How Does The Immune System Work

Your immune system is a network of cells, tissues, and organs protecting your body from harmful substances. A healthy immune system can identify and fight off invaders such as viruses and bacteria before they can cause damage.

An informative blog post on how the human immune system works.

The Immune System: How does it work?

The blood carries white blood cells called lymphocytes which are part of your body's natural defences against germs.

Incoming bacteria and germs should be caught by these cells, but if new germs enter the body, they are not recognized as harmful.

If you get ill, your immune system has to fight off the infection. This is called an immune response.

Your immune system uses mainly two types of cells to protect against germs. These are:

Antibodies- These recognize germs and neutralize them. They also recruit other parts of the immune system to fight off an infection.

Antigen-presenting cells (APCs) - These take up a bacteria, virus or other foreign substance, degrade it and display small parts of it to other cells so they can react against them.

Many white blood cells, which make up the immune system, are part of a single network.

The lymph nodes are connected by lymph- vessels, which carry fluid containing white blood cells around the body.

B1 is a cell that shows up in bowel disease and colitis (inflammatory bowel disease), also called Crohn's disease. B1 is a cell that shows up in bowel disease and colitis (inflammatory bowel disease), also called Crohn's disease.

The immune system is composed of many different types of cells.

A B cell produces antibodies which are proteins that recognize and attack germs.

B lymphocytes (B cells) make antibodies. An antibody can be a molecule or an organelle. Antibodies have many functions in the immune system, including binding to viruses and bacteria, triggering other cells to destroy them, and helping B cells to recognize new invaders.

B lymphocytes are present in most parts of the body, but their primary purpose is to make antibodies that will help fight infections.

Antibodies have a short lifespan, so new ones are produced continuously at the same time as your body's immune system clears out old ones.

Antibodies react with other molecules on the surface of invading germs.

An antigen is a molecule or a set of molecules that can cause your immune system to make antibodies against it. Antigens include foreign substances, such as bacteria and viruses, and components of your own body, such as tissues/cells from another part of your body or your baby after birth.

B cells have different roles depending upon the types of antibodies they can produce.

A particular type of cell called a memory B cell can make large amounts of the antibody that it would have made when first exposed to an antigen.

Memory B cells are a type of B cell that can remain in the body for many years and remember how to make antibodies to particular foreign substances (antigens) that they have seen before.

A memory B cell can react quickly when it reencounters its antigen, making large amounts of antibody in a short time.

Memory B cells remember an antigen even after many years. They have two essential functions:

Plasma cells are white blood cells that produce antibodies. Antibodies are large proteins that recognize and bind to foreign substances called antigens, which trigger an immune response (a process by which the body's natural defences destroy infectious agents such as bacteria and viruses). The plasma cells are involved in the immune response to infection.

Plasma cells are present in almost all tissues, but especially in the spleen.

Plasma cells make specific antibodies that destroy invading molecules called antigens.

Different B cell types exist which can produce various kinds of antibodies, which target foreign antigens.

They can recognize different foreign substances and react accordingly. Different B cell types exist which can produce various kinds of antibodies, which target other antigens. They can identify different foreign substances and respond accordingly.

Young cells in the bone marrow will make B cells. They are called PB1+. In this slide: PB1+ from the bone marrow has been combined with a B cell, split to produce plasma cells and memory B cells.

When B cells are present in the blood, they often cluster together in large numbers. This is due to the chemical signals released by other white blood cells which attract them. These clusters of B cells can be seen floating in sections of blood under a microscope or on a slide under a microscope.

When B cells cluster in this way, they are called B cell follicles.

B cells recognize foreign substances (antigens) through a molecule that is attached to their membrane. This antigen-binding molecule is called a B cell receptor (BCR).

The BCR has two main parts: a part that recognizes the antigen and a signalling part. The signalling part allows the B cell to alert other parts of the immune system to produce antibodies against the invading substance.

The proteins that are attached to the membrane of T cells, another type of white blood cell, recognize antigens and activate them.

B and T cells work together to identify antigens that can trigger an immune response.

The B cell receptor (BCR) is composed of two parts that can recognize a specific antigen.

B cells secrete antibodies into the blood and lymphatic system. They travel through the bloodstream until they bind to an antigen. A B cell goes through several changes as it develops:

A B cell starts life as a stem cell in the bone marrow (BM).

B cells need a signal from a T helper cell before they start to produce antibodies. These are made in response to 'antigens', which are foreign substances that trigger an immune response by activating B cells.

Memory cells and plasma cells can destroy antigens when they have bound to them through antibodies.

Molecules in the plasma cells and memory cells can attach to antigens. This helps kill the invading germs.

Plasma cells can make large amounts of antibodies that react with a specific antigen.

The immune system can recognize foreign molecules in the body. Without the immune system, we would not survive because many infections are caused by bacteria that enter the body or germs that enter through wounds on our skin.

Antibodies, which are made by B and T cells, work together to destroy bacteria and viruses inside our bodies. The antibodies bind to the antigens of infectious agents or substances and inactivate them or mark them for destruction by phagocytic cells such as macrophages.

The immune system is a complex network of cells, tissues and organs that together protect the body from infection. It forms barriers that keep germs out and has a sophisticated surveillance system that attempts to detect them if they do enter the body.

It can destroy some organisms on contact and other microorganisms it keeps under control or destroys after multiplying. This is known as acquired immunity (by acquisition).

There are two main types of T cells: helper T cells and cytotoxic T cells.

T helper cells help B cells to make antibodies, promote phagocytosis (the process by which foreign matter is engulfed by white blood cells) and help with the maturation of new B cells.

Cytotoxic T cells can recognize certain kinds of protein on the surface of cells. They can also identify and bind to specific types of bugs, such as bacteria and viruses that have entered the body. When it binds, the cytotoxic T cell releases chemicals that kill the target cell.