Antigen

Question 1

Rank the following from highest to lowest based on antibody sensitivity?

Answer 1

Protein > Polysaccharide&raquo_space;> Lipid
-> Lipid too common
- -> Especially phospholipid bilayer

Question 2

What is the difference between immunogen and antigen?

Answer 2

Immunogen
-> ability to induce immune response

Antigen
-> ability to combine with antibodies / cell surface receptor (e.g. TCR)

Question 3

What are 3 types of microbial antigen?

Answer 3

Bacterial Ag
Viral Ag
Parasitic Ag

Question 4

What is epitope?

Answer 4

The portion of antigen that is recognized & bound by Ab
-> Antigenic determinants
- -> One antigen can have multiple epitope

Question 5

What 5 factors determines immunogenicity?

Answer 5

Foreignness
-> Self - responsive immune cells are removed

Size
-> Bigger > Smaller

Chemical composition
-> Proteins > nucleic acids / polysaccharides / lipids

Structure
-> Primary / secondary / tertiary structure

Physical form
-> Particulate > soluble

Question 6

Which of the 3 APCs requires induction to generate MHC expression?

Answer 6

Macrophage

Question 7

Which of the 3 APCs require induction to deliver co stimulator (e.g. B7)?

Answer 7

Macrophage
B - cell
-> Remember signal 1 for B cell activation
- -> Ag - mIg ( Induction )
- - -> Expression of MHC - 2
- - -> Expression of B7***

Question 8

Does B cell / T cell require binary complex / ternary ( 3 components ) complex?

Answer 8

(B) cell
-> (B)inary complex
- -> mIg + Ag

(T) cell
-> (T)ernary complex
- -> TCR + Ag + MHC

Question 9

Can B cell / T cell bind with soluble antigen?

Answer 9

B cell

Question 10

Does B cell / T cell binding of antigen requires MHC molecules?

Answer 10

T cell requires MHC to display processed antigen

Question 11

Why are T cells epitope mostly linear peptides?

Answer 11

T cells only binds to antigen that has been processed

Question 12

What is a hapten?

Answer 12

Is an antigen instead of an immunogen itself
-> however coupling up with a immunogenic / non - immunogenic substance can become immunogen

(e.g.
Penicillin degrades forms a group that can bind to albumin
-> causes immune response
- -> Penicillin allergy)

Question 13

What is the use of alum (adjuvant)?

Answer 13

Increases the size of antigen
-> Increase chances of phagocytosis

Question 14

What is the use of Freund’s adjuvant?

Answer 14

Increase persistence of antigen
Stimulates inflammatory response
Activates macrophages & DCs

Question 15

What are autoantigens?

Answer 15

Substances that are normally present in the body
-> but are recognized as antigen by the immune system
- -> causing autoimmune disease

Question 16

What are the 2 strength of Ag - Ab interactions?

Answer 16

Affinity
Avidity

Question 17

What is the definition of affinity?

Answer 17

Measure of strength of binding between a single epitope of a single antigen site on an Ab & a single epitope

Question 18

What is the definition of avidity?

Answer 18

measure of strength of binding between a multivalent Ab & Ag

Question 19

What is isoantigen?

Answer 19

Also called alloantigen
-> type of antigen that differs between individuals in a species
- -> such antigen when enters another individual’s body might be recognized as foreign
- - -> E.g. blood type ( A, B, AB, O )

Question 20

What is cross reactivity?

Answer 20

Antibody that can recognize & bind to a different but structurally similar antigen
-> Blood type A & B
- ->Antibodies in human with blood type A recognized a similar antigen to the ones on blood type B