Innate immunity Flashcards
What physical barriers are present to prevent microbe entry? [2 marks]
- Skin (slightly acidic)
- Mucosal surfaces trap pathogens and have enzymes to kill them
What chemical barriers are present to prevent microbe entry? [2 marks]
- Low pH of the stomach
- Lysosomes in tear ducts to punch holes into the plasma membrane
What cells are phagocytic? [3 marks]
- Monocytes/Macrophages
- Granulocytes (e.g. eosinophil, basophil)
- Neutrophil
What does the inflammatory response do (in terms of blood vessels and immunity)? [4 marks]
- Recruits neutrophil via enhanced permeability and discharge
- Closes off the site of infection via cell adhesion and clotting
- Releases pro-inflammatory cytokines and chemokines
What do cytokines do? [2 marks]
- Act to modify the behaviour of cells in the immune response
- For example, make T cells work more effectively
What do chemokines do? [2 marks]
- Act as chemotactic factors
- They create concentration gradients from the site of infection which attract (or repel) specific cell types
Which cell types produce IL-1? [2 marks]
- Macrophages
- Keratinocytes
What does IL-1 do to the liver? [2 marks]
- Causes it to make a lot of complementary proteins
- Upregulates clotting factors
What does IL-8 do? [1 mark]
Acts as a chemoattractant for neutrophils
What does IL-12 do to naïve T cells?
- Diverts immune response to type 1 (cytotoxic)
- Proinflammatory response
- Cytokine secretion
What does TNF-α do to blood vessels? [2 marks]
- Produces cell-adhesion molecules (i.e. E- and P- selectins)
- Makes blood vessel walls more permeable
How do macrophages recognise microbes? [3 marks]
- Have phagocytic receptors that bind microbes and their components
- Receptors include complement and scavenger receptors
What are some examples of pattern associated molecular patterns (PAMPs)? [5 marks]
- Gram positive and gram negative bacteria
- Bacterial flagellin
- Abnormal protein glycosylation
- Abnormal nucleic acids
What do gram negative bacteria have? [2 marks]
- Lipopolysaccharides on the outer membrane
- These are lipids that anchor with the polysaccharide chain
What do gram positive bacteria have? [4 marks]
- Small peptide chains on the outer membrane
- Teichoic acid
- Lipoteichoic acid
- Peptidoglycan
What are pattern recognition receptors (PRRs)? [2 marks]
- Host factors that recognise a specific type of PAMP
- There are 3 classes of PRR; secreted, extra- and intercellular (cytoplasmic)
Where are PRRs encoded? [1 mark]
In the germ line
What do extracellular PRRs do? [2 marks]
- Recognise PAMPs outside of a cell
- Trigger a co-ordinated response to the pathogen
What do intracellular (cytoplasmic) PRRs do? [2 marks]
- Recognise PAMPs inside a cell
- Act to co-ordinate a response to the pathogen
What do secreted PRRs do? [1 mark]
Tag circulating pathogens for elimination
What does the interferon system deal with? [1 mark]
Viral infections
How does the interferon system deal with infected cells? [2 marks]
- Uses cytoplasmic PRRs (RIG-like receptors) that detect viral RNA
- Prevents the infected cell from replicating by shutting down metabolism and replication
How do interferons prevent autoimmunity? [2 marks]
- Binds to interferon receptors on self cells
- Only mounts a response if the cell doesn’t have receptors.
Where are complement proteins made? [1 mark]
In the liver
What do complement proteins do? [2 marks]
- Recognise PAMPs on the surface of microbes
- Tag them
How are microbes cleared after being tagged by complement proteins? [3 marks]
- Phagocytosed
- Opsonised (coated to prevent entry into cells)
- Holes are punched into them
What are the three ways of activating complement proteins? [3 marks]
CLASSICAL PATHWAY: recognition of LPS and other PAMPs by C1q components
LECTIN PATHWAY: non-host glycosylation recognised by MBP and other lectins
ALTERNATIVE PATHWAY: Membranes that do have proteins to shut down complement are recognised as non-self
Structure of Natural Killer (NK) cells [3 mark]
- Lymphocyte-like
- Large
- Granular cytoplasm
What do NK cells do? [2 marks]
- Kill certain tumours & virally infected cells
- Inject granzymes and perforins
What do NK cells recognise? [2 marks]
- MHC molecules (or lack there of)
- Activating ligands
What are some defects of complement proteins? [2 marks]
CORE: cause autoimmune diseases (e.g. lupus)
NON-CORE: linked to susceptibility to pathogens like Neisseria
What are some macrophage deficiencies? [2 marks]
- Chronic granulomatous disease: no oxidative burst
- IRF8 mutations: links to susceptibility to TB
What are some defects of cytokines? [2 marks]
- Aicardi–Goutières syndrome: constant inflammation
- Lack of interfern-responsiveness: sensitivity to viral infections
