Flashcards
How does the immune system kill pathogens which live inside cells
Cards in this deck (35)
- 1What are the components of the cell-mediated immune response? (3)1) Cytotoxic T cells
2) NK cells
3) T cell-dependent macrophage activation - 2Give six examples of disease which are all caused by intracellular bacteria1) Respiratory
2) Legionnaire's Disease
3) Listeriosis
4) Meningitis
5) Typhoid fever
6) TB - 3What does chlamydia pneumoniae cause?Respiratory infections
- 4Why did legionnaire's disease used to be common?Often outbreaks in old people's homes, a bird or something similar would infect the the water supply
- 5How are infected cells killed? (3)CD8 T cells
NK cells
Macrophages - 6Which cell is the most effective killer of infected cells?CD8 T cells.
- 7What happens in a chronic infection if CD8 T cells fail to eliminate it?CD8 T cells will be switched off - for example in individual with HIV, prior to treatment availability, they would have no CD8 response at all after a while. Thought to be protective as CD8 T cells can cause damage to surrounding tissue.
- 8How does sensitisation work? Where is it performed?1) Very small amount of pure form of protein is injected in repeated doses to switch of the T cell response.
2) In hospital in case the individual crashes - 9What dampens down the immune response in the absence of a pathogen?Dendritic cells present self protein to Th17 cells, which induces peripheral tolerance and dampens down the immune response.
- 10How are vaccinations delivered?In Complete Freud's adjuvant - contains dead pathogens. Induces immune response and memory cell production.
- 11What is thought to trigger some autoimmune diseases? Give an example?1) Infections
2) Epstein virus and MS - 12What do CD8 T cells express?TCRaB and a CD8 co-receptor
- 13How long is the MHC class I receptor?~10 amino acids long
- 14What is the difference in how T cells recognise antigens vs how antibodies recognise antigens?Antibodies can recognise freely floating antigens, T cells can't.
- 15Which MHC class do CD8 T cells recognise?MHC class I - expressed on all cells
- 16What three types of cells do CD8 T cells kill?1) Virally infected cells
2) Mycobacteria infected cells
3) Tumour cells - 17How do CD8 cells kill cells?Induce apoptosis in the target cell - this prevents the pathogen from re-entering the environement
- 18What causes the yellowish-green colour of pus?Elastase released from dead neutrophils
- 19What are the steps in apoptosis? (6)1) Nuclear 'blebbing'
2) Changes in cell morphology
3) Membrane remains intact
4) Formation of small membrane vesicles
5) DNA is fragmented by controlled digestion by nuclease enzymes
6) Apoptotic bodies are removed by phagocytic cells - 20What do T cells contain?Lytic granules (modified lysosomes) - modified lysosomes
- 21What is contained within the lytic granules? (2)1) Perforin
2) Granzymes - 22What is the function of perforin?Punches holes/pores in the target cell membrane
- 23What is the role of granzymes?Proteases which cleave proteins in the target cell to initiate apoptosis
- 24What are the two theories regarding how granzymes enter the target cell?1) Ions enter through pore, destabilising the electric gradient of the pore. Transporters reverse (flip/flop-ases). Granzymes enter by attaching to reversing proteins
2) Pore expands to allow entry of the granzymes - 25How are the cytotoxic effector molecules of T cells secreted in a focused manner?LFA-1 (expressed on T cell) binds to ICAM-1 on target cell. Two sets of the interaction, forms a seal in between them. This is a non-specific adhesion. If the TCR:MHC:peptide interaction is successful the cytotoxic effectors are then released.
- 26What happens just before the cytotoxic content of the CD8 cells is released?Lytic granules line up at front end of cell (toward target), GA and microtubule organising centre are reorganised.
- 27What are NK cells part of?The innate immune system
- 28What class of cells do NK cells belong to? What do they lack?1) Lymphocytes
2) Antigen-specific receptors - 29How do NK cells kill?Same as cytotoxic T cells - use perforin and granzymes
- 30How NK cells activated? What do activated NK cells secrete? How much more effectively do activated NK cells kill target cells?1) Via cytokines
2) Secrete IFN-y
3) 20-100X more efficient - 31How do NK cells kill infected cells and avoid killing normal cells?Missing-self hypothesis: recognition of self = no killing; recognition of 'missing-self' = killing by NK cells
- 32What is and what mediates hyperacute rejection? What causes women to be unable to carry to full term?1) Rejection on the operating table
2) NK cells
3) Overactive NK cells - a large portion of IVF is often to do with getting rid of NK cells - 33How do NK cells recognise self peptides? Where are these receptors located?1) MHC class I receptors are too unstable to have nothing in them, will express a self peptide in an absence of a pathogen. NK cells have learnt to recognise its own MHC/HLA while developing in the bone marrow. Self-peptide in MHC class I stimulates the inhibitory receptor.
2) The inhibitory and activating receptors on NK cells interact with the side of the MHC class I. - 34How do NK cells recognise the absence of self?Many viruses stop the MHC from reaching the surface and cause the cell to express stress signals. Stress signals stimulate the activating receptors on NK cells
- 35How do NK cells recognise cancer cells?Cancerous cells grow so quickly that they often lack MHC class I