Flashcards
Complement System
Cards in this deck (67)
- 1Define complementA series of plasma proteins which, when activated, interact sequentially to form a self-assembling enzymatic cascade generating biologically active molecules which mediate a range of end processes.
- 2Approximately how many plasma proteins form the complement system?Approximately 30
- 3What is an enzymatic cascade?Pro-enzyme converted to enzyme
This enzyme activates another pro-enzyme
Creates an amplification effect - 4How are enzymatic cascades controlled?Regulatory factors act at specific points in the cascade
- 5What are the 3 different initiation pathways in the complement system?Classical
Lectin
Alternative - 6What is the end point molecule of all 3 initiation pathways?C3b
- 7Which pathway is activated by the end point molecule of the initiation pathways?Terminal pathway
- 8Give 4 end effects of the terminal pathwayCell lysis
Inflammation
Opsonisation
Interact with other pathways - 9What activates the classical pathway of the complement system?Antigens that trigger complement molecules, for example on the cell membrane of a pathogen
- 10What is the function of complement molecules?Damage membranes of cells which they bind to
- 11What is the first step of the classical pathway?Antibody binds to antigen epitope
- 12What is the second step of the classical pathway?C1 protein binds to antibody
- 13What is the structure of the C1 protein?3 subunits C1q, C1r and C1s
All subunits act as enzyme - 14How does the C1q subunit attach to the antibody?Through CH2 domain
- 15WActivation of C1 subunits q then r then s
- 16What is the fourth step in the classical pathway?Activated C1s subunit acts on the complement molecule C4, activating it by splitting into C4a and C4b subunits
- 17What is the fifth step in the classical pathway?C4b subunit binds to antigen (but not C4a)
- 18What is the sixth step in the classical pathway?C2 complement protein associates with C4b subunit
- 19What is the seventh step in the classical pathway?C1s acts on C2 complement protein, activating it by splitting into C2a and C2b subunit
- 20What is the eighth step in the classical pathway?C2b subunit remains bound to C4b subunit (but not C2a)
- 21What is the name for the C4b + C2b complex?C3 convertase
- 22What is the ninth step in the classical pathway?C3 convertase activates C3 by splitting into C3a and C3b subunit
- 23What is the tenth step in the classical pathway?C3b subunit forms a complex with C2b and C4b
- 24What is the name for the C4b + C2b + C3b complex?C5 convertase
- 25What is different about the lectin pathway in comparison with the classical pathway?Mannan binding lectin directly activates C4 and C2 to form C3 convertase, independent of antibody and C1
- 26Why is the control of complement molecules important?Can be toxic
- 27Give a regulatory mechanism of complement molecules that does not involve enzymesShort half life of complement molecules
Spontaneously degrade after a short time - 28Give a regulatory mechanism of the C1 complement moleculeC1 inhibitor dissociates the r and s subunits
- 29Give 2 regulatory mechanisms of the C3 convertase complexC4 binding protein displaces C2b
Factor I converts C4b into the inactive fragments C4c/d - 30Give a regulatory mechanism of the C5 convertase complexFactor I converts C3b into inactive C3c/d fragments
- 31What is the function of membrane regulatory proteins?Prevent complement pathways being activated on the surface of normal cells
- 32How do regulatory proteins work?Disrupt C3 convertase formation
- 33Give 3 examples of membrane regulatory proteins in the complement systemDAF
CR1
MCP - 34What is meant by the 'tick over' phase of the alternative pathway?Continually active at low levels in normal individuals
- 35Where does the 'tick over' phase of the alternative pathway occur?Extracellular fluid
- 36Where does the active phase of the alternative pathway occur?Surfaces of cells in the presence of trigger factors
- 37What is the main difference between the alternative pathway and the classical pathway?Alternative pathway does not require antibodies
- 38What is the first step in the 'tick over' phase of the alternative pathway?C3 undergoes spontaneous proteolysis to form C3i
