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Recall the Role of the Immune System

Worksheet Overview

QUESTION 1 of 10

Did you know that the human body comes across hundreds and thousands of potential pathogens every day?

 

Image of bacteria, virus and fungi


The human body has loads of clever defences to protect itself from these invaders! These are called non-specific defences because they target any pathogen and aren't specific to a particular type. Let's look at these in more detail below.  

 

Image of bacteria

 

 

The First Line of Defence:

 

 

Physical Defences

The first line of defence is the skin. The skin is very tough and it pretty much covers the whole body. A pathogen has to get past the skin in order to get inside the body where conditions are great for replication. An ideal place for this would be something like a cut in the skin, for example. This is a physical barrier.

Another physical barrier is found in the nose. The hairs found in your nose help to trap any dust particles that may be a source of pathogens.

 

Image of ciliated cells

 

 

Mucus is another physical barrier. Mucus is produced by special cells found in the trachea and bronchi (the tubes that branch into the lungs).  It’s thick and sticky and perfect for trapping pathogens. The trachea is lined with special cells called ciliated cells. These contain tiny hairs which move backwards and forwards. This moves mucus out of the airways into your mouth (ready to be spat out or swallowed), a bit like a broom sweeping up a mess!
 

Chemical Defences

If a pathogen is sneaky enough to get past all of these physical barriers, our body uses chemical barriers to prevent infection. So what are these chemical barriers?

 

Image of eye

 

 

Enzymes in our eyes and saliva are an example of a chemical barrier. These enzymes are great at protecting us because they destroy any pathogen that tries to sneak in through our eyes or mouth.

Another example is the hydrochloric acid found in our stomach. This acid is very strong and can destroy pathogens that make their way to the stomach in food and drink. This is known as a chemical barrier.


 

So what happens if a pathogen gets past our first line of defence? This is where the immune system steps in -  our second line of defence.


 

The Second Line of Defence:


The immune system is made up of different types of cells. One type of cell is the white blood cell.

 

Image of antigens and antibody

 

 

Pathogens get into the body through bypassing the body's first line of defence. Pathogen cells have markers on their surface called antigens. Each pathogen has different antigens. White blood cells recognise these foreign antigens and will engulf and destroy these pathogens.

Other white blood cells make proteins called antibodies that fit the antigens of a pathogen like a puzzle. The antibodies stick to the pathogen’s antigens, allowing them to be clumped together.  This makes it easier for the pathogen to be detected and destroyed.

Some pathogens will produce toxins that make you feel ill. White blood cells will produce specific antitoxins that will neutralise the toxin.

 


Immunity

If you get chickenpox when you’re young you can’t get it again. Your body has developed an immunity to the disease. 

After you have been infected with the chickenpox virus, some of the white blood cells that made antibodies against it stay in your blood. These are called memory cells.

If you’re infected again, the memory cells reproduce and make antibodies very quickly so your immune system responds much faster the second time.

You destroy the pathogen before it can make you ill.

 

 

In the following activity, you will investigate how the body protects itself from disease​. 

What are some of the physical barriers the body uses as defence against invading pathogens?
 

Image of bacteria, virus and fungi

Skin

Stomach acid

Mucus lining the airways

Enzymes in the eyes and saliva

What chemical barriers protect the body from invading pathogens?

Enzymes found in the mouth and eyes

Mucus in the trachea

Skin

Stomach acid

Pathogen cells have markers on their surface.

 

What are these markers called? 

 

Image of bacteria, virus and fungi

Pathogens have markers on their surface called antigens.

 

What is the name of the protein that white blood cells make to fit the antigens?

 

Image of HIV virus attacking cells

Antibody

Antigen

Antitoxin

Some white blood cells surround pathogens and engulf them. Once engulfed, the white blood cell destroys the pathogen.

 

What does the white blood cell contain that destroys the pathogen?

Energy

Enzymes

Glucose

Hydrochloric acid is found in the stomach.

 

Why might this be a useful barrier against infection? 

 

Image of food

The strong acid can destroy any pathogen found in food and drink

The acid can stop the pathogen from producing antibodies

The acid can break up the food

White blood cells make antibodies with shapes that fit the antigens. Other white blood cells can then find and destroy the microorganisms.

The diagram below shows the measles virus.

(These are not the real shapes or sizes of the pathogen or antigen!).

 

Which antibody -  A, B or C -  will match up with the measles' antigens?

 

 

Image of measles pathogen    Image of antigens

 

Fill in the blanks below to describe immunity.  

Define the key terms of the immune system. 

Column A

Column B

Antigens
Molecules on the surface of cells and pathogens
Antibody
White blood cells that stay in the blood after inf...
White blood cell
The ability to produce antibodies against a pathog...
Immunity
Protein molecule made by white blood cell to fight...
Memory cell
Cells in the blood that are part of the immune sys...

Emma has chickenpox. She doesn't mind though as she gets to miss school for a few days!

