9 B Cell Mediated Immunity II: Complement Cascade Flashcards
Where are complement proteins made?
Liver
What is the main goal of complement?
Permanent tagging
What three pathways does the complement system have?
Lectin
Alternative
Classical
What is the Lectin pathway?
MBP
MASP 1 and 2
C4 and C2 cleavage to C3 convertase
same as classical and alternative from here
What is the Alternative pathway?
C1 binds the Fc region of an antibody
C1qrs is cleaved, rs activates C4 and C2
C3 convertase is formed
C3b binds to surface to opsonize
What is the Classical pathway?
Basically a positive feedback system
C3b binds
Factor B
Factor D
C3Bb forms to make alternative C3 convertase
other C3bs are created, and C3Bb3b forms to increase positive feedback loop
What phagocyte receptor recognizes the C3b on the surface of a pathogen?
CR1 of phagocytes
What is CR2 and why is it clinically important?
Epstein Barr Virus infected cells use this coreceptor as a gateway to the B cell
What opsonizing proteins are recognized by CR2?
C3d
C3dg
iC3b
Epstein Barr virus
What is a CR2 receptor and where is it located?
Synergistic Coreceptor for B cells, FDCs
What complement receptors can act on their own to initiate phagocytosis? By binding what?
CR3
CR4
by binding iC3b
How are complement reactive complexes mainly eliminated?
Via the RBC CR1 receptor binding to C3b or C4b, taking this to the splenic macrophages for engulfment.
If a complement complex gets to the kidney, what removes them from the glomerulus?
Podocytes
What disease is caused by a overflow of complement complexes due to autoimmune reactions?
Systemic Lupus Erythmatosis (SLE)
this can cause kidney failure and chronic inflammation
What proteins form the Membrane Attack Complex?
C5b, 6,7,8,9
What is the classical C5 Convertase?
C4b,C2a, 3b
What is the alternative C5 convertase?
C3b2, Bb
What does a lack of the MAC leave us vulnerable to?
Neisseria Species infections
What does a lack of C5a lead to?
Lessened Neutrophil chemotaxis,
Leiner disease in infants
What are the main chemoattractants?
C3a
C4a
C5a
(the parts of the complement that do not get used in C3 or C5 convertase)
What is the most powerful chemotractant?
C5a
What does C5a induce?
Neutrophil and Macrophage chemotaxis
C1 and C3 production in liver
What two main locations do complement regulatory proteins reside?
Plasma
Cell Surface
What are the plasma regulator proteins?
C1 Inhibitor (C1INH)
C4 Binding Protein (C4BP)
Factor H
Factor I
What are the cell surface complement regulatory proteins?
Decay Accelerating Factor (DAF)
Membrane Co-factor Protein (MCP)
Complement Receptor 1 (CR1)
CD59
What complement protein do almost all regulatory proteins attach to?
C3b and C4b
these are the most crucial hubs
What complement proteins do the non-c3b or c4b binding regulatory binding proteins bind to?
The complement protein in their name!
C1INH, C4BP, CD59
What is the regulatory protein for the MAC?
CD59
binds to C5b,6,7,8 complex for factor I
What complement regulatory proteins bind complement for factor I action?
C4BP
Factor H
MCP
CR1
What disease is due to a defect in CD59 or DAG?
Paroxymal Nocturnal Hemoglobinuria
What disease is due to a defect in C1INH?
Heriditary Angioneurotic Edema (HANE)
pts have big lips and swollen faces
What chemotractants bring in mast cells?
C3a
C5a
What complement pathway is reliant on B cells to work?
Classical
What antibody pathway is the first to work?
Alternative and Lectin
What were the diseases we discussed from the complement system?
Lupus HANE Paroxymal nocturnal hemoglobinuria Neisseria infections Epstein Barr Virus gateway
