AQA AS unit 1 notes on the immune system and immunology

AQA, unit 1 

includes full notes on immunology, pathogens and the immune system

this is a tricky topics for me and so I used all the sources available to me to compile these notes

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The Immune system
1. Pathogens cause infectious disease:
A pathogen is an organism that causes disease. The pathogen could be a micro-organism (bacteria, viruses
or fungi) or other organisms (tapeworm)
2. Pathogens enter the body by:
Break in the skin
3. How pathogens effect the body:
Damage the gas exchange surface
Air containing pathogens is breathed in
Pathogens are trapped in the mucus of the epithelium
The cilia move the mucus up the trachea to the mouth
However, some pathogens make it to the alveoli
Damage the skin
Pathogens enter through a break in the skin
They enter into the blood stream
The blood clots at the damage to try and prevent more pathogens entering
However a few pathogens enter before the blood clot is fully formed
Damage the digestive system
Food or drink containing pathogens is ingested
Pathogens are destroyed in the HCl acidic conditions of the stomach
However, some pathogens make it to the small intestine and invade the cells of the gut wall
4. What do pathogens do:
Produce toxins ­ bacteria release toxins
Damage cells ­ viruses replicate inside of cells and so they rupture
Ruptures the cells to release nutrients for their own use which starves the cell and so it
eventually dies
5. Line of defence, when a pathogen enters:
Non-specific responds to all micro-organisms Physical barrier
Specific responds to specific micro-organisms B-Lympocytes

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6. Non-specific responses:
Outside Inside
Barrier (eg. Skin) Blood clot Pathogens inside
the body
Pathogens (eg. Bacteria)
Lysosome in sweat Inflammation Phagocytosis
7. Immune response
Body temperature rises ­ damages pathogenic cells
Inflammation ­ due to the blood vessels in the affected area become more permeable and so more white
blood cells and antibodies can come to the infected area
8.…read more

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B-cells release antibodies
Antibodies attack the pathogen
10. Phagocytes activate t-cells:
A t-cell is another type of white blood cell
It has complementary antibodies on the surface that bind to the antigens (from phagocytosis)
What the t- cells do:
Divide by mitosis to form clones
Release substances to activate the B-cells
Some attach to the antigens on a pathogen and kill the cell
11.…read more

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Primary and Secondary response:
An antigen enters the body for the first time
Activates the immune system ­ primary response
There aren't many b-cells so few antibodies can bind to them and so it's slow
Eventually the b-cells are replicated into plasma cells and so there are enough antibodies to
overcome the infection
The t-cells and b-cells produce memory cells They remain in the body for a long time
Memory t-cells remember the specific antigen
Memory b-cells remember the specific antibodies
If the same pathogen…read more

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Vaccines contain either a pathogen or their antigens
They stimulate primary response so that when the actual pathogen is encountered, the secondary
response is strong enough to prevent the disease developing
Types of vaccine:
Live vaccines
The pathogens in the vaccine are treated so they only divide a few times, and don't create
the infection
Eg. Mumps, rebella
Dead micro-organisms
They don't cause the disease but contain the antigens to stimulate an immune response
Eg. diptheria
Purified antigens
Made by genetic engineering
Eg.…read more

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They are produced from a single group of genetically identical b-cells (plasma cells)
They are very specific (their binding sites have a unique structure that only one antigen will be
complementary to)
They will bind to anything ­ an antigen or another substance as they will target and only bind to this
18.…read more



Really helpful just a lot of spelling mistakes

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