The immune system

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  • Created by: Laelle
  • Created on: 11-04-16 19:21
What is a non-specific response?
An immediate response to a pathogen, that is indiscriminate-the same for all
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Which mechanisms are non-specific?
Physical/chemical barriers + phagocytosis
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Which mechanisms are specific?
Cell-mediated immunity + the humoral response
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What characteristics do specific mechanisms have?
Slower responses + specific to each pathogen
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What is an infection?
An interaction between a pathogen and the body's defence mechanisms
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What is a pathogen?
A micro-organism that causes disease
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What is immunity?
The ability of an organism to resist infection by protection against a pathogen
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What are lymphocytes?
A type of white blood cell responsible for the immune response
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What activates lymphocytes?
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What identifies cells?
Molecules on their surface; in particular proteins
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What about proteins make them important for cell recognition?
Their 3-D and highly specific tertiary structure
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Why is it important that lymphocytes can identify self from non-self cells?
So they don't destroy the organisms own tissues
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Protein molecules allow lymphocytes to identify what?
Pathogens, non-self material (from other individuals of the same species), toxins, abnormal cells
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Implications of cell recognition?
Transplanted tissues/organs may be rejected by immune system
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How many types lymphocytes already exist?
10 million
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Why don't lymphocytes need to be produced in response to an infection?
Because there are so many types, there will be at least 1 that is complementary to a pathogen
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Why is there a time lag between exposure to a pathogen + overcoming it?
Because when a lymphocyte with receptors complementary and fit the proteins on the pathgoens surface, it is stimulated to divide by clonal selection to build their numbers to a level effective to destroy the pathogen
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Self cells are recognised where?
In the fetus
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Self-antigens are recognised where?
In adults, in the bone marrow
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What happens if a lymphocyte has a receptors that fit the bodys cells proteins?
It is suppressed or undergoes apoptosis
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So the remaining lymphocytes...
Have receptors that may fit foreign, non-self material and will respond to these
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What happens in adults if a lymphocyte has receptors that fit self-antigens?
It undergoes apoptosis before it can differentiate into a mature lymphocyte
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Apoptosis prevents...
Clones of the anti-self lymphocytes appearing in the blood
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If the first line defence (physical/chemical barriers) fail, what occurs next?
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What is a phagocyte?
A type of white blood cell that engulfs and digests pathogens
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What is formed when the pseudopodia membranes fuse together?
A vesicle, enclosing the pathogen forming a phagosomes
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What do lysozymes do to pathogens?
They hydrolyse them
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What happens after the pathogen is digested?
The phagocyte absorbs its products + displays some of its antigens on their own cell-surface membrane
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What does this activate?
T-cells (T lymphocytes)
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What is an antigen?
A protein molecules on the cell-surface membrane of an organism. It triggers an immune response by lymphocytes
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What do T-lymphocytes respond to?
an organisms own cells, infected by a non-self material from a different species
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Why do lymphocytes also respond to other organisms of the same species?
Because they are genetically different so have different antigens from self cells
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What are antigen-presenting cells?
Cells that display foreign antigens on their own cell-surface membrane
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Cell-mediated immunity is also known as?
The cellular response
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What do antigens ONLY respond to?
Antigen-presenting cells (foreign antigens presented on body cells)
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Are the receptors on T cells specific to an antigen?
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When a helper T cell attaches to an antigen what happens?
The specific helper T cell divides rapidly by mitosis producing clones
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What do the cloned Helper T cells do?
Develop into memory cells, stimulate phagocytosis + B cells to divide & secrete their antibody + activate cytotoxic T cells
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How do cytotoxic T cells kill infected cells?
Produce perforin- makes holes in C.S.M + makes its freely permeable
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Why are T cells action most effective against viruses?
Viruses replicate in host cells. By killing body cells, it prevents the viruses from multiplying + infecting more cells
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What is the next phase of the immune response?
Humoral Immunity
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What do T cells produce that stimulates B cells to divide and secrete their antibody?
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What do cytokines?
It stimulates B cells to divide and secrete their antibody
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It's called 'humoural' response because..?
It involves antibodies, that are soluble in the blood and tissue fluid
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What does clonal selection account for?
The body's ability to respond rapidly to a vast number of antigens
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Why are the clones produced referred to as monoclonal antibodies?
Because each clone is identical
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What do the clone cells develop into?
Plasma cells + memory cells
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What is the primary immune response?
The production of plasma and memory cells
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Other cards in this set

Card 2


Which mechanisms are non-specific?


Physical/chemical barriers + phagocytosis

Card 3


Which mechanisms are specific?


Preview of the front of card 3

Card 4


What characteristics do specific mechanisms have?


Preview of the front of card 4

Card 5


What is an infection?


Preview of the front of card 5
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