Summary of the secondary defence, WBC, T CELLS, B CELLS etc.

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The immune response summarised
THE IMMUNE RESPONSE IS THE BODY'S REACTION TO A FOREIGN ANTIGEN ENTERING THE BODY.
Made up of non-specific (doesn't matter what the antigen is) and specific (only specific to certain
antigens on certain pathogens).
If the antigen gets past the primary defence (skin, tears etc.) then the secondary response begins.
1. PHAGOCYTOSIS (Non-specific)
1) A phagocyte is a type of white blood cell. It is found in blood and tissue.
2) The phagocyte RECOGNISES the antigens on pathogen.
3) The phagocyte's cytoplasm then surrounds the pathogen and engulfs it. OPSONINS CAN MAKE
THIS EASIER BECAUSE THEY ARE MOLECULES WHICH BIND THE ANTIGENS AND THEREFORE
AID PHAGOCYTOSIS.
4) The pathogen is now in a vesicle in the phagocyte called a phagosome.
5) Lysosomes in the phagosome fuse with the pathogen. They release digestive enzymes which
break the pathogen down.
6) The phagocyte then PRESENTS the antigens of the
pathogen on its surface. (Seen as a antigen presenting
cell)
7) This activates other immune system cells in the body.
2. T LYMPHOCYTE ACTIVATION (Specific)
1. These are another type of white blood cell.
2. Their surface is covered with RECEP TORS.
3. The receptors bind with antigens presented by antigen presenting cells.
4. Each T lymphocyte has different receptors on its surface and each one binds to different
antigens.
5. When a T lymphocyte receptor meets a complementary antigen then it binds to it.
6. This activates the T lymphocyte. This is known as clonal selection.
7. The activated T lymphocyte then divides into clones which then differentiate into different types of
T cell. This is known as clonal expansion.
The types of t cells which can be made are:
-T helper cells: these release substances which activate the B lymphocytes.
-T killer cells: these bind to the antigens on the pathogen and kill it.
-T regulatory cells: these supress the immune response to other white blood cells. Basically, they stop the
immune system cells from mistakenly attacking the host's body cells.
-Some are made into memory cells.
3. B LYMPHOCYTE ACTIVATION (Specific)

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The b lymphocytes are also another type of white blood cell.
2. Their surface is covered with ANTIBODIES.
3. Antibodies are proteins which bind with antigens to form antigen-antibody complexes.
4. Each B lymphocyte has a different shaped antibody so different ones bind to different
antigens.
5. When an antibody on a B lymphocyte meets a complementary antigen, they bind.
6. This, along with some of the substances released by T helper cells, activates the B
lymphocyte. (Clonal selection).
7.…read more

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