Antibody Structure and Function

Question 1

what are the two regions of an antibody?

Answer 1

the constant and variable regions

Question 2

what are the 2 chains in an antibody?

Answer 2

the light and heavy chains

Question 3

what holds the chains of an antibody together?

Answer 3

disulphide bonds

Question 4

T/F the 2 light chains / the 2 heavy chains are identical to each other (both light are the same and both heavy are the same)

Answer 4

true

Question 5

gene rearrangement in antibodies typically occurs in what region?

Answer 5

the variable region

Question 6

why does gene rearrangement occur in the variable region and not the constant region?

Answer 6

because it is the region that binds to the antigen and if the constant part was changed, it would change the function of the antibody

Question 7

can the heavy chains be functional without the light chains attached?

Answer 7

no

Question 8

what are the 2 forms of light chains found in humans?

Answer 8

kappa and lambdid

Question 9

can you have a kappa light chain on one side and a lambdid light chain on the other?

Answer 9

no

Question 10

compare/contrast lambdid and kappa light chains

Answer 10

same function, slightly different constant region

Question 11

what is the FAB region? where is it located?

Answer 11

antigen binding region; at top ends of Y structure

Question 12

what is the FC region? where is it located?

Answer 12

effector function region; at bottom of Y structure

Question 13

what happens if the FC region is changed?

Answer 13

class switch

Question 14

what region defines the class of the antibody?

Answer 14

the FC region

Question 15

describe the roles of FAB and FC in terms of an incoming protein

Answer 15

FAB recognizes it and the FC region chooses what to do about it

Question 16

T/F each class of antibody has a unique FC region and unique function

Answer 16

true

Question 17

which class(es) of antibodies are monomers?

Answer 17

IgD, IgE, IgG

Question 18

which class(es) of antibodies are dimers?

Answer 18

IgA

Question 19

which class(es) of antibodies are pentamers?

Answer 19

IgM

Question 20

the structure of a pentamer can fold so that ___ stick up

Answer 20

FC regions

Question 21

antibodies in a pentamer are connected by what type of chain?

Answer 21

J chain

Question 22

do antibodies kill?

Answer 22

no, but they help other things kill

Question 23

what are the 4 functions of antibodies?

Answer 23

1. opsonization for phagocytosis
2. fixing the complement
3. blocking attachment
4. neutralize toxins

Question 24

what is the role of opsonization for phagocytosis?

Answer 24

facilitates uptake of bacteria by neutrophils/macrophages by creating a “candy coating” around bacteria

Question 25

the complement cascade results in ___

Answer 25

MAC attack (membrane attack complex)

Question 26

what is the function of MAC attack?

Answer 26

pokes holes in cells

Question 27

the complement cascade is initiated by the ____ pathway

Answer 27

classical (antibody involved)

Question 28

what are 3 requirements for fixing the complement?

Answer 28

1. 2 antibodies must be involved 2. they must be appropriately spaced apart 3. both must have FAB region down on cell surface

Question 29

a molecule called ___ (which has many different arms) will bind only to the FC region

Answer 29

C1

Question 30

how many C1 molecules are needed to fix the complement?

Answer 30

2

Question 31

why do antibodies need to be a specific distance apart to fix the complement?

Answer 31

the C1 is not flexible to conform to bind at whatever distance apart the antibodies are

Question 32

the complement cascade includes everything from C__ to C__. Which are most important in killing bacteria?

Answer 32

1-9 ; C5-C9

Question 33

why are C5-C9 the most important in killing bacteria?

Answer 33

they form a complex that makes a hole in the lipid bilayer, leading to osmotic flow into cell and lysis (MAC)

Question 34

how can antibodies block attachment of viruses, some bacteria, and extracellular protazoa?

Answer 34

FAB regionbinds to protein on surface of virus, preventing the virus from being able to bind due to exposed FC region of attached antibody q

Question 35

how do antibodies neutralize toxins?

Answer 35

bind to toxins, preventing them from binding to any toxin receptors

Question 36

antibodies can also aggregate toxins into groups called ___

Answer 36

immune complexes

Question 37

immune complexes can be removed by cells in the ___ and __ (organs)

Answer 37

liver and spleen

Question 38

what is the most common class of antibody?

Answer 38

IgG

Question 39

what are the 4 functions of IgG?

Answer 39

1. fixes the complement well 2. great at candy coating for phagocytosis 3. blocks attachment well 4. neutralize toxins

Question 40

what is the only antibody class to pass through the placenta to provide early protection?

Answer 40

IgG

Question 41

what is ivIg? why does it exist?

