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Discuss 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. It can do this in places such as 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 goblet 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 further prevent infection. So what are these chemical barriers?

 

Image of eye

 

Enzymes called lysozymes 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 called 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 called phagocytes recognise these foreign antigens and will engulf and destroy these pathogens. This process is called phagocytosis.

Other white blood cells called lymphocytes, make proteins called antibodies that fit the antigens of a pathogen like a puzzle. Antibodies neutralise pathogens in a number of ways: 

They bind to pathogens' antigens and damage or destroy them.
They coat pathogens, clumping them together so that they are easily ingested by phagocytes.
They bind to the antigens of the pathogens and release chemical signals to attract more phagocytes.

Some pathogens will produce toxins that make you feel ill. Lymphocytes may also release antitoxins that will stick to the appropriate toxin and stop it damaging the body.

 


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 lymphocytes.

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

Your body destroys the pathogen before it can make you ill.


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

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

The diagram 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.

Toxins produced by pathogens can make us feel ill.

 

How do white blood cells respond to toxins? 

Lymphocytes produce antibodies which bind to the pathogen and neutralise it

Lymphocytes produce antitoxins which bind to the pathogen and neutralise it

Lymphocytes produce toxins which bind to the pathogen and neutralise it

Our eyes produce tears.

 

How do tears act as a defence against pathogens?

Lymphocytes produce antibodies which bind to the pathogen and neutralise it

Lymphocytes produce antitoxins which bind to the pathogen and neutralise it

Lymphocytes produce toxins which bind to the pathogen and neutralise it

 

The immune system can recognise normal cells as well as pathogens.

 

How does the immune system do this? 

 

Receptors on white blood cells recognise and bind with the pathogen's antigens

 Receptors on white blood cells recognise the pathogen's antibodies

Receptors on the pathogen recognise the body's antigens

 

There are a number of ways that antibodies produced by white blood cells can destroy pathogens.

 

Match the sentences below to show how antibodies destroy pathogens.

Column A

Column B

Antibodies can bind to the antigens on the pathoge...
...and can directly damage or destroy them
Antibodies can bind to the antigens and coat path...
...attract more phagocytes which will ingest the p...
They bind to the pathogens and release chemical si...
...clumping them together so that they are easily ...

 

The human body has many defences against invading pathogens.

 

Place the defences into the correct columns below.

 Physical defenceChemical defence
Hydrochloric acid in the stomach
Ciliated cells in airways
Mucus produced by goblet cells in lungs and airways
Lysozyme in eyes and mouth
Skin covering the body
Nose hairs

Liam had food poisoning after eating an undercooked burger. The graph shows the concentration of antibodies in his blood following exposure to the salmonella bacteria that caused his food poisoning.

 

What happens to the concentration of antibodies in his blood after being exposed to salmonella for the first time?

 

Image of graph showing antibody concentration in blood

The concentration of antibodies in Liam's blood rose slowly to its peak at around 80 days

The concentration of antibodies in Liam's blood rose slowly to its peak at around 30 days

The concentration of antibodies in Liam's blood rose slowly to its peak at around 25 days

 

Liam had food poisoning after eating an undercooked burger. The graph shows the concentration of antibodies in his blood following exposure to the salmonella bacteria that caused his food poisoning.

 

How does the concentration of antibodies in his blood after a second exposure to the bacteria compare with the first exposure?

 

Image of graph showing antibody concentration in blood

 

The second exposure to the bacteria produces a much higher concentration of antibodies in the blood in comparison to the first exposure

The second exposure to the bacteria produces a much lower concentration of antibodies in the blood in comparison to the first exposure

The second exposure to the bacteria produces the same concentration of antibodies in the blood as the first exposure

Liam had food poisoning after eating an undercooked burger. The graph shows a sharp rise in antibody concentration after being exposed to the same bacteria a second time.

 

Why does Liam's body produce a higher concentration of antibodies the second time around?

 

Image of graph showing antibody concentration in blood

After the first exposure to the bacteria, memory lymphocytes are broken down

After the first exposure to the bacteria, memory lymphocytes remain in Liam's blood

On the second exposure, the memory lymphocytes replicate and are able to produce a higher concentration of antibodies

On the second exposure, the memory lymphocytes stop replicating

  • Question 1

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

The diagram 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
A will fit the measles antigen a bit like a puzzle!
  • Question 2

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 3

Toxins produced by pathogens can make us feel ill.

 

How do white blood cells respond to toxins? 

CORRECT ANSWER
Lymphocytes produce antitoxins which bind to the pathogen and neutralise it
EDDIE SAYS
You need to read the three options very carefully here! Lymphocytes do indeed produce antibodies, but these lock on to antigens on pathogens - they don't neutralise toxins. Toxins are neutralised by antitoxins produced by lymphocytes.
  • Question 4

Our eyes produce tears.

