b6.3 - immune system Flashcards
ELISA test
sees if plant contains pathogen antigen
ELISA test method
- obtain + liquidise sample put into a plastic tube
- wash to wash off any proteins not bound to plastic
- add a blocking agent to block all plastic that has not been covered with protein
- wash again to revive unbound blocking agent
- add antibody enzyme complex that is specific to pathogens antigen
- wash again to remove unbound antibody enzyme complex
- add colourless substrate that the enzyme changes into a coloured product
- if pathogen is present it’ll change colour
primary immune defences
- skin
- mucous membranes
- blood clots
- respiratory surfaces
skin
keratin layer , epidermis, sweat gland, hair follicle, dermis, subcutaneous layer
- waterproof barrier that prevents pathogens from entering
commensalism bacteri
not harmful bacteria on the skin surface
- outcompete any pathogenic bacteria and fungi that may land on the skins surface
mucous membranes
nasal muscles traps air borne organisms
any that get past get trapped in the respiratory tract
- mucus is produced by goblet cells
- and is removed by cilia beating passing it to stomach where high acidity denatures it
- contains LYSOZYME which is an antibiotic and destroys pathogens
blood clots
- when skin is cute platelets are exposed to air
- cause a protein called FIBRINOGEN to change to fibrin (insoluble)
- fibrin forms a mesh over wound
- red blood cells are caught in the mesh - platelets stick together - form blood clots
- clot hardens to a scab keeping skin clean with time to heal
respiratory surfaces
- mucus secreted by goblet cells trap dust particles and microbes
- cilia beat and waft the mucus up to the top of the throat when swallowed
- cilia contain many mitochondria to supply the energy needed
types of white blood cells
- lymphocytes
- phagocytes
lymphocytes
- produce antibodies that destroy pathogens - some provide immunity
- similar size to red blood cells with a spherical nucleus
- 25% of white blood cells
phagocytes
- engulf bacteria and other microorganisms
(phagocytosis) - encloses bacteria in phagosome and digestive enzyme released to destroy bacteria
- relatively large cells, often with lobed nucleus (to allow it to engulf pathogens)
- ## 70% of white blood cells
antigens
- protein on the cell membrane of pathogens
- each pathogen has uniquely shaped antigens
- some pathogens (eg flu) may alter antigens yearly
antibodies
- are proteins made by lymphocytes
- have specific shape (3D) complementary to a specific antigen
- antibodies bind to antigens on the surface of pathogens
how lymphocytes bind to antigens
- each lymphocyte has antibodies specific to antigens
- when an antigen is in the blood a lymphocyte with complementary receptor will be found and will bind to it
- the appropriate lymphocyte then divides by mitosis
antibody structure
see diagram
- antigen binding site
- constant regions
- heavy chains
- light chains
- hinge
- variable parts ( change from antibody to antibody but dont change once its made)
how antibodies kill pathogens
cell lysis
agglutination
neutralisation
how antibodies kill pathogens - cell lysis
- may cause pathogens to burst open rendering them unable to infect our cells
how antibodies kill pathogens - agglutination
- antibodies may bind to a number of pathogens causing them to clump together
- the group of pathogens is too large to enter a cell and can be destroyed by phagocytes
how antibodies kill pathogens - neutralisation
- antibodies cover pathogens and prevent it from binding + entering a host
- antitoxins released from lymphocytes may also act on toxins released from pathogens rendering them ineffective
monoclonal antibodies
are specific to one binding site on one antigen - target a specific cell/ chemical
how many antibody types does a antigen make
one type of antibody specific to one antigen
why are lymphocytes combined with other cells to make monoclonal antibodies
it cant divide anymore so if we want lots of antibodies we need a cells that will divide
how to make monoclonal antibodies
- a mouse is infected with a specific antigen to stimulate lymphocytes to make particular antibodies
- extracted lymphocytes are combined with tumour cells that can divide and make antibodies (hybridoma cells)
- separated and each cell is cloned making cells that produce the same antibody
- antibodies are made, collected and purified
monoclonal antibodies uses
- for diagnosis
- in research
- to treat some diseases
monoclonal antibodies uses - for diagnosis
- pregnancy tests - monoclonal antibody binds to hCG in urine
monoclonal antibodies uses - in research
- mAB can locate or identify specific molecules in a cell/tissue
- these have fluorescent tags in them
- the mABs then bind the specific molecules in the cell
monoclonal antibodies uses - treat diseases
- for cancer mABs can be bound to a radioactive substance, a toxic drug/chemical- which stops cells growing or dividing
- it delivers the substance to cancer cells without harming healthy cells (specifically targeted)
concerns with monoclonal antibody uses
- immunes responses occur as they come from mice cells with foreign proteins
- side effects - chills/fever, itchy rashes, nausea, headaches
