Complement- Regal Flashcards
What is complement?
A group of plasma proteins that acts as an auxiliary system in immunity on its own AND in conjunction with humoral immunity
What are the specific functions of complement?
Lysis Opsonization Mediators of inflammation Solubilization and clearance of immune complex/ apoptotic cells *augments stimulation of the B cell
What receptor augments stimulation of the B cell to increase humoral immune response?
CR2
What begins the classical activation of complement?
Antibody binds antigen
C1q binds antibody
C1r self-activates and activates second C1r, both activate C1s
This complex is called C1 esterase (C1qr2s2)
What components make up the C3 convertase in the classical pathway?
C4b2a
What components make up the C3 convertase in the alternative pathway?
C3bBb
***What proteins covalently bond to surfaces?
C4b and C3b
What is the membrane attack complex? What molecules form the membrane attack complex?
Transmembrane channel that allows passage of ions and lysis of the cell
C5b+C6
+C7
+C8
+C9
What even prevents the insertion and formation of MAC?
C5b-7 binding to S protein in the fluid phase
What 3 things limit complement activation?
- Short half life or the enzymes formed
- Properties of non-activator surfaces
- Inhibitors (fluid phase and membrane bound)
What molecules are responsbile for the clearance of immune complexes and apoptotic cells?
C1qr2s2
C4 and C2
C3
What molecules of complement are responsible for inflammation and T-cell regulation?
C3a and C5a
What molecule is responsible for Opsoninsation and amplifying adaptive immunity
C3b
What is factor H?
a fluid phase inhibitor of C3 convertase
If C3bBb is floating around, it binds to it and dissociates the Bb inactivating it
decay acceleration of the convertase
Can also bind C3b that is bound to membranes with sialic acid (our membranes)
What is Factor I?
Factor I can degrade C3b that binds to membranes with sialic acid (need Factor H bound 1st as a cofactor)
What will deficiencies of complement control proteins lead to? (in general)
uncontrolled activation of the complement system!
Lysis or..
Consumption of the complement components leading to the consequences of secondary complement deficiency (IC disease and infecitons)
C1 InH deficiency
Normal prevents activation of C1 esterase
Deficiency = herediatary angioedema
Deficiency in DAF
Increased susceptibility of erythrocytes to MAC-mediated lysis
What is the role of CR1?
Transport of immune complexes by RBC
promotes immune adherence,binding of opsonized microbes to primate RBCs
What is the role of CR2?
Augment stimulation of the B-cell (high affinity for EBV envelope protein)
What are CR3 and CR4 involved in?
Found on monocytes, macrophages, PMN, NK cells, and T cells
involved in phagocytosis and cell adhesion
Binds immune complexes
