Immune System

Immune System

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The immune system is a group of proteins and cells that help your body fight infections. Pathogens, like viruses, bacteria, and toxins, cause these infections. You can catch them from others when they cough or sneeze, or by eating or drinking contaminated food or water. Keeping your immune system healthy is important for staying well. 

The function of the immune system

The main parts of the immune system are the white blood cells, antibodies, bone marrow, the complement and lymphatic systems, and two organs, the spleen, and thymus.

The role of bone marrow in the immune system

Bone marrow is a soft tissue found inside bones that helps produce red and white blood cells as well as platelets. Platelets are small cell fragments that help stop bleeding by forming clots. Red blood cells not only transport oxygen, but also play a new role in the immune system. They can be stimulated by cytokines, which are proteins that help trigger inflammation. So, keeping your bone marrow healthy is important for producing healthy blood cells and platelets that help your body fight against infections and bleeding.

The lymphatic system aids the immune system

The lymphatic system plays an important role in both the immune and circulatory systems of the body. It's made up of organs, vessels, and tissues that move a clear fluid called lymph throughout the body. Lymph is made up of a variety of things, including damaged cells, viruses, and bacteria. This fluid helps transport white blood cells, called lymphocytes, to where they need to go to fight off invaders. The body also has around 600 small bean-shaped glands called lymph glands. These glands help produce and store immune cells, and filter out damaged and cancerous cells from the lymph fluid. So, the lymphatic system is a powerful tool for keeping your body healthy and fighting off infections.

The lymphatic system in the human body


The role of the spleen in the immune system

The spleen is an organ in the shape of a bean. It has red and white tissue, each colour having a different function. The red tissue stores blood and removes damaged blood cells, whilst the white tissue is part of the lymphatic system and helps produce white blood cells, producing antibodies.

The role of the thymus in the immune system

The thymus is a small pyramid-shaped organ located in the chest in front of the heart. This organ creates T cells by transforming white blood cells the bone marrow produces into them. As organisms age, the thymus begins to shrink and turn into fatty tissue, and the rate of T cell production declines. Organisms with a damaged or missing thymus are vulnerable to infections.

What is an overactive immune system?

Occasionally, the immune system can react heavily to things in the environment that are considered harmless such as dust, mould, pollen, pet dander, or foods. These things that cause the immune system to react are called allergens, and when the body responds to these allergens, it is called an allergic reaction.

For example, asthma is caused by the body reacting to allergens such as pollen, dust, or smoke.

Function of the immune system

There are two types of the immune system, the innate immune system and the adaptive immune system. Each of these immune systems works differently to help keep the body safe.

The innate immune system

The innate immune system is responsible for preventing infections from happening in the first place. It uses the body's openings and skin to keep disease out of the body. Various parts of the body contain lysozymes that work by breaking down the cell walls of different viruses. Additionally, the innate immune system sends consumed pathogens from food to the stomach, where the highly acidic environment destroys them. If a virus does make it into the body, the innate immune system responds by using inflammation, where white blood cells consume the pathogens, resulting in swelling of the affected area. Fever is another response that helps slow down pathogen reproduction. The complement system is a part of the innate immune system that helps activate plasma proteins found in the blood to fight off pathogens. It activates inflammation, labels pathogens and cells that need to be destroyed, and kills those pathogens and cells. Overall, the innate immune system is a vital defense mechanism that helps keep the body healthy and free of infections.

The adaptive immune system

The adaptive immune system, also known as the specific immune system, is responsible for targeting specific pathogens in the body. Cells that do not belong to the body are identified and attacked by other cells because our bodies can recognize which cells are our own. If a pathogen is encountered for the first time, the body is usually able to remember it and fight it off more effectively the next time. The adaptive immune system is triggered by antigens, which are cells that live on the surface of pathogens. When the body creates antibodies, a type of protein, they attach to the antigens and destroy them. This process helps the body fight off infection and develop immunity to certain diseases. Overall, the adaptive immune system is an essential defense mechanism that helps the body fight off pathogens and stay healthy.


Antibody and antigens bond
Antibody and antigens bond


Different types of immunity

There are two types of immunity, humoral and cell-mediated immunity, each playing its role in the immune system.

What is humoral immunity?

Humoral immunity, also known as antibody-mediated immunity, is activated when antigens are found in the body. Once these antigens are detected, B cell lymphocytes, a type of white blood cell, perform a differentiation that creates memory B cells and effector B cells. Memory B cells remember the current pathogen, making the production of antibodies faster in the future, and the effector B cells release antibodies.

What is cell-mediated immunity?

Cell-mediated immunity is a type of immune response that relies on the collaboration of T cells, macrophages, and cytokines to destroy antigens. T cells, which are a type of white blood cell, are created by the thymus and bone marrow stem cells and are capable of targeting specific antigens. There are two types of T cells: cytotoxic T cells and helper T cells. Cytotoxic T cells release toxins into infected cells, causing them to die, while helper T cells notify other cells in the body about the presence of antigens. Macrophages are specialized cells that help remove diseased and damaged cells from the body. They also help T cells by presenting them with antigens and releasing cytokines to activate the immune response. Cytokines are proteins that help cells communicate with one another and initiate the inflammatory response. Together, T cells, macrophages, and cytokines work to identify and destroy antigens, protecting the body from disease and infection.

How can an immune system be damaged?

The immune system can be damaged either by viruses or by lifestyle choices. Lifestyle choices, consisting of smoking, drinking, or poor nutrition, impact the immune system because they can harm the production and activity of immune cells. Viruses, like HIV, damage the immune system by attacking and destroying T cells, making it harder for people with those viruses to fight off other infections such as a common cold.

Immune System - Key takeaways

The immune system uses different proteins and cells to help keep the body safe. Pathogens are what infects the body and causes illness. These pathogens come from viruses, bacteria, and toxins. Lifestyle choices and viruses can damage the immune system. Most cells in the immune system are white blood cells. Two systems make up the immune system: adaptive and innate. The adaptive immune system targets pathogens explicitly. The innate immune system prevents all pathogens from using generic protection methods.

Immune System

What is the immune system? 

The immune system keeps the body safe from pathogens using different cells, organs, and proteins. 

What are the three major functions of the immune system? 

The three major functions of the immune system are destroying pathogens, destroying toxins, and taking care of cells that could harm the body, for instance, cancer cells. 

What are the five parts of the immune system? 

The five parts of the immune system are white blood cells, antibodies, bone marrow, the systems, and the organs. 

What can damage your immune system? 

Viruses can damage the immune system, but it can also be damaged by poor diet, smoking, and drinking. 

How does the immune system work? 

The immune system works by preventing infection in general, innate immune system, and targeting specific pathogens, adaptive immune system.

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