2nd line of defense: complement basic properties

Question 1

what is the complement cascade system

Answer 1

enzyme cascade system consist of 30+ serum/plasma proteins involved in immune and inflammatory response

Question 2

difference of plasma and serum

Answer 2

plasma- separated from unclotted whole blood. serum separated from clotted blood no fibrinogen

Question 3

where are complements produced

Answer 3

liver

Question 4

complements exist as

Answer 4

inactive forms (some are protease enzymes called zymogens). C3 is inactive C3a and C3b is active

Question 5

how does complement work as acute phase protein/reactant

Answer 5

increase of APR/APP can be detected in blood/serum during acute phase of inflammation. eg C reactive protein

Question 6

define biological amplification

Answer 6

small initiating stimulus triggers a rapid and vigorous response to an infection

Question 7

purpose of enzymatic rxns in regards to complement

Answer 7

activations sequential complement system. each rxn cleaves inactive from to 2 active form

Question 8

which fragment diffuses away

Answer 8

smaller fragment “a” diffuses away. bigger “b” will remain close to site of activation

Question 9

consequences of complement activation

Answer 9

inflammation, chemotaxis, opsonization, MAC

Question 10

Describe how anaphylatoxins cause inflammation

Answer 10

anaphylatoxins (C3a and C5a) bind to receptors (C3aR C5aR) on mast cells & basophils leading to degranulation w/ release of vasoactive mediators like histamine

Question 11

chemotaxis

Answer 11

chemotactic agents C3a and C5a diffuse away creates [gradient] attracting WBC like phagocytes

Question 12

opsonization

Answer 12

opsonin C3b coats surface of microbes rendering them easily capture by phagocytes

Question 13

Membrane attack complex

Answer 13

C5-C9 join to from MAC can puncture microbe’s membrane leading to lysis

Question 14

how is the alternate pathway initiated

Answer 14

C3 binds to surface of microorganism

Question 15

how is classical pathway activated

Answer 15

C1 binding to receptor on antibody IgG/ IgM that is complexed with specific antigen (antigen-antibody or immune complex)

Question 16

what is the most direct and simplest pathway

Answer 16

alternate

Question 17

how is the lectin pathway initiated

Answer 17

C4 binding to mannose-binding protein that is attach to microbial surface

Question 18

what is mannose

Answer 18

type of sugar found on microbe surfaces

Question 19

example of APR/APP acute phase protein/reactant

Answer 19

bacteria induce macrophage to make IL-6 which acts on hepatocytes to induce synthesis of acute phase proteins. CRP binds phosphoryline cholie on surface actin as opsonin and complement activator