WEEK 10: 10.4 The Adaptive Immune System: Humoral & Cell-Mediated Immunity

Question 1

Can CD4 and CD8 T cells recognise protein antigens in their natural form?

Answer 1

No

Question 2

What kind of antigens can CD4 and CD8 T cells recognise via their TCR

Answer 2

processed, presented antigens (peptides)

Question 3

Describe 2 steps in antigen processing

Answer 3

1. antigen presents in its natural form
2. antigen is chopped up/processed into shorter peptides

Question 4

Describe 2 steps in antigen presentation

Answer 4

1. Processed antigen is presented on MHC molecule
2. TCR on T cells recognise processed antigen on MHC

Question 5

CD8 T cells recognise processed peptides presented on?

Answer 5

MHC class 1

Question 6

CD4 T cells recognise processed peptides presented on?

Answer 6

MHC class 2

Question 7

MHC class 1 presents

Answer 7

endogenous peptides

Question 8

MHC class 2 presents

Answer 8

exogenous peptides

Question 9

Describe the antigen processing of MHC class 1 in 6 steps

Answer 9

1. endogenous protein is synthesised in body
2. protein digested into short peptides
3. peptides enter endoplasmic reticulum
4. peptides loaded onto MHC class 1 molecules
5. MHC class 1 is exported to the surface via vesicular transport
6. MHC class 1 is expressed on a nucleated cell

Question 10

Describe the antigen processing of MHC class 2 in 5 steps

Answer 10

1. exogenous antigens are taken up via pinocytosis, endocytosis or phagocytosis
2. exogenous antigen is digested in the endosome by lysosome digestive enzymes
3. MHC class 2 travels from endoplasmic reticulum into the endosome
4. peptide is loaded onto MHC class 2 molecule
5. MHC class 2 expressed on antigen presenting cell

Question 11

Describe the internal MHC class

Answer 11

When dealing with intracellular pathogens/tumors, the cell induces apoptosis of the infected cell; activation of CD8 T cells via MHC class 1 presentation leads to the production of effector cytotoxic T cell

Question 12

Describe the external MHC class

Answer 12

extracellular pathogens involve the antibody and phagocytosis; activation of CD4 T cells via MHC class 2 presentation enables the production of helper T cell.

Question 13

Define the term immunoglobin

Answer 13

Refers to the structure of a molecule (eg. an Ig molecule is made up of light and heavy chains)

Question 14

define the term antibody

Answer 14

Refers to the function of a molecule (eg. following my vaccination I now have antibodies to influenza)

Question 15

Describe immunoglobin structure

Answer 15

they are Y shaped glycoproteins, made up of 4 polypeptides joined by 4 disulfide bonds

Question 16

Describe the function of immunoglobins

Answer 16

they bind to antigen at antigen binding site; the base of the molecule mediates biological activity

Question 17

Identify the 5 different isotypes of immunoglobin, their structure, no of binding sites and binding location

Answer 17

IgM - pentameric, 10, blood/tissue
IgA - dimeric, 4, mucosa
IgD - monomeric, 2, blood/tissue
IgG - monomeric, 2, Blood/tissue
IgE - monomeric, 2, mucosa/GI/resp tract

Question 18

Where are immunoglobins produced and by what?

Answer 18

They are produced by B cells in the bone marrow

Question 19

what are immunoglobins expressed on the surface of B cells called?

Answer 19

B cell receptor (BCR)

Question 20

Define antigen

Answer 20

A substance that is capable of stimulating an immune response in the body, typically a protein/carbohydrate

Question 21

Define antibody

Answer 21

Substances produced by the immune system in response to the presence of antigens