Complement System Flashcards
Complement proteins
plasma proteins produced mainly in the liver, complement action of antibodies in destruction of bacteria, ridding the body of foreign substances (antigens) etc
Classical pathway
Antibodies (igG or IgM) are recognized by complement proteins (C1 complex)
When the C1 complex interacts with antibodies what part of the complex recognizes the antibody, activating what complement proteins that have what substrates
C1Q, activates C1r cleaving C1s and converting it to an enzyme whose substrates are C2 and C4
When C4 protein is cut what product interacts with the antigen surface, what does it complex with
C4b, C2a creating the C4BC2a complex
C4BC2a complex is also known as what enzyme, what is its function
C3 convertase, catalyzes the protelytic cleavage of C3 and holds C3b
When C4bC2a/C3b is formed what is the substrate it interacts with, what stays bound
C5, C5b
T/F: When C5b stays bound it stays on the C4bC2a/C3b complex
False: C5b stays bound to the pathogen
What proteins does C5b recruit, which one opens a pore in the antigen
C6,C7,C8,C9/C9
What does the pore created in the antigen cause
H20 and ions enter the pathogen causing the cell to swell and lyse
lectin
cell surface protein that recognizes and bids sugars or oligosacchardies
In the lectin pathway what recognizes pathogens
Mannose binding lectin (MBL)
T/F: Mannose residues are typically not found on self proteins allows MBL to float freely
True
Ficolins
plasma proteins that coat different species of bacteria causing complement proteins to attack (opsonization), recognizes NAG
What does MBL typically complex with
Mannose Associated Serine Porteases (MASP), MASP-2 cleaves c4 and c2 forming C4bC2a complex
When does the lectin pathway become analogous to the classical pathway
Once the C4aC2b complex is formed leading to cleavage of C3 and C5
What occurs in initiation of the alternative pathway
circulating C3 slowly cleaves itself and binds to a pathogen, factor B binds to C3B and is cleaved to Bb
C3b and Bb come together to create what enzyme, what is the result of this
C3 convertase, many C3bs cover a pathogen eventaully causing a C5 to be cleaved and C5b to be bound
T/F: The classical, leptin, and alternative pathways all converge on C5b is bound
True
In regulation of the classical pathway what protein prevents complement activation
C1 esterase inhibitor (C1INH)
In regulation of the classical pathway which proteins cause dissociation of C4b2a
C4 binding protien (C4BP), DAF, CR1/CD35, MCP
In regulation of the classical pathway which protein cleaves C4b after C2a leaves
Factor I
In regulation of the alternative pathway which protein binds to C3bBb complex and displaces Bb
Factor H
As a major function of complement which protein causes opsonization
C3b
As a major function of complement which proteins cause anaphylatoxin production
C5a,C3a,C4a
As a major function of complement which proteins cause cell lysis
C5b-C9
What are other minor activities of complement
enhancement of B-Cell receptors, removal of immune complexes, removal of necrotic cells and subcellualr membranes
