The immune system in action

Our immune system protects us from pathogens. This interactive is a simple version of an immune system response when a virus (rotavirus) or bacteria commonly found on the skin get into the body.

To use this interactive, move your mouse or finger over any of the labelled boxes and select to obtain more information.

Transcript

Introduction

Our bodies have different systems that help us function. The respiratory system helps us breathe. The muscular system enables us to move. The skeletal system supports us, and the immune system defends our body against all foreign substances.

ACKNOWLEDGEMENT: University of Waikato

Immune system

Immune cells are produced in the bone marrow. They move rapidly through the body in the blood to get to the sites of infection, where they pass into tissues and then move between individual cells. They return to the blood by travelling via the lymphatic system. Lymph nodes are special sites where they collaborate to fight infection.

ACKNOWLEDGEMENT: University of Waikato

Virus immune response

There are hundreds of different viruses, and some can cause disease in humans.

This is rotavirus, which can spread rapidly on contaminated hands or objects. It damages cells of the small intestine, causing vomiting and diarrhoea. A rotavirus enters the body through the mouth. It travels to the small intestine or gut.

Viruses are tiny. We have magnified this virus so we can track it. The virus attaches to and invades the cells lining the gut.

The damaged cells send out signals to the dendritic cells, which are on the look-out for pathogens.

A dendritic cell can extend between two enterocyte cells. The dendritic cell uses its arm-like part to ‘fish’ for pathogens. The dendritic cell engulfs the virus and breaks it up.

Antigens appear on the surface of the dendritic cell. Meanwhile, some virus particles have begun replicating inside an enterocyte cell.

The dendritic cell migrates to the nearest lymph node and displays the rotavirus antigen on its surface.

If T cells entering the lymph node recognise the antigen they become activated and replicate. Activated T helper cells then interact with B cells.

If a B cell recognises the same antigen, it replicates and matures into antibody-producing plasma cells. Some of the replicated B cells mature into memory cells in case the rotavirus appears again. Then, the response will be stronger and faster.

The activated cells move out of the lymph node to the site where the dendritic cell found the rotavirus.

At the site, the B plasma cells release antibodies. The antibodies are picked up and transported through the enterocyte cell. They move into the intestine where they lock on to the antigen on the virus surfaces. This stops the virus from getting into the enterocyte cell, and it is washed away down the gut.

Meanwhile, the rotavirus that invaded the enterocyte cell has replicated.

A killer T cell shoots an enzyme into the enterocyte cell. The enterocyte cell is destroyed, but so is all the rotavirus that was inside the cell.

A macrophage cell is attracted to the dead cell. It engulfs and ingests the cell and the destroyed rotavirus.

ACKNOWLEDGEMENT: University of Waikato

Bacteria immune response

Our bodies are covered in bacteria. Some of the bacteria may be harmful. If our skin is broken, bacteria may get inside us. Immune cells called neutrophils ingest and destroy the bacteria. Many neutrophils are killed in the process, forming pus.

Macrophages are attracted by the dead cells and come to engulf and ingest them. However, some bacteria avoid the neutrophils and enter the body.

A dendritic cell, scouting for pathogens, finds the bacteria and engulfs some. Antigens appear on the surface of the dendritic cell.

The dendritic cell migrates to the nearest lymph nodes and displays the bacterial antigen on its surface. If T cells entering the lymph node recognise the antigen, they become activated and replicate.

Activated T helper cells interact with B cells. If a B cell recognises the same antigen, it replicates and matures into antibody-producing plasma cells.

Some of the replicated B cells mature into memory cells in case this bacteria appears again. Then the response will be stronger and faster.

The activated cells move out of the lymph node to the site where the dendritic cell found the bacteria.

The plasma B cells release antibodies. The antibodies lock on to the bacteria surface, which disables it from functioning and flags it for destruction.

The macrophage is attracted to the marked or flagged bacteria. The macrophage engulfs and ingests the bacteria.

Suppressor T cells come in to calm the immune cells and stop the fighting.

ACKNOWLEDGEMENT: University of Waikato