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NON SPECIFIC DEFENCE MECHANISMS
Do not distinguish between one pathogen and another. Either a barrier to stop entry of pathogens
Do distinguish. Less rapid response but it provides long lasting immunity. The response involves a
lymphocyte (type of white blood cell). Either a cell mediated T lymphocyte response or humoral B
RECOGNISING OWN CELLS
Each lymphocyte is capable of recognising a different chemical shape.
When lymphocytes collide with other cells, they recognise if it's an own body cell or a foreign cell.
Some lymphocytes will have receptors that exactly fit those of own body cells.
Others fit foreign cells only.
BARRIERS TO ENTRY
Protective covering- e.g. skin. Physical barrier.
Epithelia covered in mucus
Hydrochloric acid in stomach- low pH so enzymes of most pathogens are denatured.
Large particles, e.g. bacteria, that are too big to diffuse/AT across cell-surface membrane, are
1. Chemoattractants cause phagocytes to follow
2. Phagocytes attach themselves to the surface of the pathogen
3. They engulf the pathogen to form a phagosome (a vesicle)
4. Lysosomes move towards the vesicle and fuse with it
5. Enzymes in the lysosome break down the pathogen.
6. The soluble products are absorbed into cytoplasm of the phagocyte.
Phagocytosis causes inflammation at the site of infection. Pus contains dead pathogens and
phagocytes. Inflammation is the result of histamine which causes dilation of the blood vessels,
which speeds up delivery of phagocytes to site of infection.
An antigen is a protein that is recognised as foreign/non-self by the immune system and stimulates
an immune response
Antigens are usually a part of the CSM or cell walls of invading cells.
T LYMPHOCYTES CELL MEDIATED IMMUNITY
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T lymphocytes mature in the Thymus gland and produced in the bone marrow.
T lymphocytes respond to an own cell that has been invaded by non-self material.
T lymphocytes can distinguish own cell/foreign cell with phagocytes that have engulfed and
broken down a pathogen display pathogens antigens on CSM called antigen-presenting
cells. Also body cells invaded by virus also display antigens.
T cells kill infected cells by punching a hole in the cell, making the cell freely permeable.
Stages of response:
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Antigens of viruses are constantly changing.
Our antibodies or memory cells will not correspond with new shape of the virus so only the primary
immune response can overcome the infection.
We therefore develop symptoms.
Antibodies are proteins synthesize by B cells.
Antibodies are made of four polypeptide chains.
One pair of polypeptide chains are heavy chains, other are light chains.
Light chains can change shape to help antigen fit.
Antigen-antibody complex is formed.…read more
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Immunity introduced by the antibodies to an individual from an outside source.
Active immunity is produced by stimulating the production of antibodies in the individuals own
Vaccination is the introduction of a substance into the body to stimulate active immunity against a
Features of a successful vaccination programme...
Economically available in large quantities
Few side effects
Easily produced, stored, transported
Good means of administrating the vaccine at appropriate times
Vaccinate a vast majority of vulnerable population.…read more