- 39What is the second step in the 'tick over' phase of the alternative pathway?Factor B interacts with C3i to form a complex
- 40What is the third step in the 'tick over' phase of the alternative pathway?Factor D targets Factor D and activates it by splitting into Ba and Bb subunit
- 41What is the fourth step in the 'tick over' phase of the alternative pathway?Bb subunit remains bound with C3i
- 42What is the name for the Bb + C3i complex?C3 convertase
- 43What is the fifth step in the 'tick over' phase of the alternative pathway?C3 convertase activates C3 by splitting into C3b and C3a subunit
- 44What is the final step in the 'tick over' phase of the alternative pathway?Factors H and I break down C3b into inactive C3c/d fragments and the pathway ends
- 45What is the function of the 3 membrane regulatory proteins in the 'tick over' phase of the alternative pathway?Inactivates any C3b landing on the cell
- 46What initiates the active phase of the alternative pathway?C3b from 'tick over' phase can bind to trigger surface
- 47What is the second step in the active phase of the alternative pathway?Factor D activates Factor B on cell surface, forming Bb (remains bound to C3b) and Ba
- 48What is the third step in the active phase of the alternative pathway?Properdin stabilises C3b and Ba complex, forming C3 convertase
- 49What is meant by the amplification loop of the alternative pathway?C3 convertase activates more C3 into C3a and C3b
- 50What is the final step in the active phase of the alternative pathway?Additional C3b molecule added to C3 convertase, forming C5 convertase
- 51What is the initial molecule in the terminal pathway?C5 convertase from classical/alternative/lectin pathway
- 52What is the first step in the terminal pathway?C5 convertase activates C5 by splitting into C5a and C5b subunit
- 53What is the second step in the terminal pathway?C5b combines with C6, C7, C8 and multiple C9 molecules forming a Membrane Attack Complex
- 54What does the abbreviation MAC stand for?Membrane attack complex
- 55Give 2 effects of the C5a subunitChemotactic
Anaphylactic - 56What is the function of the C59 molecule?Membrane Attack Complex inhibitor
Breaks down Membrane Attack Complex if not required as it can be toxic - 57What is meant by cytolysis?Cell breakdown
- 58How do complement molecules cause cell lysis?Membrane Attack Complex inserts through lipid bilayer of cells, forming pores
Creates osmotic imbalance so sodium and chloride ions pass into cell
Water drawn into cell by osmosis
Osmotic lysis - 59Which cells are more likely to be affected by osmotic lysis?Occurs in bacteria more than viruses
Lysis of cells also occurs in Type II hypersensitivity - 60What is the function of C3a, C2a and C5a?Generate biologically active molecules for inflammatory process
Especially C3a and C5a - 61How do C3a and C5a affect the action of immune cells?Form chemotactic gradient for immune cells, as these subunits are generated at the site of bacteria
Degranulation of mast cells, which contributes to inflammation - 62What is the effect of C3a and C5a on muscle?Smooth muscle contraction (especially in airways)
- 63What is the effect of C3a and C5a on capillaries?Vasodilation - increases space between endothelial cells
Causes oedema which dilutes bacterial toxins
Immune cell extravasation
Local influx antibody and complement - 64What is meant by phagocytosis by non-specific adherence?Antibodies can agglutinate particulate antigens to form a larger target for macrophages
- 65How can complement molecules aid opsonisation?Antigen can be coated with antibody - recognised by macrophage Fc receptor
C3b can also opsonise antigen - also recognised by C3b macrophage receptor - 66What is the function of macrophages in the liver and spleen?Remove antigens from the blood
- 67What is meant by immune adherence?Erythrocytes have C3b receptors so can transport antigen (which has been opsonised by C3b complement) to macrophages in the liver and spleen
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- Animal Disease 1 (Immunology) Flashcards on Complement System, created by Florence Edwards on 06/10/2016.
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