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33 Cards in this Set

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In general terms, what is complement?
Complement is a system of proteins that interact to play a role in humoral immunity and inflammation.
What are five functions of complement?
Complement can directly opsonize foreign material for phagocytosuis after antibody activation (C3 component). Can participate directly in killing some cells and microorganisms, and can regulate inflammation.

It also neutrolizes viruses, and is involved in the solubilization of immune complexes.
What are the three pathways of complement?
Classical pathway, MB-lectin pathway, alternative pathway
What is the main end product of complement activation and what does it do?
The membrane attack complex is the end result product and it is a lipid soluble pore structure that causes osmotic lysis of cells.
What complement pathway is associated with antibody directed mechanisms?
the classical pathway
what antibodies are recognized to initiate classical pathway of complement?
Complement recognizes antibody antigen complexes and requires one IgM or two IgG molecules.
In classical pathway complement, to what protein do the antigen-antibody complexes bind?
They bind to C1 which starts the cascade.
What is the role of mannose binding lectin.
Mannose Binding Lectin plays a similar role to activated C1 in that is cleaves C4 into C4a and C4b.
What causes the alternative pathway of the complement system?
Activation occurs as a result of binding directly to the surface of an infectious organism.
In the classical pathway what does C1 cleave?
It cleaves C2 and C4
In the classical pathway, what enzyme is the C3 convertase?
C4b2b, written in some literature as C4b2a.....
what is C4b2b?
In the classical pathway it is the C3 convertase. It can cleave many molecules of C3 and is the site of amplification of the complement pathway.
How does C4b2b bind to cells?
It binds to cell membranes covelently.
what is C3?
C3 is a heat stable glycoprotein and is responsible for the destinction `between "self" and "non-self"
"self" surfaces limit C3 deposition, whereas "non self" surfaces allow rapid c3 deposition.
In a general sense, what activates c3?
The classical pathway, the alternative pathway, thrombin, plasmin, and tissue proteases.
What is the role of C3a?
It is an anaphylatoxin causing mast cell degranulation and mediates vascular leakage.
What is the role of C3b?
C3b causes opsonization and immunologic adherence via specific receptors for this component. C3b receptors are found on granulocytes, monocytes, lymphocytes and erythrocytes.
C3b combines with what to form what (the classical c5 convertase)
C3b combines C4b2b to make C4b2b3b (the classical C5 convertase)
What is classical pathway C5 convertase?
(c4b2b3b)
what is the critical step in complement?
the activation of C3
what are the plasma proteins associated with the activation of C3 in the alternative pathway?
properdin (stabilizes C3bBb) , Factor B (similar to C2), and Factor D (cleaves factor B (creating active factor Bb)
What is the C3 convertase of the alternative pathway?
C3bBb+P(properdin)
If C3 convertase cleaves C3 to C3a and C3b how is there C3b in the alternative pathway C3 convertase?
C3 spontaneously degrades at a low rate to form C3a and C3b.
Describe the alternative pathway.
C3b binds to factor B allowing Factor D to cleave Factor B into Bb and Ba. Bb stays associated with C3b and joins also with properdin which stabalizes the molecule. The joining of another C3b changes the C3 convertase to a C5 convertase (C3bBb3b(P))
C5 convertase of alternative pathway?
C3bBb3b(P)
What is the role of C5 convertase in the complement system?
C5 convertase converts C5 into C5a and C5b
what is the role of C5b in the complement system?
C5b combines with C6, C7, C8 and C9 to form membrane attack complex (MAC)
what is the role of C5a in complement system?
C5a is an anaphylatoxin and chemotactic factor. increasing vascular permiability and causes vasodilation by inducing mast cells to release histamine.
in general terms, what is the role of C5a and C3a?
inflammation, caused by the recruitment and activation of leukocytes
role of C3b in the complement system?
besides it's role in the convertases C3b, when bound to a microbial surface may aid in opsonization of the microbe by macrophages. Complement receptor 1 (CR1) on macrophages allows the engaging of C3b covered microbes.
role of Complement receptor 1 (CR1)?
CR1 on macrophages allows the engaging of C3b covered microbes.
C5-8(9) deficiency leads to what?
Recurrent neisseria infections
What is CH50?
Total Hemolytic complement -- CH50 reflects the ability of serum complement to lyse sheep red blood cells (RBCs); its value is the reciprocal of the dilution of serum to lyse 50% of antibody coated sheep RBCs. Reduction of the CH50 occurs when individual complement component(s) are deficient or consumed.