Answer 41

intravenous Ig agammaglobulinemia; no antibodies in the blood

Question 42

IgM makes up __% if the Ig pool

Answer 42

10

Question 43

what are the 3 functions of IgM?

Answer 43

1. great at fixing complement 2. great at blocking attachment 3. good at blocking toxins

Question 44

why is IgM good at blocking attachment and blocking toxins?

Answer 44

because it is so big

Question 45

why does IgM fix complement so well?

Answer 45

its FC regions stick up making antibodies exact distance apart to fix C1

Question 46

why is IgM not able to opsonize for phagocytosis?

Answer 46

5 congregated FC regions will not fit into FC receptor

Question 47

is IgM or IgG made first? why?

Answer 47

IgM, because it does not require a class switch

Question 48

IgA makes up __- % of the Ig pool

Answer 48

15

Question 49

IgA protects what areas of the body?

Answer 49

mucous membranes in lungs and gut

Question 50

what are the 2 functions of IgA?

Answer 50

1. blocking attachment | 2. neutralizing toxins

Question 51

why cant IgA fix complement well?

Answer 51

the FC regions of the dimer are unavailable

Question 52

why cant IgA opsonize for phagocytosis?

Answer 52

dimer cant fit into FC receptor

Question 53

why is IgA good at neutralizing toxins?

Answer 53

the dimer aggregates well

Question 54

what are 2 reasons why someone might have high levels of IgE?

Answer 54

1. they are atopic (many allergies) | 2. a parasitic infection with roundworms

Question 55

IgE binds to ___ on mast cells

Answer 55

FcER ( FC epsetion receptor )

Question 56

what functions are IgE good at?

Answer 56

none of the typical, because it is bound to the mast cell and not availble

Question 57

IgD makes up ___ % of the Ig pool

Answer 57

basically zero

Question 58

what is the function of IgD?

Answer 58

not well known, but maybe involved in B cell activation

Question 59

what are monoclonal antibodies and their purpose?

Answer 59

antibodies typically produced in a lab

Question 60

monoclonal antibodies are almost always which Ig? why?

Answer 60

IgG; long lifespan

Question 61

finding monoclonal antibodies in circulation can help diagnose ___

Answer 61

cancer originating from expansion of single b cell

Question 62

extracellular bacteria are fought by __ and __

Answer 62

innate immune system and antibody

Question 63

intracellular bacteria are fought by __ and are not dependent on __

Answer 63

cell-mediated immunity; antibody

Question 64

what is the role of the complement if an extracellular bacteria has never been seen before?

Answer 64

binds directly to bacteria and kill it a bit

Question 65

what is the role of c3b if an extracellular bacteria has never been seen before?

Answer 65

activates the alternate pathway that activates neutrophils to eat it

Question 66

the alternate pathway will also respond to ___ if an extracellular bacteria has never been seen before

Answer 66

toll-like receptors

Question 67

toll-like receptors cause killing by (2)

Answer 67

1. reactive oxygen and nitrogen interediates | 2. superoxide, h202, NO

Question 68

do macrophages have defensins?

Answer 68

no

Question 69

what is the role of the dendritic cell if a bacteria has never been seen before?

Answer 69

take up antigen for presentation at the lymph nodes to activate the adaptive immune response

Question 70

what will the antibodies do if an extracellualr bacteria has been seen before?

Answer 70

will bind, opsonize and fix the complement

Question 71

what is post strep glomerulonephritis?

Answer 71

decomposition of antibody/antigen complex in the kidney glomeruli leads to destruction of the kidney tissue

Question 72

decomposition of the antibody/antigen complex in the kidneys leads to activation of __ and __

Answer 72

1. frustrated phagocytosis | 2. activation of complement

Question 73

frustrated phagocytosis is used to kill ___ infections

Answer 73

parasitic

Question 74

what is post strep rheumatic fever?

Answer 74

IgG response to strep A antigen cross reacts with the heart, damaging the valves and myocardium

Question 75

Th-1 is involved in the __ response

Answer 75

inflammatory

Question 76

can IFN -y activate infected macrophages?

Answer 76

not very well

Question 77

when IFN-y activates uninfected macrophages, they release ___ and ___

Answer 77

IL-1 and INF

Question 78

what is the role of TNF in fighting infection?

Answer 78

brings more macrophages to the site

Question 79

what are the main cells affected by HIV?

Answer 79

CD4+ T helper cells

Question 80

in the long run, what can happen to a granuloma if there are not enough CD4+ t cells at the site?

Answer 80

it can degrade and release the infection