Complement

Question 1

Functions of all complement pathways

Answer 1

Opsonophagocytosis
Inflammation
Lysis

Question 2

First serine protease in classical pathway

Answer 2

C1r (also C1s)

Question 3

3 proteins that make up the C1 complex

Answer 3

C1r, C1q, C1s

Question 4

C1 complex (via C1q) binds these 3 types of antibodies

Answer 4

IgM, IgG1, and IgG3

Question 5

Part of C1 complex that recognizes antibodies bound to the surface of bacteria
Or C-reactive protein in the absence of Ab

Answer 5

C1q

Question 6

Protein that cleaves C4 into C4a and C4b in the classical complement pathway

Answer 6

C1s

Question 7

Does C4a or C4b bind to the pathogen surface after C4 cleavage?

Answer 7

C4b

Question 8

Classical C3 convertase

Answer 8

C4bC2a

Question 9

Part of C3 that is a powerful chemoattractant

Answer 9

C3a

Question 10

Part of C3 that is a powerful opsonin and coats pathogens for receptor recognition

Answer 10

C3b

Question 11

This bond is exposed after cleavage of C3 and is rapidly hydrolyzed if it does not interact with either hydroxyl or amino groups on the surface of a pathogen

Answer 11

Thioester bond
This limits the diffusion of C3b and potential interaction with healthy host cells

Question 12

Protein on macrophage that binds C3b deposited on bacterium

Answer 12

CR1 (complement receptor 1)

Question 13

Opsonin that binds to complement receptor (CR1) on macrophages

Answer 13

C3b

Question 14

Classical C5 convertase

Answer 14

C4bC2aC3b

Question 15

Anaphylatoxins produced in the classical complement pathway which increase vascular permeability, establish a strong chemotactic gradient (recruit immune cells), and also cause smooth muscle contraction and release of histamine from mast cells

Answer 15

C3a and C5a

Question 16

Part of C5 that is a chemoattractant

Answer 16

C5a

Question 17

Part of C5 that binds to C6 to initiate MAC formation

Answer 17

C5b

Question 18

Complement protein that polymerizes to form a transmembrane channel that compromises the integrity of cell membranes

Answer 18

C9

Question 19

Lectin pathway of complement uses these 2 proteins which bind directly to microbial sugars
Are structurally similar to C1q

Answer 19

Mannose-binding lectins or Ficolins

Question 20

Serine proteases in the lectin complement pathway

Answer 20

MASP-1 and MASP-2

Question 21

Mannose-binding lectin is synthesized by these cells

Answer 21

Hepatocytes

Question 22

Protein that acts as an opsonin by binding to mannose-containing carbohydrates of pathogens and triggers the lectin pathway of complement

Answer 22

Mannose-binding lectin

Question 23

Process that allows the thioester bond of C3 to be hydrolyzed without cleave into C3a and C3b, creating a protein known as iC3

Answer 23

Tickover

Question 24

Protein in the alternative complement pathway that binds Factor B

Answer 24

iC3

Question 25

Protein in the alternative complement pathway that binds iC3

Answer 25

Factor B

Question 26

Protein in the alternative complement pathway which binds iC3 and Factor B, cleaving Factor B into Ba and Bb, forming soluble iC3Bb

Answer 26

Factor D

Question 27

C3 convertase of the alternative complement pathway

Answer 27

C3Bb

Question 28

Protein that binds C3b and changes its conformation, allowing Factor I to cleave and inactivate it

Answer 28

Factor H

Question 29

Protein that cleaves C3b into iC3b, inactivating it, after conformational change by Factor H

Answer 29

Factor I

Question 30

2 plasma proteins that regulate the complement cascade

Answer 30

C1 inhibitor and Factor H/I

Question 31

Membrane protein that stabilizes C3bBb and extends its life on the surface of a pathogen, increasing C3b opsonization

Answer 31

Properdin (Factor P)

Question 32

Membrane protein that removes Bb from C3bBb, making the alternative C3 convertase inactive

Answer 32

Decay accelerating factor (DAF)

Question 33

Membrane protein that removes Bb from C3b and allows Factor I to cleave and inactivate C3b

Answer 33

Membrane cofactor protein (MCP)

Question 34

2 proteins expressed at the surface of healthy host cells to prevent the alternative pathway from progressing

Answer 34

DAF and MCP

Question 35

Function of Properdin (Factor P)

Answer 35

Stabilizes C3bBb

Question 36

Function of decay-accelerating factor (DAF)

Answer 36

Removes Bb from C3bBb

Question 37

Function of membrane cofactor protein (MCP)

Answer 37

Removes Bb from C3b, allowing Factor I cleavage

Question 38

Initiator of the classical pathway

Answer 38

Either antibody (IgM or IgG) or C-reactive protein

Question 39

Initiator of the lectin complement pathway

Answer 39

Either mannose-binding lectin or ficolin

Question 40

Initiator of the alternative complement pathway

Answer 40

C3

Question 41

Pathway of complement that:
Does not require Ab
Does not require microbial sugar recognition
Does require inhibitors to prevent attack of self cells

Answer 41

Alternative pathway

Question 42

2 functions of type I interferons (IFN alpha and beta)

Answer 42

Induce resistance to viral replication in all cells
Activate NK cells to kill virus-infected cells

Question 43

Activating receptor on natural killer cells that sends strong activating signal into NK cells; overcomes the natural inhibitory signals

Answer 43

NKG2D

Question 44

2 classes of inhibitory and activating receptors on NK cells

Answer 44

Immunoglobulin-like receptors
Lectin-like receptors

Question 45

Inhibitory NK cell receptors naturally bind this and receive a negative signal

Answer 45

Host MHC

Question 46

Virus-infected cells down regulate this protein, and NK cell loses its negative signal

Answer 46

MHC

Question 47

Virus-infected cells express this protein at their surface, which binds activating receptor NKG2D to provide a positive signal

Answer 47

MIC protein

Question 48

Virus-infected cells express that MIC protein at their surface which binds to this

Answer 48

NKG2D (activating receptor; positive signal)