system. After the death of foreign invading pathogens, there is a chance of their again attack. Here these lymphocytes help the defense system by recognizing and remembering these previous pathogens.

Lymphocytes produce in the bone marrow. Some cells remain in the bone marrow while some move toward the thymus. Lymphocytes are further divided into two categories and get name according to their location

B-lymphocytes

After their birth, cells remain in the bone marrow and they become mature into B-cells.

T-lymphocytes

Cells that move toward the thymus and remain there permanently and become mature into T-cells.
B-cells invade the body and find the target then send the stimulus to the T-cells. T-cells become alert after getting the stimulus from the B-cells. T-cells make the antibodies against the pathogens then antibodies kill those antigens.

Working of the immune system

Working of the immune system is just like the working of intelligence and army of any country. As they save their country from the enemy, the immune system does it in the same fashion.

When any foreign antigen enters the body, the immune system recognizes it at once and tries to get rid of it. B-cells and T-cells play a major role in the immune system. B-cells find the antigens and send defenses to overcome the antigens. T-cells destroy those antigens.

They also send the signals to other body cells (phagocytes) to engulf and remove these dead antigens.
In the whole process, antibodies make, after their production and killing the antigens, they remain in the body so that body can’t be attacked again by the same germs. In short words, immunity is developed against that disease or germs.

The human immunity system is of three types, passive, innate and adaptive.

We will explain all three briefly.

Adaptive immunity

Adaptive immunity means activation of the immune system against any disease. When we suffer from any disease, our immune system becomes active against disease and makes antibodies against that disease. We also develop adaptive immunity, when we take a vaccine against that disease.

Innate immunity

Innate immunity means natural immunity. Every human body has a natural immunity in the form of skin. Skin save us from harmful germs and act as a barrier between the body and germs.

Passive immunity

Passive immunity means “gain or borrows” the immunity from others for a temporary time. For example, when a kid takes his mother's feed, he gets antibodies of those diseases to which the mother had been exposed once. It gives temporary immunity to the children.

When a child is born, his immune system may take some time to develop, and the vaccine assists it in this matter. So, the immune system gets strong over time. That is why doctors recommend the vaccine and emphasize it to vaccinate the child in time. So, don’t show any negligence in this matter because it is very important for your child’s immune system.

Author's Bio: 

Rizwan Amjad is marketing expert specializing in industries. He's also an SEO Practitioner by hobby and managing multiple blogs and works with various clients.