 

How do tears act as a defence against pathogens?

CORRECT ANSWER
EDDIE SAYS
Don't worry if you didn't get all these correct - it is hard to get the exact word needed sometimes! Just have another go and see if you can get them all right next time. Enzymes destroy the pathogens that enter the eyes or mouth, pretty useful right?!
  • Question 5

 

The immune system can recognise normal cells as well as pathogens.

 

How does the immune system do this? 

 

CORRECT ANSWER
Receptors on white blood cells recognise and bind with the pathogen's antigens
EDDIE SAYS
You need to read these three options very carefully because there is only a small difference in the wording of two of them! The first option was the correct one this time. The receptors on the white blood cells recognise the antigens on a pathogen and bind to them like a jigsaw puzzle fitting together. A pathogen's antigens are almost like a bright flashing signal that white blood cells look out for, it signifies an invasion!
  • Question 6

 

There are a number of ways that antibodies produced by white blood cells can destroy pathogens.

 

Match the sentences below to show how antibodies destroy pathogens.

CORRECT ANSWER

Column A

Column B

Antibodies can bind to the antige...
...and can directly damage or des...
Antibodies can bind to the antig...
...clumping them together so that...
They bind to the pathogens and re...
...attract more phagocytes which ...
EDDIE SAYS
It all sounds very complicated but it is actually as easy as doing a jigsaw puzzle! Antibodies bind with antigens found on the pathogen. It's what happens following binding that determines how the pathogen is destroyed! Having made the pathogens clump together, the phagocytes can engulf and then ingest them.
  • Question 7

 

The human body has many defences against invading pathogens.

 

Place the defences into the correct columns below.

CORRECT ANSWER
 Physical defenceChemical defence
Hydrochloric acid in the stomach
Ciliated cells in airways
Mucus produced by goblet cells in lungs and airways
Lysozyme in eyes and mouth
Skin covering the body
Nose hairs
EDDIE SAYS
This would be a good task for revision or for an extended response in an exam question as it allows you to compare both easily. Did you manage to sort them into their correct columns? The key to remembering which is which is that physical defences are to do with an actual physical barrier, whereas chemical defences need to be produced by the body in the form of acid or enzymes.
  • Question 8

Liam had food poisoning after eating an undercooked burger. The graph shows the concentration of antibodies in his blood following exposure to the salmonella bacteria that caused his food poisoning.

 

What happens to the concentration of antibodies in his blood after being exposed to salmonella for the first time?

 

Image of graph showing antibody concentration in blood

CORRECT ANSWER
The concentration of antibodies in Liam's blood rose slowly to its peak at around 25 days
EDDIE SAYS
How did you do? Don't get confused, the question is referring only to the first exposure. The levels of antibodies in his blood rises slowly during his first exposure to the bacteria. It reaches a peak at around 25 days, before dropping off again.
  • Question 9

 

Liam had food poisoning after eating an undercooked burger. The graph shows the concentration of antibodies in his blood following exposure to the salmonella bacteria that caused his food poisoning.

 

How does the concentration of antibodies in his blood after a second exposure to the bacteria compare with the first exposure?

 

Image of graph showing antibody concentration in blood

 

CORRECT ANSWER
The second exposure to the bacteria produces a much higher concentration of antibodies in the blood in comparison to the first exposure
EDDIE SAYS
If you study the graph above, you can see a big difference in the concentration rates. After the second exposure, you can see a steep rise on the graph. It reaches higher than after the first exposure, showing that more antibodies have been produced.
  • Question 10

Liam had food poisoning after eating an undercooked burger. The graph shows a sharp rise in antibody concentration after being exposed to the same bacteria a second time.

 

Why does Liam's body produce a higher concentration of antibodies the second time around?

 

Image of graph showing antibody concentration in blood

CORRECT ANSWER
After the first exposure to the bacteria, memory lymphocytes remain in Liam's blood
On the second exposure, the memory lymphocytes replicate and are able to produce a higher concentration of antibodies
EDDIE SAYS
Have you got this sorted yet? This is testing your understanding of how immunity works. After the second exposure, more antibodies are produced due to the fact that there are memory lymphocytes in the blood. They quickly recognise the bacteria the second time around and rush to produce many more antibodies quickly. This is how vaccination works. If you are given an immunisation vaccine against a disease, such as measles, your body is able to learn how to deal with the pathogen before it meets the disease itself. Memory lymphocyte cells are then able to produce antibodies to deal with quickly if it ever becomes necessary. Well done for completing another activity!
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