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Title: Immunity
Description: Covers some basic information on the Immune System - the function of T-cells and B-cells as well as stating definitions and key words as well as exemplar exam-question answers.
Description: Covers some basic information on the Immune System - the function of T-cells and B-cells as well as stating definitions and key words as well as exemplar exam-question answers.
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The Immune System
Immunity: the means to which the body protects itself from infection
Antigen: A foreign molecule/glycoprotein (usually a protein) that triggers an immune
response in the body
...
Epidermis of skin is dead / keratinised so pathogens cannot penetrate;
mucus in respiratory system is trapping sticky pathogens;
cilia move fluid / mucus removing pathogens;
tears / saliva / mucus contain lysozyme breaking down bacterial cell wall;
stomach contains hydrochloric acid which destroys bacteria;
blood clot prevents entry;
fluid nature of tears wash away bacteria;
vaginal acid destroys bacteria;
commensal bacteria on skin compete with pathogen;
sebum (fatty acid) inhibits bacterial growth;
Describe the role of phagocytes in the destruction of pathogens:
o The phagocyte recognizes the foreign antigen
o The cytoplasm of the phagocyte engulfs the pathogen, moving around it
o Pathogen is now contained in a phagocytic vacuole
o A lysosome fuses with the phagocytic vacuole and hydrolytic digestive enzymes
(lysozymes) are released and break down the pathogen
...
Response of T-‐lymphocytes (a type of white blood cell) to a foreign antigen (cell-‐mediated
immunity):
o Pathogens invade body cells/taken in by phagocytes
o The phagocyte places antigens from the pathogen on its cell-‐surface membrane
o Receptors on a specific helper T cell fit exactly onto these antigens
o This attachment activates the T cell to divide rapidly by mitosis and form a clone of
genetically identical cells
o The cloned T cells develop into memory cells (that enable a rapid response to future
infections by the same pathogen), activate cytotoxic T cells, stimulate B cells to
divide (which secrete antibodies) and stimulate phagocytes
...
Explain the role of B-‐lymphocytes and T-‐lymphocytes in the defence of the body against a virus infection
...
Antibody structure:
-‐ Antibodies are proteins, made of four polypeptide
chains with heavy and light chains
-‐ Specificity of antibody depends on its variable regions
(which form the antigen binding site)
-‐ Each antibody has a variable region with a unique tertiary
structure (due to different sequences of amino acids) that’s
complementary to one specific antigen
-‐ All antibodies have the same constant regions
Antibodies lead to destruction of the antigen; they do not destroy the
antigen themselves
...
Antibodies are protein molecules
...
Large variety of
different
Cellular response: The T-‐cells and other immune system cells e
...
phagocytes that they
molecules;
interact with
range of shapes;
Humoral Response: B-‐cells, clonal selection and the production of monoclonal Tertiary shape;
antibodies locks onto /
complements
specific antigen;
Destruction of pathogen/cells & antibody production:
o Monoclonal antibodies bind to the antigens on the surface of a pathogen to form
lots of antibody-‐antigen complexes
...
Targeting medication to specific-‐cell types
• Monoclonal antibodies specific to antigens on cancer cells are given to a patient and
attach themselves to the receptors on a cancer cell
• They attach to the surface of their cancer cells and block the chemical signals that
stimulate uncontrolled growth
...
Pregnancy Testing
Placenta produces a hormone called HCG found in the mother’s urine – monoclonal
antibodies present on the test strip are linked to colored particles – if HCG is present in the
urine it binds to these antibodies forming a HCG antibody-‐color complex moving along the
strip creating a colored line
...
action of phagocytes;
Interferon production;
body temperature increased;
ref to B or T lymphocytes;
activated by non-‐self-‐antigen;
either clone / divide by mitosis;
T helper cells role;
B plasma cells produced;
which produces antibodies;
any specific effect (e
...
immobilise /agglutinate / lysis /coat for recognition /
neutralise toxins);
T killer / cytotoxic cell;
perform produced;
memory cell produced;
Clonal Selection: each lymphocyte has immunoglobulin receptors specific for a particular
antigen and after the receptor is engaged, plasma cells are produced
...
Active Immunity: when your immune system makes its own antibodies after being
stimulated by an antigen
...
Passive Immunity: immunity by being given antibodies from a different organism – your
immune system doesn’t produce any antibodies of its own
Natural Passive Immunity: when a baby becomes immune from the antibodies it
receives from it mother via the placenta/breast milk
...
Vaccines protect people against disease
...
(5)
1
...
From dead pathogens / weakened pathogens;
3
...
On second exposure memory cells produce antibodies / become active / recognise pathogens;
5
...
Antibodies destroy pathogens;
7
...
Suggest why there
might be problems for the patient when using these vaccines
...
consider vaccines to be unsafe / have side effects / damage immune system;
consider natural immunity to be more effective; allow in (a) if not here
religious / ethical objections qualified e
...
objections to use of fetal /
animal tissue;
consider low risk of disease when high percentage of population already
vaccinated/Ref
...
Killed microorganism;
modified toxin;
attenuated/heat treated/UV treated microorganism;
genetically engineered antigens;
isolated antigen
Vaccines protect against disease by stimulating the production of memory cells
...
On further exposure to same microorganism;
Antigen recognised;
Faster response;
Greater production of antibodies;
State two differences between a specific and non-‐specific defence mechanism
Response is slow for specific defence mechanisms whereas it is immediate for non-‐specific defense mechanisms
...
It takes a few days for the lymphocytes complementary to the antigens on the pathogen to divide and build up to
the level where it can be effective at destroying the pathogen – hence the time lag between the exposure to the
pathogen and the body’s defenses at bringing it under control
...
Explain why the secondary immune response is much more rapid than the primary response
Contrast the cell-‐mediated response to the humoral response
Non-‐Specific
Defences
Mechanisms that don’t distinguish between one type of pathogen
or another e
...
skin
Specific Defences
Mechanisms that do distinguish between different
pathogens e
...
lymphocytes
Phagocytosis
Pathogens are engulfed into vesicles (called phagosome)
and broken down by enzymes
Part of an organism that is recognised as non-‐self and
triggers an immune response (usually they are proteins)
T lymphocytes recognise antigen-‐presenting cells that
have been invaded and undergo mitosis to respond
Immunity involving B cells and antibodies
Antigens
Cell-‐mediated
Immunity
Humoral
Immunity
Antigenic
Variability
Antibodies
Antigen-‐Antibody
Complex
Complementary
Shape
Monoclonal
Antibodies
Passive Immunity
Active Immunity
Vaccination
Herd Immunity
Viruses such as flu have many different strains with
different antigens on them
Proteins synthesised by B cells, consisting of heavy and
light chains and variable and constant regions
Formed when antigens bind to a specific site on the
antibody
Antigens have a shape that means they fit into their
specific antibody
Isolation and cloning of a single type of antibody
The introduction of antibodies from an outside source
Stimulation of antibody production by the individual’s
own immune system
The introduction of a substance into the body with the
purpose of stimulating active immunity against a
particular disease
Vaccinating most of a population so that no-‐one has the
disease and transmission is stopped
Title: Immunity
Description: Covers some basic information on the Immune System - the function of T-cells and B-cells as well as stating definitions and key words as well as exemplar exam-question answers.
Description: Covers some basic information on the Immune System - the function of T-cells and B-cells as well as stating definitions and key words as well as exemplar exam-question answers.