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Communication between cells
Cell signalling
· Immune response involves co ­ ordinated response
between a range of cells, cells need to communicate, this is
known as cell signalling.
1. Communication is activated through the release of
hormone ­ like chemicals called cytokines.
2. For a signal to be detected the target cell needs an cell
surface receptor.
3. B cells and T cells have receptors that are complementary
to the antigen.
4. The antigen may be an isolated protein or it may be
attached to a pathogen.
5. When the antigen is detected the lymphocyte is activated.…read more

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Communicated information
Identification ­ Pathogen carries antigens, these act as markers and are
detected by our body cells.
Sending distress signals ­ The internal cell organelles use lysosomes to fight
the invader.
Pathogens end up attached to the host plasma membrane, e.g. they act as
distress signal and act as markers to indicate the cell is infected.
Antigen presentation ­ Macrophages act like phagocytes to engulf and digest
the pathogen. They separate out the antigens and expose them on the
surface of the macrophage, this becomes an antigen ­ presenting cell.
Instructions ­ Cytokines act as instructions to their target cells, they bind to
specific membrane ­ bound receptors on the target cell, this alter's the cell's
behaviour. Communication includes:
· Macrophages release monokines that attract neutrophils by chemo taxis.
· The monokines stimulate B cells to differentiate.
· T, B cells and macrophages release interleukins.
· Cells release interferon which inhibits virus replication and stimulates
activity of T killer cells.…read more

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The specific immune response
The immune response
· Specific response to the detection of
pathogens.
· Involves B and T cells.
· Produces antibodies, these neutralise the
foreign antigens.
· Produces immunological memory through the
release of memory cells.…read more

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Starting the response
· Lymphocytes carry the correct receptor molecules
on their membranes.
· The receptor molecules are cell surface proteins
that have a complementary shape to the antigen.
· Selection of B and T lymphocytes is known as
clonal selection.
· Before fighting of an infection lymphocytes
increase in what is known as clonal expansion.…read more

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Differentiation
· T lymphocytes differentiate into three different types
of cell:
- T helper cells release cytokines, B cells stimulate
phagocytosis.
- T killer cells attack and kill infected body cells.
- T memory cells
· B lymphocytes develop into the following:
- plasma cells which release antibodies
- B memory cells that act as immunological memory.…read more

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