What is Immune System? | Types, Definition, Structure, Function & Facts

What is the Immune System?

The immune system helps protect us against illness caused by tiny invaders (called pathogens) like viruses, bacteria, and parasites. The immune system is made up of specialized organs, cells, and tissues, all of which work together to destroy these invaders. Some of the major organs involved in the immune system include the spleen, lymph nodes, thymus, and bone marrow.

How does it work?

The immune system develops all kinds of cells that help destroy disease-causing bacteria. Some of these cells are specifically designed for a certain disease. Throughout the body, disease-fighting cells are stored in the immune system waiting for a signal to go to war.

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The immune system can communicate throughout the body. When pathogens are detected, notifications are sent warning that the body is under attack. The immune system then directs the good attack cells to the problem area to destroy the invaders.

Antigens and Antibodies

Scientists call invaders can cause disease-causing antigens. Antigens trigger an immune response in the body. One of the main immune responses is the production of proteins that help fight antigens. These proteins are called antibodies.

How do the Antibodies know which cells to attack?

To function properly, the immune system needs to know which cells are good and which ones are bad. Antibodies designed with specific binding sites bind only to certain antigens. They ignore the “good” cells and only attack the bad ones..

Types of Immunity Cells

The immune system has cells that perform specific functions. These cells are found in the blood and are called white blood cells.

B Cells – B cells are also known as B lymphocytes. These cells produce antibodies that bind to antigens and neutralize them. Each B cell produces a specific type of antibody. For example, there is a specific type of B cell that helps fight the flu.

T cells – T cells are also known as T lymphocytes. These cells help get rid of good cells that have become infected.

Helper T Cells – Helper T cells command B cells to start making antibodies or tell killer T cells to attack. Killer T Cells – Killer T cells destroy cells that have been infected by invaders.

Memory Cells – Memory cells remember antigens that have previously attacked the body. They help the body fight any new attacks by a particular antigen

How do we get Immunity?

The immune system is very intelligent and can adapt to new infections. Our body acquires immunity in two ways: active immunity and passive immunity.

Active immunity – When our body develops immunity over time through the immune system, it is known as active immunity. Every time we are exposed to disease (and sometimes get sick), the immune system learns to fight the disease. The next time a disease invades, our bodies are ready and able to quickly produce antibodies to prevent infection. We can also achieve active immunity through vaccines.

Passive immunity – When we are born, our bodies may already have some immunity. Babies receive antibodies from their mothers as they grow in the womb. They can also get antibodies from breast milk. It is also possible to obtain antibodies from other animals or humans through immunoglobulin treatments. These are all passive immunity as they are not developed by our body’s immune system.

How Vaccines Work

Vaccines introduce germs that have been killed or mutated so that we don’t get sick. However, the immune system does not know this. It builds defenses and antibodies against disease. When the disease actually tries to attack, our bodies are ready and able to quickly neutralize the antigens.

Interesting Facts about the Immune System

Part of the immunity eventually wears off, so we need a new vaccine after a while.

Different people have different levels of immunity to certain diseases. This is why some people get sick more often than others.

Sometimes the immune system can mistake and attack the right cells. Type I diabetes occurs when T cells attack the insulin-producing cells in the pancreas.

Both T cells and B cells are stored in lymph nodes throughout the body. They enter the bloodstream when needed to fight disease.

Your body reacts much faster and stronger when it sees an antigen a second time.