Antibodies and Antigens (Lec 6)

Question 1

Are antibodies and immunoglobulins interchangeable terms?

Answer 1

yes

Question 2

most abs are found in the third fastest migrating group of globulins called what?

Answer 2

gamma globulins

Question 3

What are the effector properties of the light chain part of abs?

Answer 3

direct antibacterial activity; immunomodulation

Question 4

What is the effector property of the heavy chain part of abs?

Answer 4

toxin neutralization

Question 5

What is the effector property of the variable region part of abs?

Answer 5

reduced damage to host from inflammatory response

Question 6

What are the effector properties of the Ab combining site (Fab) part of abs?

Answer 6

organized T-cell response; opsonization

Question 7

What is the effector property of the constant regions (Fc region) of abs?

Answer 7

activation of complement

Question 8

Abs have a basic unit of four polypeptide chains - two light chains and two heavy chains. What keeps the chains bound together?

Answer 8

covalent disulfide bridges and non covalent interactions

Question 9

Abs can be proteolytically cleaved to yield how many Fab and Fc fragments?

Answer 9

2 Fab fragments

1 Fc fragment

Question 10

Both H and L chains are divided into V and C regions. What do the V and C regions contain?

Answer 10

V region contains Ag binding site

C region determines fate of the Ag

Question 11

There are five different kinds of H chains which determine what?

Answer 11

the class of antibody (IgM, IgD, IgG, IgE, and IgA)

Question 12

How many toes of L chains are there?

Answer 12

2: k and gamma, each with a MW of 23 kDa

Question 13

True of false?

Each Ab unit can have only k or gamma L chains but not both

Answer 13

true

Question 14

Both H and L chains have intrachain disulfide bridges every __ amino acid residues

Answer 14

90

Question 15

What do intradisulfide bridges create in H and L chains?

Answer 15

polypeptide loops, domains of 110 amino acids

Question 16

The domains domains created by intradisulfide bridges are referred to as what?

Answer 16

Vh, Vl, Ch1, Ch2, etc

Question 17

In regards to secreted IgG, the Ag binding site is formed by the juxtaposition of what two domains?

Answer 17

Vl and Vh

Question 18

True or False?

In regards to secreted IgG, the H chain C regions end in short pieces

Answer 18

false, tall pieces

Question 19

True or false?

In regards to membrane-bound IgM on B cellls, there is one more Ch domain than IgG has

Answer 19

true

Question 20

Membrane-bound IgM on B cell has C-terminal transmembrane and cytoplasmic portions that do what?

Answer 20

anchor the molecule in the plasma membrane

Question 21

IgG is cleaved by what enzyme which results in 2 Fab fragments and an Fc fragment?

Answer 21

Papain

Question 22

This enzyme cleaves IgG and generates a single bivalent antigen-binding fragment, F(ab’)2

Answer 22

Pepsin

note: there are also small peptide fragments as a result of cleavage

Question 23

What is the role of hinge regions in abs?

Answer 23

provides flexibility between in regions between the Ch1 and Ch2 domains

Question 24

The Ig superfamily is a large group of cell surface and soluble proteins that are involved in what?

Answer 24

recognition, binding, or adhesion processes of cells

examples: T cell receptor; MHC molecules; the CD4 receptor of T cells; CD28, a costimulatory receptor on T cells; and the adhesion molecule ICAM-1

Question 25

Compare the on-rate/off-rate of Ig and TCR in regards to Ag binding

Answer 25

Ig - rapid on-rate, variable off-rate | TCR - slow on-rate, slow off-rate

Question 26

What are CDRs?

Answer 26

complemtarity-determining regions from the H and L chain: loops that protrude from the surface of the two Ig V domains and in combination create an Ag-binding region

Question 27

Each CDR is composed of how many antiparallel beta strands?

Answer 27

two; form two beta-pleated sheets held together by a disulfide bond

Question 28

The tightness of Ag-Ab binding is called what?

Answer 28

ab affinity

Question 29

Abs formed in the primary response soon after the injection of an Ag are generally higher or lower in affinity?

Answer 29

lower

Question 30

Abs produced by a memory response have a higher or lower affinity than those in a primary response?

Answer 30

higher affinity

Question 31

True or false? | Affinity of an Ab is critical when the Ag is a toxin or virus and must be neutralized rapidly

Answer 31

true

Question 32

The valence of an Ab is the maximum number of ___ ___ with which it can react

Answer 32

antigenic determinants

Question 33

IgG contain two Fab regions and can bind two molecules of Ag or two identical sites on the same particle, thus having a valence of what?

Answer 33

2

Question 34

Valence is important for binding affinity, as having two or more binding sites for an Ag can dramatically increase or decrease the affinity?

Answer 34

increase

Question 35

The combined effect that results from synergy of the binding strengths of each binding site is called what?

Answer 35

avidity

Question 36

Ab with a low affinity for an Ag determinant but with a large number of binding sites, for example IgM as compared to IgG, can be extremely effective in doing what?

Answer 36

neutralizing a microorganism?

