Flashcards
Week 2 (Dr Ireland)
Cards in this deck (37)
- 1What types of pathogens are extracellular and what type of pathogens are intracellular?Extracellular: bacteria, some viruses, fungi, parasites
Intracellular: viruses, some bacteria - 2How do commensal microorganisms contribute to the immune system?
- 3What is the complement system?A system of plasma proteins that mark pathogens (via opsonisation) for destruction.
- 4What are the three pathways of the complement system and what do they do?
- 5Which complement pathway acts first?The alternative pathway.
- 6Why is the cleavage of C3 into C3b and C3a so significant?Because C3b tags the microbe for phagocytosis (this is called complement fixation) and C3a recruits the phagocytes.
- 7How does the alternative pathway make a soluble C3 convertase and what is it called?The soluble C3 convertase (iC3Bb) starts off the alternative pathway.
- 8How does the alternative pathway make a fixed C3 convertase and what is it called?The pathogen-bound C3b also binds fator B to facilitate the cleavage of factor B by factor D. This results in C3bBb - the next, more potent C3 convertase.
- 9Which regulatory plasma protein allows C3bBb to extend its lifespan on microbial surfaces?Properdin (factor P) prevents C3bBb degradation by binding to it and allowing it to continue its convertase function.
- 10What happens when we have enough C3b for opsonisation? How do we stop more convertases from being formed?Factor H binds to C3b making it susceptible for cleavage by factor I. The product of this cleavage is iC3b which remains attached to the pathogen but can't form convertase.
- 11How do we stop human cells from being opsonised by C3b as well?Human cells have membrane proteins (DAF and MCP) that rapidly disrupt the action of C3bBb convertase if it is deposited on the human cell.
- 12What is the goal of opsonisation?To attract a macrophage for phagocytosis. The macrophages indentify the C3b coating because they express complement receptor 1, or CR1.
- 13Phagocytosis is the first line of defence. Aside from phagocytosis, what is something else the complement system is capable of?Creating membrane pores in microbes and lysing them. This is achieves by a group of complement proteins that form the membrane-attack complex.
- 14What is the critical first step of this process?The cleavage of C5 into C5a and C5b (by a different convertase - C3b2Bb - that we don't need to know about). C5b intitates the formation of the membrane-attack complex.
- 15How does the membrane attack complex work from there?
- 16Which complement fragments are anaphylatoxins? (and what is an anaphylatoxin)C3a and C5a are anaphylatoxins. They induce inflammation and in certain situations they can cause anaphylactic shock.
- 17Which classes of plasma protein limit the spread of infection and how?1. Formation of blood clots in the efflux areas via coagulation proteins.
2. the Kinin system induces vasodilation in the influx areas to allow immune mediators to reach the site of infection at a faster rate.
3. Protease inhibitors (inhibit the defensive proteases that are secreted by pathogens) - 18What are antimicrobial peptides?Antimicrobial peptides (e.g. defensins) kill pathogens by perturbing their membranes.
- 19What are pentraxins?Plasma proteins of the innate immune system that bind microorganisms and target them to phagocytes
- 20What are the two principle types of reactions of the innate immune system?Inflammation and antiviral defence
- 21What two molecular patterns to innate immune receptors recognise?PAMPs (pathogen-associated molecular patterns) and DAMPs (damage-associated molecular patterns)
- 22Are the pattern recognition receptors of the innate immune system clonally distributed?No. They are non-clonally distributed (i.e. they are identical on all cells of a particular type).
- 23What do toll-like receptors look like?A hook
- 24Where are TLRs found?On the cell surface and in endosomes of innate immune cells.
- 25What do TLRs recognise?Cell surface: microbial proteins, lipids and polysaccharides
Endosomes: microbial nucleic acid - 26What signals do TLRs generate upon activation?Signals that activate TFs to transcribe genes encoding cytokines, enzymes, and other proteins involved in the antimicrobial functions of activated phagocytes and other cells.
- 27What are NOD-like receptors (NLRs) and what do they do?NLRs are cytosolic receptors that recognise PAMPs and DAMPs in the cytosol.
- 28What is the inflammasome?The inflammasome is a complex created when NOD-like receptors P-3 (NLRP-3) is stimulated and forms a complex with an adaptor protein and caspase-1. Together they generate IL-1beta.
- 29What are RIG-like receptors?RLRs recognise RNA produced by viruses in the cytosol and they react by activating signalling pathways that result in the production of type 1 interferon (IFN).
- 30Where do macrophages come from?Macrophages are either derived from progenitors (resident macrophages in the brain etc.) or from monocytes circulating in the blood.
- 31Which cytokine is involved in classical macrophage activation?IFN-gamma
- 32Which cytokines are involved in alternative macrophage activation?IL-4 and IL-13
- 33What are the two main functions of dendritic cells?To initiate inflammation and stimulate adaptive immune responses.
- 34What function do mast cells serve in the innate immune system?Mast cells are bone marrow-derived cells with abundant cytoplasmic granules that are present in the skin and mucosal epithelium. They can be activated by TLRs or antibodies. They contain proteolytic enzymes and vasoactive amines such as histamine that cause vasodilation. They stimulate inflammation and also provide defence against helminths and allergic reaction.
- 35What do natural killer (NK) cells do?They recognise infected/stressed cells and respond by killing the cell and secreting IFN-gamma to activate macrophages to clear the debris. They induce apoptosis in the infected cell by vomiting the contents of their granules into it.
- 36Name 3 NK cell activating cytokines.IL-15, IL-12 and type 1 IFNs
- 37What is inflammation?Inflammation is a tissue reaction that delivers mediators of host defence - circulating cells and proteins - to sites of infection and tissue damage.
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- IMED2001 (Immunology: Innate Immunity) Flashcards on Week 2 (Dr Ireland), created by Allira Payne on 04/06/2018.
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