Complement Flashcards
What three things can the complement cascade be activated by?
Antibody complexes, foreign surfaces, and mannose residues.
What is C4b2b in the classical pathway?
A C3 convertase which cleaves C3 to C3a and C3b (binds to th microbial surface or convertase).
What triggers the lector pathway of complement activation?
Mannan-binding lectin deposition on mannose residues with specific spatial arrangement.
What happens when C3 is cleaved to make it reactive?
A reactive thio-ester at Cys998 is exposed is exposed which reacts with hydroxyl groups (takes precedence over amino acid groups due to the close proximity of a His residue).
In the alternative pathway, what is a transient C3 convertase?
C3(H2O)Bb
What causes the alternative pathway to be activated?
When the rate of C3 conversion rises above the rate of convertase deactivation.
Name two regulators of the alternative pathway.
Decay accelerating factor (DAF)
P pathogen factor
When opsonins bind to complement receptors on effector cells, what happens?
Cross-linked of the receptors via deposited opsonins.
In formation of the membrane attack complex, what is a main role of C7C8C9?
Exposes hydrophobic sites which increase the affinity for lipid bilayers.
In inflammation, what are C3a and C5a inactivated by?
Carboxypeptidase
Three ways in which Ebola evades the immune system.
IFN production decreased, prevention of dendritic cell maturation, increased apoptosis of NK cells and T cell via Fas/Fas-L cascade.
What is the folding pattern of immunoglobulin domains called?
The immunoglobulin fold.
Where are the hypervariable regions and how many amino acids are they each?
In the variable region domains at the Nter loops, they are ~7-12 amino acids each.
How many B strands do the immunoglobulin folds in the C and V domain have respectively?
7 and 9.
Why are soluble antibodies unusual?
Most members of the Immunoglobulin supergene family are surface receptors.
