How do we eliminate pathogens that live inside cells?

Ifeoma Ezepue
Flashcards by Ifeoma Ezepue, updated more than 1 year ago
Ifeoma Ezepue
Created by Ifeoma Ezepue about 4 years ago
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University Fundamentals of Medicine (Immunology) Flashcards on How do we eliminate pathogens that live inside cells?, created by Ifeoma Ezepue on 11/04/2015.
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How do we kill infected cells? cytotoxic T cells (CD8+ T cells) NK cells macrophages
Describe the basics of the immune response DC pick up bits of infection internalize proteins and chop them up stick peptides onto MHC surface migrate to draining lymph nodes MHC displayed to T cells T cells activated clonal expansion of T cells
What can be found on the surface of cytotoxic T cells? TCRab receptor CD8 receptor
All cells with a nucleus have... MHC Class I molecule when this is attached to a viral protein this becomes activated this interacts with CD8 receptor followed by death by apoptosis
Wasps and bees - what has this got to do with killer Ts? CD8 T cells can kill repeatedly like wasps sting repeatedly without dying whereas neutrophils die in the process of killing the invading pathogen - like a bee dies after it stings you
Explain how apoptosis works nuclear blebbing - detachment of cortex from the plasma membrane alteration in cell morphology cell membrane remains intact shedding of small membrane vesicles DNA is fragmented by controlled digestion by nuclease enzymes apoptopic bodies are removed by phagocytic cells
How do cytotoxic cells induce apoptosis? armed cytotoxic T cells have lytic granules (modified lysosomes) which contain: perforin - this modifies the target cell by forming pores in the cell membrane granzymes - these proteases start chopping up proteins in the target cell granulycin is also another protein
What is the method of killing for perforin and granzymes? the former forms pores in the cell membrane the latter binds to proteins in the cell membrane
How are CD8 T cells and NK cells similar? they both secrete granzymes
CD8 T cells release harmful granzymes. Why are they themselves not affected? because they have inhibitors of granzymes these are serine protease inhibitors
Give an overview of how CD8 T cells kill infected cells clonal expansion of CD8 in lymph nodes activated CD8 leaves LN and goes to site of infection start to bind cells with MHC attached to peptide on its surface (target cells) kills them
CD8 T cells kill in a specific and directional way. Explain how they do this CD8 grabs target cell in non-specific way TCR:MHC:peptide interaction smack forms reorganisation of microtubule organising centre and Golgi apparatus lytic granule release
Which immune system are NK cells considered a part of? innate immune system
What are two similarties and two differences between CD8 T cells and NK cells similarities -both lymphocytes -both kill using granzymes differences -NK cells are a bit bigger -NK cells have no antigen-specific receptors
How do activated NK cells avoid killing normal cells? missing-self hypothesis recognition of 'self' = no killing by NKcells recognition of 'missing self' = killing by NK cells (if response is 'not self' or response is missing)
Viruses 'hide' inside normal cells- how are these infected cells killed? viruses down-regulate MHC class I to avoid CD8 T cell but because MHC Class I on surface is gone nothing to respond to NK cells killing by NK cells
What type of cells do NK cells and CD8 T cells kill? infected cells and tumour cells
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