Complement System

Question 1

The major humoral effector mechanism of immune resposne

Answer 1

complement system

Question 2

Which is the only antibody-dependent complement activation pathway?

Answer 2

Classical (alternative and lectin are antibody-INdependent)

Question 3

activation of complement system results in the generation of these 4 major immunobiological activities

Answer 3

1. anaphylatoxins
2. chemoattractants/chemotaxis
3. Memembrane attack complex (MAC attack!)
4. Opsonins

Question 4

Which pathway is considered a pathogen associate molecular pathway? (PAMP?)

Answer 4

Mannose binding lectin pathway, which minds to a terminal mannose

Question 5

what is the humor effector mechanism initiated by?

Answer 5

Soluble molecules (classical requires antibody, connecting it to adaptive immune system)

Question 6

anaphylaxis

Answer 6

acute systemic inflammatory response

Question 7

these factors induce smooth muscle contraction and degranulation of mast cells and basophils

Answer 7

Anaphylatoxins

Question 8

These factors act on neutrophils and monocytes to direct their migration to the antigenic stimulus

Answer 8

Chemoattractants/chemotoxins (C5)

Question 9

This complex produces holes in the membranes of bacterial pathogens and cells, and is comprised of which molecules?

Answer 9

Membrane attack complex. Made up of C5b, C6, C7, C8, C9n

Question 10

The major opsonin of the complement system

Answer 10

C3b (a little on C4b)

Question 11

All three pathways converge at which step to form what?

Answer 11

Converge at C3b to then activate membrane attack complex

Question 12

Activator of C1q

Answer 12

IgM (secretes as pentamer) and IgG

Question 13

Serine proteases when activated

Answer 13

C1r and C1s

Question 14

3 major plays of Classical pathway

Answer 14

C1, C4, C2

Question 15

How many of the globular heads of C1q must bind to the Fc portions of antibodies on bacteria?

Answer 15

2 globular heads out of 6.

Question 16

C3 convertase of classical pathway

Answer 16

C4b2a (C4b + C42a)

Question 17

the bond C4b makes with surface of bacteria

Answer 17

labile thioester bond

Question 18

C3b has same opsinon function as

Answer 18

IgG

Question 19

C3 convertase of classical pathway (C4b2a) function as an enzyme

Answer 19

cleaves C3 to generate C3b (large) and C3a (small)

Question 20

Alternative pathway is activated by a small amount of

Answer 20

C3b (can be generated from lectin or classical pathway)

Question 21

Mannose binding lectin pathway has overall structural homology to C1q, except that it binds to

Answer 21

terminal mannose sugar of bacteria

Question 22

Two molecules associated with MBL structure and 2 important properties

Answer 22

MASP-1, MASP-2

1) antibody independent
2) like C1r and C1s, they are serine proteases

Question 23

In alternative pathway, C3b bound to bacteria provides a binding site for

Answer 23

Factor B

Question 24

Major players in alternative pathway

Answer 24

Factor B and D

Question 25

This factor circulate in its active form and cleaves B into Bb

Answer 25

Factor D

Question 26

C3 convertase of alternative pathway

Answer 26

C3bBb

Question 27

In addition to binding to bacteria to instigate the alternative pathway, what else can C3b do?

Answer 27

Acts as an opsonin and can bind with C3 convertases

Question 28

C5 convertases

Answer 28

Classical/MBL: C4b2a3b Alternative: C3bBb3b *final step in complement cascade*

Question 29

C5 convertases activity

Answer 29

Cleave C5 into C5a and C5b

Question 30

Binds to antigen surface and begins formation of MAC

Answer 30

C5b

Question 31

What is most important deficiency in complement pathway

Answer 31

C3

Question 32

Promote the movement of leukocytes from blood into soft tissue and changes blood flow so that increase adhesion molecules are expressed

Answer 32

Anaphylatoxins

Question 33

Deficiency of MAC is only a problem when dealing with this one type of bacteria

Answer 33

Nysteria

Question 34

Recurrent infections from C3 deficiecny

Answer 34

Pyogenic Infection (looks similar to C3b deficiency)

Question 35

Properdin is a stimulatory regulatory molecule found in solution (soluble) that stabilizes which complex?

Answer 35

C3bBb (C3 convertase of alternative pathway)

Question 36

C1 inhibitior (C1-INH) stops complement activation at which stage?

Answer 36

C1 activation: dissociates C1q from (C1r+C1s)

Question 37

individuals that lack C1-INH develop this serious condition

Answer 37

Hereditary Angioneurotic Edema (usually see the accumulation of fluids in the larynx)

Question 38

C4 -binding protein (C4BP) inhibits which stage of complement activation?

Answer 38

Classical and Mannose C3 convertase. | Dissociates C4b2a ---> (C4b + C2a)

Question 39

Cofactor for Factor I

Answer 39

C4BP

Question 40

degrades C4b and C3b using C4BP or H as cofactor by proteolysis

Answer 40

Factor I

Question 41

Why does Factor I cleave C4b and C3b?

Answer 41

so that those molecules wont re react with C2a and Bb respectively

Question 42

An increase in [C3b] circulating is due to a deficiency in this

Answer 42

Factor I (cleaves C3b)

Question 43

Dissociates alternative pathway C3 convertase into C3b and Bb

Answer 43

Factor H

Question 44

Two types of regulatory molecules/ inhibitors in complement pathway

Answer 44

soluble (found in solution) and membrane associate (found on human cell membranes)

Question 45

3 regulatory membrane bound molecules

Answer 45

1. DAF (decay accelerating factor) 2. CD59 3. MCP (membrane co-factor protein)

Question 46

Disease associated with absence of DAF and CD59

Answer 46

Paroxysmal Nocturnal Hemoglobinuria = destruction of RBC

Question 47

DAF and CD59 are bound to membrane by

Answer 47

GPI linkages

Question 48

DAF and CD59 protect against

Answer 48

Membrane attack complex (MAC)

Question 49

Why can't RBC block MAC formation?

Answer 49

Not nucleated (nucleated cells have regulatory protective mechanism and can also repair damage to cell membrane)

Question 50

Receptor for C3b and C4b

Answer 50

CR1

Question 51

Interaction of CR1 with its ligands stimulate

Answer 51

phagocytosis, erythrocyte transport of immune complexes and promotes C3b and C4b decay

Question 52

how do CR1 on RBCs work?

Answer 52

Bind to immune complex in blood and eliminates it through the spleen; RBC returns to circulation

Question 53

Main Fc receptor that promotes phagocytosis

Answer 53

Fc gamma R1 (for antibody IgG1)

Question 54

Fc receptor binds to

Answer 54

Fc portion of an antibody that is bound to an antigen

Question 55

Fc gammaR1 receptor for which antibody

Answer 55

IgG

Question 56

Fc epsilonR1 is receptor for which antibody

Answer 56

IgE

Question 57

Fc epsilonR1 is found on what cells

Answer 57

mast cells and basophils

Question 58

Fc gammaR1 is found on what cells

Answer 58

phagocytic cells (macrophages and neutrophils)