Immune System Antigens

Question 1

What is an antigen or immunogen?

Answer 1

Any substance that can induce an immune response (B cell or a T cell immune response)
Antigen drives immune response

Question 2

2 types of Antigen

Answer 2

Infectious
bacterial
viral
protozoal
helminths
Noninfectious
self antigen
food antigen
plant product
dust
cell surface proteins
synthetic chemicals
venoms
insect toxin

Question 3

Antigenicity

Answer 3

ability to induce an immune response

Question 4

Essential feature of antigenicity

Answer 4

Size of antigen
complexity
stability
degradability
foreignness

Question 5

Size of antigen

Answer 5

Large=strong immune response
Small=poor immune response
Very small=no immune response

Question 6

Complexity

Answer 6

Complex antigens are good antigens
proteins are good antigens or immunogens
Simple substances are poor antigens
pure lipids, polymers are not good at inducing immune response

Question 7

Stability

Answer 7

flexible structure are poor antigens (flagellin)
moveable structure are poor antigens
fixed and stable are strong antigen

Question 8

Degradability

Answer 8

highly degradable substances are poor antigen.
non-degradable are also poor antigen
steel pins, plastic heart valve implant-poor

Question 9

Foreignness

Answer 9

The more foreign-farther away on the evolutionary tree, the quicker/strong the antigen
a characteristic feature of the normal immune foreign (non-self) but not to self antigen

Question 10

Antigen-Antibody interaction

Answer 10

Antigen concentration influences immune response or tolerance
antigen concentration affects the induction of an immune response
low antigen concentration-T cells inresponsive-tolerance
moderate antigen concentration-Immune response
excessive antigen concentration-T and B cells are unresponsive-Tolerance

Question 11

Antigen-antibody interaction

Answer 11

antigen-antibody binding is highly specific
any changes in shape or chemical structure of an antigen will prevent binding of antibody to an antigen

Question 12

Epitopes

Answer 12

A single large molecule (protein) can be show to induce multiple immune response
Large molecules have regions against which immune responses are directed
Also called antigenic determinants

Question 13

Hapten

Answer 13

A small molecules (less than 1000 daltons) that by itself cannot induce an immune response.
When bound to proteins it can provoke a strong immune response
small molecule(no immune response)
carrier(immune response)

Question 14

Cross reactive epitopes

Answer 14

common epitope found on diverse antigen

Question 15

Where can cross reactive epitopes occur

Answer 15

two different organisms (brucella and yersenia)
between microbes and mammalian self tissue (molecular mimicry)

Question 16

Key Points of Immune System Antigen

Answer 16

immune response is antigen driven
foreign, large complex, stable and moderately degradable substances tend to be excellent antigens
antigen-antibody interactions are specific
antibodies recognize the shape of an antigen
any minor alterations in the antigenic structure will affect the binding of an antibody to an antigen