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CELL IMMUNITY notes A* , AQA biology summarised notes
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Used for revision/ learning. Encompasses all ideas in TOPIC 2 of AQA Biology (cell immunity). These revision notes got me an A*
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🗡️cell immunity
defence mechanisms
immune system: system of biological structures and processes within an organism
that protects against disease by identifying and killing pathogens (and tumour cells)
pathogen: disease-causing microorganism
antigen:
a protein or glycoprotein found on surface of cell membrane and foreign material that
indicate to the immune system if it is "self" or "non-self"
any non-self substance capable of triggering an immune response is known as an
antigen
primary line of defence
initial reaction to infection:
inflammation is the response to cell damage- this is redness, swelling, pain
and raised temperature. this happens to encourage non-specific immune
cells into area (increased blood flow).
temperature also increases to try and reduce pathogenic load because
microorganisms may have proteins that are denatured/ functioning less
optimally at a higher temperature
response is immediate and same for all pathogens
physical barriers
non-specific
eyelashes and hairs→ trap pathogens
cell immunity 1
, skin
acts as barrier
pH of skin makes it less habitable for pathogenic organisms
natural skin flora will outcompete pathogenic organisms
skin keratinised so flakes off.
mucus → made by goblet cells and traps pathogens & foreign material, which
is then wafted up by ciliated epithelial cells (swallowed or coughed out)
stomach acid→ denature proteins in pathogen so they cannot function
wound healing → platelets clump together to fill in holes in skin
phagocytosis
non-specific
occurs when non-specific immune cells (macrophages, neutrophils) target
pathogens
0.5. phagocytes undergo chemotaxis (move towards chemical signature of
pathogen)
1. when encountering pathogen, will have receptors that recognise and bind to
non-self antigens. this triggers phagocyte to begin ingesting pathogen
1.5. phagocyte forms pseudopodia (legs) of cell membrane around the
pathogens— forming a vesicle called a phagosome [endocytosis]
2. phagosome joins with lysosome to form a phagolysosome
3. digestive enzymes within lysosome will destroy pathogen
4. usable bits are recycled and if phagocyte is an APC, pathogen's antigens will be
presented on cell surface membrane
secondary line of defence
response is slower and specific to each pathogen
triggering the response:
cell immunity 2
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