An interactive showing immune response.

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Rights: University of Waikato. All rights reserved. Published 24 June 2016 Referencing Hub media

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

The animation is split into four sections. Click on any of the four buttons at the start to play the animation. The controls are located at the bottom right hand corner.

You will need the Adobe Flash Player to view it.

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.

Immune System

Immune cells are produced in the bone marrow. They move rapidly through the body in the blood to get to 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.

Inside Lymph Vessel

Dendritic Cell

Dendritic cells are a bit like spies sitting in among other cells. If they detect pathogens (foreign substances) within the body, they will ingest some, and molecules of the pathogens, called antigens, appear on the surface of the dendritic cell. The dendritic cell then leaves the site of infection and moves to the nearest lymph node. It stays there for about a week, displaying the antigens to the T and B cells that move through the lymph node.

Acknowledgement: Prof Gareth Jones, Wellcome Images

Macrophage

Macrophage means ‘big eater’. These cells ingest and clean up messes that include disabled cells or viruses that have been flagged with antibodies and dead cells.

Acknowledgement: MRC NIMR, Wellcome Images

Inside Lymph Node

T helper cell

T helper cells are coordinator cells. They give instructions to other cells by secreting certain proteins, called cytokines. T helper cells are responsible for activating other immune cells. Each T helper cell can only recognise one antigen.

Acknowledgement: David Darling

Suppressor T cell

When the infection is gone, the immune system needs to be calmed down or killer T cells may keep on killing good cells. The suppressor T cells (or regulatory cells) slow down or turn off the immune system to prevent damage to good cells.

Acknowledgement: Public Domain

Killer T cell

Killer T cells (or cytotoxic T cells) destroy pathogen-infected cells by shooting an enzyme into them. This makes the cell break into small pieces that can be eaten by nearby macrophages.

Acknowledgement: Science Online, BSIP Lecaque/Science Photo Library

B cell

When stimulated by the presence of a particular antigen, B cells mature to become antibody factories known as plasma cells, which cells release antibodies specifically to target that antigen.

Acknowledgement: Mesoblast Limited

Inside Blood Vessel

Antigens

Antigens are molecules from pathogens or foreign substances such as bacteria or viruses. Antigens appear on the surface of cells that have ingested or been invaded by pathogens and cause the immune system to respond.

Acknowledgement: Centers for Disease Control and Prevention

Bacteria

Bacteria are single-celled microscopic organisms. While most bacteria are harmless, there are some are pathogenic and cause us harm.

Acknowledgement: Centers for Disease Control and Prevention, Dr Ray Butler

Virus

Viruses are very basic (and tiny) microorganisms that are not considered living. A virus is genetic material wrapped up in a protein coat. Viruses hijack cells and use the cells to replicate themselves. Viruses can be pathogenic and cause us harm.

Acknowledgement: Sebastian Kaulitzki

Antibodies

Antibodies are released by plasma cells that are produced by B cells. Antibodies attach to the specific antigen they were produced for, disabling and marking the pathogen for disposal.

Acknowledgement: The University of Waikato

Neutrophil

Neutrophils are often the first cells to leave the blood and fight incoming pathogens. They only live a few days. Dead neutrophils accumulate as pus.

Acknowledgement: Centers for Disease Control and Prevention

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 out between 2 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 then 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 cells 
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 cells 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.

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.