Antigens - Midterm

Question 1

Antigen made by the intracellular pathogen inside a host cell (host cell is infected with the pathogen)

Answer 1

• endogenous antigen

Question 2

Replicate outside of host cell

Answer 2

• extracellular pathogens

Question 3

Do not recognize and only display. Do not bind epitope. They bind the antigen and present epitope.

Answer 3

• MHC

Question 4

Small antigenic molecules that are too small to be immunogenic (no Ab production) unless it is bound to a carrier protein (a larger molecule that can be seen by the immune system)

Answer 4

• haptens

Question 5

All viruses and some bacteria and parasites

Answer 5

• intracellular pathogens

Question 6

A horse with Type A blood has a transfusion with Type B blood and shows no reaction. Was this the first time the horse had a transfusion? Why no response?

Answer 6

• yes it was the first time
• because dogs and horses do not generate natural antibodies against RBC antigens
• > therefore, no response the first time
• > BUT the second time it could be fatal!!!

Question 7

Can be conformational or linear. May involve elements of primary, secondary, tertiary or quaternary.

Answer 7

• protein epitopes

Question 8

The portion of the antigen molecule that actually binds with antibodies, TCR, or BCR

Answer 8

• the epitope

- > the piece of antigen recognized by a cell

Question 9

Allergens, Self molecules and molecules from another animal

Answer 9

• non-microbial molecules

Question 10

What size is a good immunogen?

Answer 10

• over 1000 daltons ( > 1kDA) to be immunogenic

Question 11

Which species do and do not generate natural antibodies against RBC antigens?

Answer 11

• DO NOT: Dogs and Horses
• > in species that don’t, need to be aware the second time a transfusion is performed
• DO: Humans, Cats, Pigs
• > in species that do, need to be aware of this the first time we do a transfusion

Question 12

When can T-cells see and bind antigens?

Answer 12

• when an MHC molecule presents it

Question 13

Are all antigens immunogenic?

Answer 13

• Not all antigens are immunogenic, but all immunogens are antigenic
• > AKA some foreign molecules can bind product of an acquired immune response, BUT can NOT stimulate an immune response

Question 14

MHC displays epitopes to?

Answer 14

• TCR

Question 15

Drives adaptive Immune response

Answer 15

• antigens

Question 16

Expressed on a subset of T-lymphocytes that “kill” abnormal cells

Answer 16

• CD 8 +T Cell, or CTL (Cytotoxic T Cell)

Question 17

Surface molecules (antigens) on immune cells

Answer 17

• non-microbial antigens

- > Cluster of Differentiation(CD) molecules

Question 18

Molecules expressed on the surface of normal cells

Answer 18

• cell surface antigens

Question 19

Protein molecules expressed on the surface of cells that have nuclei

Answer 19

• Major Histocompatability Complex Molecules (MHC)

- > non-microbial antigens

Question 20

Ability of an antigen to bind with immune components

Answer 20

• antigenicity

Question 21

Important in recognition and signaling for generating an adaptive immune response. Important for tissue recognition (transplantation medicine)

Answer 21

• MHC molecules

Question 22

Can target the virus while outside of the cell

Answer 22

• antibodies

Question 23

FcR and Complement proteins bind Fc region with a much higher affinity if?

Answer 23

• the Antibodies Fab region has bound its antigen

- > prevents phagocytosis of free unbound antigen and homeostatic complement activation

Question 24

Reactions to the wrong blood type are most likely due to?

Answer 24

• cross reacting antibodies

- > because blood types have glycoproteins AND bacteria have glycoproteins on their cell wall

Question 25

Molecules that can be induced to be expressed on nucleated cells

Answer 25

- MHC-1

Question 26

Antibodies against foreign antigens without any known previous infection, vaccination, other foreign antigen exposure or immunization to account for it

Answer 26

- natural antibodies | - > probably a result from a cross-reaction to antibodies made to harmless bacteria or food antigens

Question 27

A molecule capable, under appropriate conditions, of inducing a specific immune response.

Answer 27

- antigen | - > foreign molecular structure

Question 28

Amino acids are separated, but brought together by folding.

Answer 28

- conformational epitope

Question 29

What are good complex immunogens?

Answer 29

- proteins and glycoproteins

Question 30

Binds to IL-2

Answer 30

- CD 25 = Interleukin-2 Receptor = IL-2R

Question 31

If the antigen is killed in a phagosome it is likely?

Answer 31

- exogenous antigen - > exception is Mycobacterium bovis because if a phagocytic cell engulfs it it can replicate inside and is not killed and is therefore an endogenous antigen

Question 32

Molecules that are only expressed on Antigen-Presenting Cells (APCs)

Answer 32

- MHC-2

Question 33

Identical or similar epitopes from different sources. Antibodies directed against one antigen may react unexpectedly with an unrelated antigen (but one that has a very similar epitope)

Answer 33

- cross-reactivity of epitopes

Question 34

Antigen made by the pathogen outside any host cell

Answer 34

- exogenous antigens

Question 35

Expressed by a subset of T-lymphocytes that have “helper” function

Answer 35

- CD 4 + T Cell, or T-Helper Cell

Question 36

Most bacteria and parasites, but not all

Answer 36

- extracellular pathogens

Question 37

Antigenic determinant sites and the portion of the antigen which is bound and recognized by antibodies (Ab), TCR and BCR

Answer 37

- epitomes

Question 38

What molecules make the best antigens?

Answer 38

- foreign proteins

Question 39

What binds and presents antigens, but does not recognize them?

Answer 39

- MHC molecules

Question 40

Ability of the antigen to induce immune responses

Answer 40

- immunogenicity

Question 41

When can B-cells see and bind antigens?

Answer 41

- bind antigens that are free in solution via their BCR (B-cell receptor) - > antigen is not presented to it by another cell

Question 42

They infect cells in order to replicate (makes endogenous antigens)

Answer 42

- viruses

Question 43

Example of a hapten

Answer 43

- Penicillin | - > alone too small to elicit immune response, but if bound to carrier protein albumin it will

Question 44

Which immune cells can kill virus-infected cells

Answer 44

- NK and CTLs (cytotoxic T-cells)