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Biology- 4.1 Communicable Diseases > The Immune System > Flashcards

Flashcards in The Immune System Deck (33)
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What is an immune response?

Its the body reaction to a foreign antigen.


Whats an antigen?

Antigens are molecules (usually proteins or polysaccharides) found on the surface of cells.


What happens when a pathogen (like bacterium) invades the body?

when a pathogen (like bacterium) invades the body the antigens on its cell surface are identified as foreign, which activates cells in the immune system.


In what stages does the immune system respond?

The immune systems involves specific and non specific stages


How does the non specific response happen?

The non specific response happens in the same way for all microorganisms - whatever foreign antigens they have?


How does the specific response happen?

The specific response is antigen-specif - it is aimed at specific pathogens and involves blood cells called T and B lymphocytes


Whats the first stage of the immune system?

1. Phagocytosis


What's a phagocyte?

Its a type of blood cell that carries out phagocytosis (engulfment of pathogens)


Wheres a phagocyte found and was do they do?

They're found in the blood and in tissues and carry out a non-specific immune system.


How does a phagocyte work?

> A phagocyte recognises the antigens on a pathogen
> The cytoplasm of the phagocyte moves round the pathogen, engulfing it.
> The pathogen is no contained in a phagosomes ( a type of vesicle) in the cytoplasm of the phagocyte.
> A lysosome (an organelle that contains digestive enzymes) fuses with the phagosome. The enzymes break down the pathogen.
> The phagocyte then presents the pathogens antigen. It stick the antigen on its surface to activate other immune system cells. When a phagocyte does this its acting as an antigen presenting cell.


How can the the cytoplasm of the phagocyte moving round the pathogen, engulfing it can be made easier?

It can be made easier by the presence of opsonins - molecules in the blood that attach to foreign antigens to aid phagocytosis.


What are neutrophils?

its a type of pathogen and are the first white blood cells to respond to a pathogen inside the body


What do neutrophils do?

They move towards a wound in response to signals from cytokines (protein that act as messenger molecules). The cytokines are released by cells at the site of the wound.


What is T lymphocyte?

Its another type of white blood cells which is covered with receptors that bind to antigens presented by APCc


How does a T Lymphocyte work?

> Each T lymphocyte has a diff receptor on its surface therefore when it meets a complementary antigen, it binds to it.
> This process activates the T lymphocyte which is knows as clonal selection
> The activated T lymphocyte then undergoes clonal expansion - it divides to produce clones of itself.


Why do different types of activated T lymphocytes carry out different functions?

> T helper cells release substances to activate B lymphocytes and T killer cells
> T killer cells attach to and kill cells that are infected with a virus
> T regulatory cells suppress the immune response from other white blood cells. This helps to stop immune system cells from mistakenly attacking the hosts body cells.


What happens to some activated T lymphocytes?

They become memory cells


What are B lymphocytes?

They are a type of white blood cells which are covered with antibodies - proteins that bond antigens to form an antigen-antibody complex.


What type of antibodies do B lymphocyte have?

Each B lymphocyte has a different shaped antibody on its membrane l, so different ones bind to different shaped antigens


How do antibodies of B lymphocyte bind?

They meet a complementary antigen and bind to it. The substance released from helper T cells, activate the B lymphocyte. This process is another example of clinal expansion.


What happens to the activated B lymphocytes?

They divide by mitosis into plasma cells and memory cells. This is another example of clinal expansion.


What's are clones of B lymphocytes?

Plasma cells


What do plasma cells severely?

They decree loads of the antibody, specific to the antigen, into the blood.


What happen to the antibodies of plasma cells?

These antibodies will bind to the antigens on the surface of the pathogen to form lots of antigen-antibody complexes. This is the signal for the immune system to attack and destroy the pathogen.


What is cell signalling?

It's how cell communicate


What cause a response of some kind in the other cell?

A cell may release a substance that bind to the receptors on another cell which would cause a response in the other cell


Why is cell signalling important?

It's important in the immune system because it helps to activate all the different types of white blood cells that are needed


What do T helper cells release?

They release interleukins (a type of cytokine) that bind to receptors on B lymphocytes. This activates the B lymphocyte - the T helper cells are signalling to the B lymphocytes that there's a pathogen in the body


What are blood smears?

It's a sample of blood smeared over a microscope slide


How are red blood cells easy to spot?

They have no nucleus