Complement System Flashcards
Enzymes of proteinase which are heat-labile series of 18 plasma proteins
COMPLEMENT SYSTEM (C’)
True or False. Complement system are NON-SPECIFIC proteins, therefore, part of Innate Immunity
True
small letter after the number indicates that the protein is a smaller protein resulting from the cleavage of a larger precursor by a protease
Fragments
True or False. “a” is denoted as bigger fragments
False. ‘a’ means “ang gaan”, therefore smaller fragment
True or False. “b” is denoted as smaller fragments
False. ‘b’ means”BIGAT”, therefore Bigger fragment
Fixation/Inactivation of C’ proteins
56 C for 30 mins
61 C for 10 mins
Converging point of all three pathways
C3-C3b
Major function of C” proteins
Lysis of foreign cells and immune complexes
Effects of C”
Lysis Opsonization Facilitate B-cell activation Mediators Increase vascular permeability
Three Complement Pathways
Classical Pathway
Alternative Pathway
Mannose Binding Lectin Pathway
Three major stages of Complement Pathways
- Recognition unit
- Activation unit
- Membrane Attack Complex
Activators of Classical complement Pathway
Immune Complexes (IgG, IgM)
Apoptotic Cells
C reactive protein bound to ligand
C1 complex (calcium dependent) are composed of three subunits:
C1q, C1r, C1s
Functions:
C1q
C1r
C1s
C1q: Binds to FC region of IgM and IgG
C1r: Activates C1s
C1s: Cleaves C4 and C2
True or False. Activation of Classical Pathway needs two molecules of IgM, and one molecule of IgG
False:
IgG - two molecules
IgM - one molecule
C3 convertase of Classical pathway of Classical Pathway
C4b2a
Major constituent of the complement system
C3
C5 convertase
C4b2a3b
A unique system that builds up a lipophilic complex in cell membranes from several plasma proteins
Membrane Attack Complex
Complex that polymerizes C9 to form a tubule (pore)
C5bC6C7C8 complex
How does C9 lyse cell?
It disturbs the lipid bilayer to allow the free exchange of ions and water molecules across the membrane influx of sodium, and (Na+) ions and H2O leads to disruption of osmotic balance
Alternative Pathways is also known as?
PROPERDIN PATHWAY
First protein to function in the alternative pathway
Properdin
Function of Properdin
Stabilizes the pathway and increases half life of C3bBb
Analogous to C2 in the classical pathway
Factor B
Activators of Alternative Pathway
Inulin
Zymosan
Bacterial polysaccharides and endotoxins
AGGREGATES of IgA
Major inihibitory regulator of Alternativ e pathway that blocks the formation of C3bBb
Factor H
Plasma protein that activates Factor B
Factor D
C3 convertase of Alternative Pathway
C3bBb
C5 convertase of Alternative Pathway
C3bBb3b
True or False. Alternative Pathway is activated by the PRESENCE of specific antigen-antibody complexes
False. Activation of AP is by the ABSENCE of specific antigen-antibody complexes
Plays an important role as a DEFENSE MACHANISM OF INFANCY
Mannose Binding Lectin Pathways
Proteins that bind to carbohydrate and is homologous in structure to C1q
Lectins
MASP
Mannose-binding lectin–associated serine protease
Two serine protease that interact and activates complement system.
MASP1 (minor)
MASP2 (major)
Takes the active role in cleaving C4 and C2
MASP2
Functions: C5 -C9
MAC
It functions for opsonization
C3b - iC3b
Functions for PMNs activation
C5a
Function: C5a>C3a>C4a
Chemotaxis & Anaphylatoxins
Hypocomplementemia
Result from the complexing of IgG or IgM antibodies capable of activating complement
True or False. • Chronic activation of complement levels are elevated in many inflammatory conditions.
True
Causes of decreased complement levels
- Complement has been excessively activated recently.
- Complement is currently being consumed.
- A single complement component is absent because of a genetic defect
- Coexists with SLE and other disorders associated with an immunopathologic process
Deficiency of C1qrs complex is associated to:
SLE-like syndrome
Deficiency: C5 - C8
Neisseria infections
Deficiency: C1 INH
Hereditary angioedema
Most common complement deficiency associated with recurrent pyogenic infections
C2
Deficiency: PROPERDIN
Neisseria infections
Stimulus: Classical Pathway
Immune Complexes (IgG and IgM)
Stimulus: Alternative Pathways
Endotoxins, LPS
Stimulus: Mannose Binding Lectin Pathway
Terminal MANNOSE group
Key intermediate in all pathways
C3
Recognition Unit of Classical pathway
C!qrs comples
C1qrs complex is ________ dependent
Calcium dependent
Antibody structure that binds to complement
Fc region
Cleaves C4 and C2
C1s
Binds to Fc region of IgG and IgM
C1q
Activates C1s
C1r
Stabilizes C3 convertase in alternative pathway
Properdin
Analogous to C2
Factor B
Factor B
Binds to C3 to form C3 convertase
Factor D
Activates and Cleaves Factor B
Major Regulator of Alternative pathway
Factor H
Recognition unit in MBL Pathway
MBL
MBL is homologous to _______ complex
C1qrs complex
In MBL, it cleaves C4 and C2
MASP-2
Major MASP in MBL
MASP-2
MASP-2 is homologous to ____ in classical pathway
C1s
MBL is produced in the _____
Liver
Plasma Complement Regulators
Factor I: Factor H: C1 inhibitor: C4-binding protein: S-protein:
Plasma Complement Regulators
Factor I: Cleaves C3b and C4b
Factor H: inactivate C3b and prevents binding of B to C3b
C1 inhibitor: Dissociates C1r and C1s, from C1q
C4-binding protein: Inactivate C4b
S-protein: Prevents attachments of the C5b67 complex in cell membrane
Dissociates C1r and C1s, from C1q
C1 inhibitor
Inactivate C3b and prevents binding of B to C3b
Factor H
Cleaves C3b and C4b
Factor I
Prevents attachments of the C5b67 complex in cell membrane
S-protein/vitronectin
Most common complement deficiency
C2
Most severe type of complement deficiency
C3
What complement deficiency manifests Neisseria infections
C5-C8
Properdin
Complement deficiency in Hereditary angioedema
C1 INH
C1s complement deficiency result to:
SLE
Factor H and Factor I deficiency
Recurrent Pyogenic infections
Deficiency complement in PNH
DAF
MIRL
Deficiency in MASP-2 causes _____________
Pneumococcal infections