There are a lot of key players in the immune system. However for now, we’ll only focus on the key players and their role.
Immune cells
Let say, you get a cut on your finger. Your first line of defence (skin) has been broken. Now the bacteria is under the skin and in the body. Lysosomes in your tears are also part of the first line.
You need something to kill the bacteria before they start multiplying, spreading, creating toxins and killing healthy cells.
The next line of defence are your white blood cells. Your Macrophages are first on the scene to eat the bacteria.
Macrophages are blob like cells which engulf the pathogen and dissolve it. They also release chemicals which cause the body to release water and fluid to the scene (inflammation).
During the battle in your body, the battle field (cut) becomes filled with the dead bodies of your white blood cells, damaged body cells and dead bacteria cells.
This creates pus. As more and more bacteria are killed inflammation and pus gradually decrease until the tissue is completely healed.
Lets say that your macrophages weren’t enough. They are working as hard as they can, but they can’t seem to kill all the bacteria being produced.
What now?
Now we call in the heavy artillery. We use our last (3rd) line of defence. The specific immune system, capable of destroying specific viruses and bacteria.
The video shows a T cell killing a cancer cell.
Like we said, our last line of defence is specific, meaning each cell in this line, can only attack a specific virus or specific bacteria.
The way we activate this part of the immune system is by presenting the cells with antigens from the pathogen.
An antigen is a piece of the pathogen.
Specific white blood cells, called B cells produce antibodies.
These antibodies attach to the antigen marker on the pathogen and stops them from replicating, hold them together and signals to macrophages to eat them.
Every different antigen requires a different antibody.
The best part about the immune system, is its memory. Once your body fights an infection you create memory cells, which are left behind after the battle.
This means next time the same pathogen enters your body, your immune system will have a much larger and quicker response, so you’ll barley feel anything.
This means you are Immune.
So why is it then, you need a new flu shot every year?
This is because viruses and bacteria have a very high mutation rate. This means the flu that was here last year, is not the same flu as this years.
Since they mutate, their antigen markers change, meaning you need new antibodies to fight the infection.
Quick Questions
1.Give 2 examples of the first line of defence
2. How does a macrophage kill bacterium?
3. What causes inflammation?
4. How does pus form?
Quick Questions
1. What is unique about the third line of defence
2. Where is an antigen found?
3. What type of cells produce antibodies and how do antibodies affect bacterium?
Quick Questions
1. Explain how being infected, and beating the pathogen leads to immunity.
2. Explain how mutations help pathogens
Questions
Short Answer Questions
1. Draw an antigen and an antibody
2. Briefly describe the 1st, 2nd and 3rd lines of defence
3. Explain why different antibodies have to be made for every MOs
4. Create a Booklet or Poster to illustrate how a bacterium infects your body and how your body defeats it. Illustrate all the way to the 3rd line of defence and immunity.