After Emma has been infected with the chickenpox virus, some of the white blood cells that made antibodies against it stay in her blood.

 

What are these cells called that stay in Emma's blood?

Antibodies

Memory cells

Red blood cells

  • Question 1

What are some of the physical barriers the body uses as defence against invading pathogens?
 

Image of bacteria, virus and fungi

CORRECT ANSWER
Skin
Mucus lining the airways
EDDIE SAYS
Were you tempted to tick them all? You are correct that all four of the options above are means of defence that our body uses against harmful microorganisms. However, only the skin and the mucus are physical barriers. Don't forget that stomach acid and enzymes are a chemical barrier, rather than a physical one.
  • Question 2

What chemical barriers protect the body from invading pathogens?

CORRECT ANSWER
Enzymes found in the mouth and eyes
Stomach acid
EDDIE SAYS
Hopefully, you will have worked out from the previous question that it must be the other options this time! Anything to do with acid and enzymes, think - chemical defence! The skin and mucus options are describing physical barriers.
  • Question 3

Pathogen cells have markers on their surface.

 

What are these markers called? 

 

Image of bacteria, virus and fungi

CORRECT ANSWER
antigen
antigens
EDDIE SAYS
It is always harder when you have no options to choose from. How did you get on with this one? To help you remember: Antigens and pathogens both end in the letters gen!
  • Question 4

Pathogens have markers on their surface called antigens.

 

What is the name of the protein that white blood cells make to fit the antigens?

 

Image of HIV virus attacking cells

CORRECT ANSWER
Antibody
EDDIE SAYS
It can get confusing with all these new terms! Antigens are markers on pathogens. White blood cells produce antibodies that lock on to the antigens like a jigsaw puzzle and make it easier to spot the harmful pathogens. Antitoxins can also be produced by white blood cells to neutralise toxins produced by the pathogens.
  • Question 5

Some white blood cells surround pathogens and engulf them. Once engulfed, the white blood cell destroys the pathogen.

 

What does the white blood cell contain that destroys the pathogen?

CORRECT ANSWER
Enzymes
EDDIE SAYS
How's it going? Even if you weren't confident with this one, you might have been able to eliminate the two incorrect answers - energy and glucose. Remember that it is sometimes possible to work out the correct answer to a question using a mixture of common sense and a process of elimination. Enzymes break down the cell wall of the pathogen and then destroy it.
  • Question 6

Hydrochloric acid is found in the stomach.

 

Why might this be a useful barrier against infection? 

 

Image of food

CORRECT ANSWER
The strong acid can destroy any pathogen found in food and drink
EDDIE SAYS
Don't worry if you got this one wrong. It was very tempting to go for the third option, wasn't it? The acid in the stomach does indeed help to start the process of breaking down food, by triggering the release of the enzyme, pepsin. However, careful reading of the question might have showed you that this is not an explanation as to how the acid prevents infection! Food poisoning is caused by bacteria found in food. The acid can help to destroy the pathogens if they reach your stomach.
  • Question 7

White blood cells make antibodies with shapes that fit the antigens. Other white blood cells can then find and destroy the microorganisms.

The diagram below shows the measles virus.

(These are not the real shapes or sizes of the pathogen or antigen!).

 

Which antibody -  A, B or C -  will match up with the measles' antigens?

 

 

Image of measles pathogen    Image of antigens

 

CORRECT ANSWER
A
EDDIE SAYS
How are your jigsaw puzzle skills?! A will fit the measles' antigen, just like a puzzle!
  • Question 8

Fill in the blanks below to describe immunity.  

CORRECT ANSWER
EDDIE SAYS
Immunity is all about how memory cells help to protect us from getting ill in the future! This is how vaccinations work. If we have had a vaccination against a disease, memory cells in our bodies have learned how to deal with the disease and can respond quickly if they meet it again.
  • Question 9

Define the key terms of the immune system. 

CORRECT ANSWER

Column A

Column B

Antigens
Molecules on the surface of cells...
Antibody
Protein molecule made by white bl...
White blood cell
Cells in the blood that are part ...
Immunity
The ability to produce antibodies...
Memory cell
White blood cells that stay in th...
EDDIE SAYS
Did you get them all correct? This is an excellent activity for you to consolidate and test your knowledge. Why not have a few tries if you're not completely confident with them? Well done - another activity completed!
  • Question 10

Emma has chickenpox. She doesn't mind though as she gets to miss school for a few days!

After Emma has been infected with the chickenpox virus, some of the white blood cells that made antibodies against it stay in her blood.

 

What are these cells called that stay in Emma's blood?

CORRECT ANSWER
Memory cells
EDDIE SAYS
How did you do? Antibodies are produced by white blood cells to help to destroy pathogens in the body, but it is the memory cells that help her body to recognise the chickenpox pathogen should she develop the disease again. Memory cells form a vital part of our immune systems. They help to protect us if we get infected by a pathogen a second time.
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