antigens and immunogens

Question 1

what is an immunogen?

Answer 1

used to define an antigen that is recognized by the immune system via binding and stimulates an immune response.

Question 2

true or false: all antigens are immunogenic

Answer 2

false

Question 3

define antigen

Answer 3

any substance that can bind to components of the immune system (antibodies, cells)

Question 4

define immunogen

Answer 4

any substance that can induce an acquired/adaptive immune response (B or T cell response)

Question 5

what is an example of an antigen that lacks immunogenicity?

Answer 5

hapten

Question 6

how can hapten be visible to the immune system and induce an immune response?

Answer 6

by binding to a macromolecule like protein and function as a carrier protein

Question 7

what is an example of a natural hapten?

Answer 7

urushiol in poison ivy

Question 8

what is a monovalent monodeterminant compund?

Answer 8

antigen with one epitope

Question 9

what is a polyvalent monodeterminant?

Answer 9

antigen with one epitope expressed multiple times

Question 10

what is a monovalent polydeterminant?

Answer 10

antigen contains multiple epitopes that appear to be presented just once

Question 11

what is a polyvalent multideterminant?

Answer 11

antigen is large and expressed different epitopes multiple times

Question 12

what are the 5 characteristics of a strong antigen?

Answer 12

1. foreign
2. high molecular weight
3. physicochemically complex
4. stable
5. degradable

Question 13

what is autoimmunity?

Answer 13

rare circumstances in which select self-antigens can be immunogenic

Question 14

what is an example of a physiochemically complex antigen?

Answer 14

insulin

Question 15

why should a strong antigen be physiochemically complex?

Answer 15

the more structurally complex the antigen the more potential diverse antigenic binding sites there are to be recognized by the immune system

Question 16

why did pharmaceutical companies switch from porcine insulin to recombinant insulin?

Answer 16

even though it was conserved across many species lowering its immunogenicity, the prolonged use can become immunogenic

Question 17

why should a strong antigen be stable?

Answer 17

long enough for antigen processing by the phagocytic cells, if too flexible, it makes recognition and binding difficult

Question 18

what is an example of a poor antigen?

Answer 18

flagellin

Question 19

why are antigens that degrade rapidly not good antigens?

Answer 19

, because they can’t be processed efficiently by APCs for presentation to T cells and B cells. However, if the antigen enzymatically degrades poorly or doesn’t degrade at all, the immune system can’t recognize it.

Question 20

when is the use of materials that are non-immunogenic highly desired?

Answer 20

use of inert metals in joint replacement or bone reconstruction

Question 21

what are the 4 major classes of antigen?

Answer 21

1. carbohydrates (polysaccharides)
2. lipids
3. nucleic acids
4. proteins

Question 22

when do carbs display immunogenic properties?

Answer 22

when bound to proteins to form glycoproteins

Question 23

what are examples of carbs as antigens?

Answer 23

when on the surface of RBCs delineating ABO blood types

antibodies

Question 24

what do lipids display immunogennicity?

Answer 24

when conjugated to proteins

Question 25

what are glycolipids associated with?

Answer 25

cellular membranes

Question 26

true or false: DNA in its helical form is usually non-immunogenic in individuals with healthy immune systems

Answer 26

true

Question 27

what is a rare case in which individuals with hyperactive immune systems to self-antigen develop an immune response to DNA?

Answer 27

systemic lupus erythematosus (SLE)

Question 28

which class of antigen is the most immunogenic and why?

Answer 28

proteins because of their large size and complexity are the most immunogenic. As a result, they typically display multiple epitopes allowing for a robust immune response

Question 29

T cells have a T cell receptor (TCR) on its surface that only recognize a specific processed antigen in the form of a linear _______ presented through a specific surface protein (MHC) on APCs

Answer 29

peptide

Question 30

B cells have a B cell receptor (BCR) that recognizes a specific ________

Answer 30

epitope

Question 31

what is the difference between BCR and TCR?

Answer 31

BCRs are structurally much more different and as a result has more diverse properties

Question 32

the BCR is an antibody that is semi-attached to the B cell surface, such that when the B cell is activated via its BCR receptor complex, it allows the BCR to _____ and become a functional secretory antibody

Answer 32

detach

Question 33

true or false: TCRs can normally recognize and bind to free epitopes on proteins, polysaccharides, lipids that are bound to surfaces of cells, microbes or secretory products

Answer 33

false: BCRs

Question 34

what is a similarity between TCR and BCR antigen recognition?

Answer 34

both receptors only recognize one specific epitope

Question 35

define cross-reactivity

Answer 35

cells with their receptors encounter an epitope with structural properties similar to the original epitope, they could potentially bind to it