Chp 4

Question 1

Immunogen

Answer 1

A stimulus that produces a humoral or cell mediated immune response; activates immune system

Question 2

Antigen

Answer 2

Any substance that binds specifically to an antibody or a T- cell receptor

Question 3

Haptens

Answer 3

Some very small molecules that can bind to antibodies or TCR’s, but they cannot initiate an immune response ; can be made immunogenic by conjugation with a carrier (a larger molecular weight protein)

Question 4

Epitope

Answer 4

The portion of an antigen that is recognized and bound by an antibody or TCR/MHC complex

Question 5

Polyclonal

Answer 5

When multiple antibodies are produced by B cell against one antigen because there are more than one epitopes (antiserum)

Question 6

Monoclonal

Answer 6

Produces one antibody by picking just one antibody

Question 7

Why must antigen be degraded?

Answer 7

The APCs must degrade the antigen to be presented to the TCRs and BCRs

Question 8

Differences between BCR receptor and antibody?

Answer 8

Antibody circulates through blood and lymph while BCRs are embedded in the membrane

Question 9

Variable part of the antibody?

Answer 9

Is the only part interacting with antigen

Question 10

Interaction between antigen and antibody?

Answer 10

Non covalent binding incuding electrostatic interactions, hydrophobic interactions, hydrogen bonding, and van der waals. Since these interactive forces are relatively weak, the fit between antigen and and its complementary site on the antigen receptor must occur over an area large enough to allow the summation of all possible available interactions

Question 11

What are adjuvants?

Answer 11

Molecules that enhance the immune response against the immunogen

Question 12

How do adjuvants work?

Answer 12

• Increasing the biological or immunological half life of vaccine antigens
• Increasing the production of local inflammatory cytokines
• Improving antigen delivery, processing, and presentation by APCs, especially the dendritic cells (TLR receptors)

Question 13

How do adjuvants work?

Answer 13

• Increasing the biological or immunological half life of vaccine antigens
• Increasing the production of local inflammatory cytokines
• Improving antigen delivery, processing, and presentation by APCs, especially the dendritic cells (TLR receptors)

Question 14

What does being immunogenic mean?

Answer 14

An immunogen capable of inducing an immune response

Question 15

All immunogens are antigens, but not all antigens are immunogens

Answer 15

This is because there are many compounds that are incapable of inducing an immune response, yet they are capable of binding with components of the immune system that have been induced specifically against them

Question 16

What are the requirements for immunogenicity?

Answer 16

1. Foreignness
2. High molecular weight
3. Chemical complexity
4. Degradability and interaction with host major histocompatibility complex (MHC) molecules

Question 17

What does foreignness mean?

Answer 17

Animals normally do not respond immunologically to self. If something is injected with its own serum, then the self will recognize it and not make an immune response. But if the serum was from a different animal, there would be an immune response
Ex; rabbit injected with its own serum albumin vs rabbit serum injected into a guinea pig

Question 18

What does high molecular weight mean?

Answer 18

Relatively small substances have decreased immunogenicity while larger substances have increased immunogenicity. The small ones do not activate the receptor with enough force as it should

Question 19

What does chemical complexity mean?

Answer 19

Basically meaning there needs to be a complex set of amino acids within the immunogen to make it immunogenic. A polymer containing just lysine will not be immunogenic. Increase in chemical complexity, increases immunogenicity

Question 20

Can antibodies recognize all structures of proteins?

Answer 20

Yes, primary, secondary, tertiary, and quaternary

Question 21

What does degradability?

Answer 21

APCs must first degrade the antigen through a process known as antigen processing before they can express antigenic epitopes on their surface. Once degraded and noncovalently bound to MHC, these epitopes stimulate the activation and clonal expansion of antigen specific effector T cells

Question 22

What properties must an antigen have to be susceptible to enzymatic degradation?

Answer 22

1. It has to be sufficiently stable so that it can reach the site of interaction with B cells or T cells necessary for immune response
2. The substance must be susceptible to partial enzymatic degradation that takes place during antigen processing by APCs

Question 23

Examples of antigens that can/cannot be degraded?

Answer 23

Peptides composed of D- amino acids are resistant to enzymatic degradation and are therefore not immunogenic whereas their L isomers are susceptible to enzymes and are immunogenic

Question 24

What are some further requirements for immunogenicity?

Answer 24

1. Genetic makeup of the immunized individual
2. Dosages and route of administration of the antigen (not a high enough dosage)
   - antigens delivered subcutaneously generally elicit the strongest immune responses because due to dendritic cells (Langerhans), which uptake, process, and present antigen to effector cell

Question 25

What is primary immunization?

Answer 25

The first exposure of an individual to an immunogen

Question 26

Where in the immunoglobulin does it specifically bind to the epitope or antigenic determinant ?

Answer 26

In concentrated hypervaribale regions known as the complementarity- determining region (CDR)

Question 27

Can T cells bind to soluble antigens?

Answer 27

No

Question 28

What is the difference between B cells binding to an antigen and T cells binding to an antigen?

Answer 28

Membrane bound antibodies that are present on B cells recognize and bind to free antigen in solution. The epitopes of the antigen are generally on the outside of the molecule accessible for interaction with the B cell. Terminal side chains of polysaccharides and hydrophilic portions of protein molecules generally constitute B cell epitopes. In contrast to B cells, T cells are unable to bind to soluble antigen. The interaction of an epitope with the TCR requires APC processing of the antigen in which enzymatic degradation takes place to yield small peptides, which the associated with the MHC.

Question 29

Antigen interaction B cells vs T cells

Answer 29

B cells- BCR binds Ag via epitope | T cell- TCR bings antigenic peptides bond to MHC

Question 30

Nature of antigens B cells vs T cells

Answer 30

B cells- Protein, polysacharride, and lipid | T cells- Peptide

Question 31

Binding soluble antigens B cells vs T cells

Answer 31

B cells- yes | T cells- no

Question 32

Epitopes recognizes B cells vs T cells

Answer 32

B cells- accessible, sequential, or nonsequential | T cells- Internal linear peptides produced by antigen processing

Question 33

What are the major classes of antigens?

Answer 33

1. Carbohydrates 2. Lipids 3. Nucleic Acids 4. Proteins

Question 34

Carbohydrates

Answer 34

Can only be immunogenic when associated with protein carriers. For example, glycoproteins. Another example of antigenicity of polysaccharides is the immune response associated with the ABO blood groups.

Question 35

Lipids

Answer 35

Rarely immunogenic, but an immune response to lipids may be induced if the lipids are conjugated to protein carriers. May be regarded as haptens

Question 36

Nucleic acids

Answer 36

Poor immunogens. Become immunogenic when they are conjugated with protein carriers. DNA usually nonimmunogenic

Question 37

Proteins

Answer 37

Virtually all proteins are immunogenic; most common immune response are to those of proteins

Question 38

Toxoid

Answer 38

A toxin that has been modified to the extent that it is no longer toxic but still remains some of its immunochemical characteristics

Question 39

Cross- reacts

Answer 39

It is possible to immunize individuals with the toxoid and thereby induce immune responses to some of the epitopes that the toxoid still shares with a native toxoid because the epitopes have not been destroyed by the modification---- The toxin and toxoid share enough epitopes to allow the immune response to the toxoid to mount an effective defense against the toxin itself

Question 40

Will a hapten become immunogenic when mixed with an adjuvant?

Answer 40

No, it must be conjugated covalently with a carrier