Complement System

Question 1

Complement proteins

Answer 1

plasma proteins produced mainly in the liver, complement action of antibodies in destruction of bacteria, ridding the body of foreign substances (antigens) etc

Question 2

Classical pathway

Answer 2

Antibodies (igG or IgM) are recognized by complement proteins (C1 complex)

Question 3

When the C1 complex interacts with antibodies what part of the complex recognizes the antibody, activating what complement proteins that have what substrates

Answer 3

C1Q, activates C1r cleaving C1s and converting it to an enzyme whose substrates are C2 and C4

Question 4

When C4 protein is cut what product interacts with the antigen surface, what does it complex with

Answer 4

C4b, C2a creating the C4BC2a complex

Question 5

C4BC2a complex is also known as what enzyme, what is its function

Answer 5

C3 convertase, catalyzes the protelytic cleavage of C3 and holds C3b

Question 6

When C4bC2a/C3b is formed what is the substrate it interacts with, what stays bound

Answer 6

C5, C5b

Question 7

T/F: When C5b stays bound it stays on the C4bC2a/C3b complex

Answer 7

False: C5b stays bound to the pathogen

Question 8

What proteins does C5b recruit, which one opens a pore in the antigen

Answer 8

C6,C7,C8,C9/C9

Question 9

What does the pore created in the antigen cause

Answer 9

H20 and ions enter the pathogen causing the cell to swell and lyse

Question 10

lectin

Answer 10

cell surface protein that recognizes and bids sugars or oligosacchardies

Question 11

In the lectin pathway what recognizes pathogens

Answer 11

Mannose binding lectin (MBL)

Question 12

T/F: Mannose residues are typically not found on self proteins allows MBL to float freely

Answer 12

True

Question 13

Ficolins

Answer 13

plasma proteins that coat different species of bacteria causing complement proteins to attack (opsonization), recognizes NAG

Question 14

What does MBL typically complex with

Answer 14

Mannose Associated Serine Porteases (MASP), MASP-2 cleaves c4 and c2 forming C4bC2a complex

Question 15

When does the lectin pathway become analogous to the classical pathway

Answer 15

Once the C4aC2b complex is formed leading to cleavage of C3 and C5

Question 16

What occurs in initiation of the alternative pathway

Answer 16

circulating C3 slowly cleaves itself and binds to a pathogen, factor B binds to C3B and is cleaved to Bb

Question 17

C3b and Bb come together to create what enzyme, what is the result of this

Answer 17

C3 convertase, many C3bs cover a pathogen eventaully causing a C5 to be cleaved and C5b to be bound

Question 18

T/F: The classical, leptin, and alternative pathways all converge on C5b is bound

Answer 18

True

Question 19

In regulation of the classical pathway what protein prevents complement activation

Answer 19

C1 esterase inhibitor (C1INH)

Question 20

In regulation of the classical pathway which proteins cause dissociation of C4b2a

Answer 20

C4 binding protien (C4BP), DAF, CR1/CD35, MCP

Question 21

In regulation of the classical pathway which protein cleaves C4b after C2a leaves

Answer 21

Factor I

Question 22

In regulation of the alternative pathway which protein binds to C3bBb complex and displaces Bb

Answer 22

Factor H

Question 23

As a major function of complement which protein causes opsonization

Answer 23

C3b

Question 24

As a major function of complement which proteins cause anaphylatoxin production

Answer 24

C5a,C3a,C4a

Question 25

As a major function of complement which proteins cause cell lysis

Answer 25

C5b-C9

Question 26

What are other minor activities of complement

Answer 26

enhancement of B-Cell receptors, removal of immune complexes, removal of necrotic cells and subcellualr membranes