module 08 section 01 (complement)

Question 1

is the complement system a part of the innate or the adaptive immune system?

Answer 1

innate

Question 2

recall: what is an opsonin?

Answer 2

a substance that binds to foreign microorganisms or cells, making them more susceptible to phagocytosis

Question 3

do opsonins play an important role in inflammation or defense?

Answer 3

both

Question 4

what can opsonins do to foreign particles?

Answer 4

coat them to tag/mark them for engulfment by APCs

Question 5

who discovered complement proteins? how?

Answer 5

• Jules Bordet
• heated serum and found them
• found that the heat-stable component was responsible for immunity against specific microorganisms (antibody)
• found that the heat-sensitive component was responsible for non-specifc antimicrobial activity (complement proteins)

Question 6

how do complement proteins enhance the killing of bacteria?

Answer 6

by binding to bacteria-bound anitbodies

Question 7

complement proteins are “heat liable”, what does this mean?

Answer 7

if they’re heated they lose their effector activity

Question 8

what is complement composed of?

Answer 8

30 glycoprotein macromolecules that circulate in their inactive forms until they’re activated

Question 9

what happens once complement glycoprotein macromolecules are activated? (4)

Answer 9

• lysis of targets
• opsonization of particulate antigens
• activation of inflammatory responses
• clearance of immune complexes

Question 10

what are the primary synthetic sources of the glycoprotein macromolecules? (3)

Answer 10

monocytes, macrophages and hepatocytes

Question 11

what are the three main functions of complement glycoproteins?

Answer 11

activation pathways, regulation pathways and membrane receptors

Question 12

what are the three activation pathways that complement glycoproteins are involved in?

Answer 12

• classical pathway
• alternative pathway
• lectin pathway

Question 13

what do complement glycoproteins regulate?

Answer 13

complement activation

Question 14

explain the role of complement glycoproteins as membrane receptors

Answer 14

proteins coating a pathogen can bind to membrane receptors resulting in phagocytosis of the foreign entity

Question 15

complement activation can be divided into ___ components?

Answer 15

2

Question 16

what is the first component of complement activation?

Answer 16

• there’s three distinct pathways that result in the production of C5b proteins
• all three converge to result in inflammation, opsonization and lysis

Question 17

what are C5b proteins?

Answer 17

• important fragment forming the first part of the complement system
• plays an important role in the target cell killing process

Question 18

explain how complement systems result in inflammation

Answer 18

activation of the complement system produces proteins having the ability to recruit and activate inflammatory cells

Question 19

explain how complement systems result in opsonization

Answer 19

activation of the complement system produces proteins having the ability to opsonize pathogens and immune complexes

Question 20

explain how complement systems result in lysis

Answer 20

activation of the complement system produces membrane attack complexes (MACs) which leads to the killing of pathogens by cell lysis

Question 21

does the classical pathway require antibodies

Answer 21

yes

Question 22

what is the classical pathway activated by?

Answer 22

immune complexes (Ag-Ab) involving human Igs IgM, IgG1, IgG2 and IgG3

Question 23

does the lectin pathway require antibodies?

Answer 23

no

Question 24

what is the lectin pathway activated by?

Answer 24

mannan, which is expressed only on bacteria and viruses

Question 25

does the alternative pathway require antibodies?

Answer 25

no

Question 26

what is the alternative pathway activated by?

Answer 26

• non-Ab substances such as lipopolysaccarides, polymers or venom factors
• these substances can origionate from microorganisms (pathogens) or human IgA and IgE aggregates (non-pathogens)