Question 37

True or false? | Polyvalent relates to low avidity of interaction

Answer 37

false, very high avidity of interaction; the more valency present, the more avidity of interaction

Question 38

Match the following stage of B cell development with its pattern of Ig production: stem cell

Answer 38

none

Question 39

Match the following stage of B cell development with its pattern of Ig production: Pre-B cell

Answer 39

cytoplasmic u H chain and Pre-B receptor

Question 40

Match the following stage of B cell development with its pattern of Ig production: Immature B cell

Answer 40

membrane IgM

Question 41

Match the following stage of B cell development with its pattern of Ig production: Mature B cell

Answer 41

membrane IgM, IgD

Question 42

Match the following stage of B cell development with its pattern of Ig production: Activated B cell

Answer 42

low rate Ig secretion; H chain isotype switching; affinity maturation

Question 43

Match the following stage of B cell development with its pattern of Ig production: Ab-secreting cell

Answer 43

high rate Ig secretion; reduced membrane Ig

Question 44

Match the following change in antibody structure to its functional significance in antigen recognition and its effector function: affinity maturation

Answer 44

Antigen recognition: increased affinity Effector function: no change

Question 45

Match the following change in antibody structure to its functional significance in antigen recognition and its effector function: change from membrane to secreted form

Answer 45

Antigen recognition: no change Effector function: change from B cell receptor function to effector function

Question 46

Match the following change in antibody structure to its functional significance in antigen recognition and its effector function: Isotype switching

Answer 46

Antigen recognition: no change Effector function: each isotope serves a different set of effector functions

Question 47

IgA is the most common Ab in what?

Answer 47

mucosal secretions

Question 48

IgM is mainly found in what?

Answer 48

plasma

Question 49

IgE is absorbed on the surface of what?

Answer 49

mast cells

Question 50

IgG penetrates deeper into what?

Answer 50

tissue

Question 51

What is the most abundant Ig in the blood?

Answer 51

IgG

Question 52

True or false? | IgG provides the bulk of immunity to most bloodborne pathogens

Answer 52

true

Question 53

IgG is the only Ab to cross the placenta to provide what type of immunity to the developing fetus and to the infant on its birth?

Answer 53

passive humoral immunity

Question 54

What type of H and L chains do IgG Abs have?

Answer 54

two H gamma chains | either two k or two lambda L chains

Question 55

Subclasses of IgG have slightly different sequences in their H or L chains that result in differences in their functional activities?

Answer 55

H chains

Question 56

The epithelial cell surface receptor for Fc regions (FCRn) of maternal IgG is present where?

Answer 56

in the placenta

Question 57

FCRn does what?

Answer 57

transfers maternal IgG to the fetal circulation

Question 58

True or false? IgA is the major Ig present in external secretions such as colostrum, milk, and saliva where it exists as a 420 kDa dimer

Answer 58

true

Question 59

In addition to the k or lambda L chains and the H alpha chain, the secreted IgA also contains two other polypeptide chains. What are they?

Answer 59

Secretory component (SC) and joining chain (J-chain)

Question 60

SC is part of the poly-Ig receptor involved in the ____ ____ of exocrine IgA and stabilizes IgA against proteolytic degradation

Answer 60

transepithelial transport

Question 61

The two Ig units composing secretory IgA are held together by what?

Answer 61

the J-chain through disulfide bridges

Question 62

Most IgA is synthesized locally by what?

Answer 62

plasma cells in mammary and salivary glands, and along the respiratory, GI and GU tracts

Question 63

IgA exists as a 170 kDa, four polypeptide chain protein where?

Answer 63

in the serum

Question 64

What is the first Ab produced by a B cell?

Answer 64

IgM

Question 65

Initially, IgM acts as what?

Answer 65

a BCR for B cells

Question 66

IgM is big molecule (900kDa) and therefore found primarily where?

Answer 66

in the bloodstream

Question 67

IgM are of particular importance before when?

Answer 67

before sufficient quantities of IgG have been synthesized

Question 68

The overall avidity of an IgM is quite high, making IgM very effective in doing what?

Answer 68

removal of the microbe

Question 69

What is the primary function of IgD?

Answer 69

Ag receptor on B lymphocytes

Question 70

True or Fasle? | B cells can't express both IgM and IgD

Answer 70

false; B cells can express both and both are specific for the same Ag

Question 71

When IgM and IgD expressed on a B cell interact with an Ag for which they are specific, what happens?

Answer 71

Ag is internalized, processed, and presented to helper T cells

Question 72

B cells activated by B cell receptors proliferate and differentiate into ___ ___ thus initiating the development of a humoral immune response

Answer 72

plasma cells

Question 73

IgE is present in the serum at very low levels and plays a significant role in what?

Answer 73

enhancing acute inflammation, protection from infection by worms, and allergic reactions

Question 74

Ab-mediated allergy is predominantly associated with which Ig?

Answer 74

IgE

Question 75

IgE binds to receptors on mast cells which are specific for the __ region of IgE

Answer 75

Fc

Question 76

When Ag is reintroduced to such "sensitized" mast cells, it binds to IgE molecule on the mast cell and triggers what?

Answer 76

release of mediators

Question 77

IgE is an important component of immediate hypersensitivity syndromes such as?

Answer 77

hay fever and asthma

Question 78

In regards to production of monoclonal Ab, splenocytes from an immunized mouse are isolated and fused with myeloma cells to form hybrid cells with the help of what?

Answer 78

polyethylene glycol

Question 79

Myeloma cells have immortalized properties but do not secrete what?

Answer 79

their own Ig