CMB1003/L22 Humoral Specific Immunity I

Question 1

Give another name for antibodies.

Answer 1

Immunoglobulins

Question 2

Describe the basic structure of antibodies. (3)

Answer 2

2 identical heavy chains
2 identical light chains
Joined by non-covalent interactions and disulphide bridges

Question 3

How are antibodies first expressed?

Answer 3

As membrane-bound B cell receptors in developing B cells

Question 4

What terminals are the variable and constant regions of antibodies?

Answer 4

Variable - N-terminal
Constant - C-terminal

Question 5

Where does cleavage occur in an antibody?

Answer 5

Hinge region

Question 6

What does the Fab contain?

Answer 6

Fragment Antigen Binding
Contains antigen-binding region

Question 7

What does the Fc contain?

Answer 7

Fragment crystalizable
Interacts with Fc receptors on cells with C1q

Question 8

What are the main functions of antibodies? (2)

Answer 8

Bind specifically to epitopes of the pathogen/antigen that elicit immune response
Recruit cells and molecules to destroy the pathogen/antigen

Question 9

Describe the binding of antibodies.

Answer 9

Fab region binds to epitopes of pathogen

Question 10

Describe the possible conformations of epitopes. (2)

Answer 10

Linear
Conformational components of Ag.

Question 11

Give 5 functions of an antibody.

Answer 11

Neutralise
Agglutinate
Opsonize
Activate complement
Improve phagocytosis
Antibody-dependent cellular cytotoxicity
Degranulation

Question 12

What is the aim of neutralising antigens/toxins?

Answer 12

Prevent interaction with cell receptors
Prevent uptake of pathogen by target cells

Question 13

What kind of cell neutralises toxins?

Answer 13

Macrophages

Question 14

Why is agglutination useful? (2)

Answer 14

Impedes travel of pathogen
Alerts immune system more effectively

Question 15

Describe how opsonization occurs.

Answer 15

Extracellular proteins binding to mark pathogen for destruction via phagocytosis

Question 16

Describe direct opsonization.

Answer 16

Binding of antibody to constant region (Fc receptors) to phagocyte receptors

Question 17

Describe indirect opsonization.

Answer 17

Increasing complement (C3b) deposition on pathogen and binding to complement receptors (CR1)

Question 18

How does antibody binding activate the classical complement pathway?

Answer 18

Antigen-antibody complex binds C1qrs
Acts on C4 and C2 to generate C3 convertase

Question 19

Describe ADCC (antibody dependent cellular cytotoxicity). (3)

Answer 19

Detection of antibodies by FcR on several cell types induces cell activation (degranulation)
Lyses target cells
Mainly NK cells

Question 20

Descrive degranulation via Fc receptors (FcR). (2)

Answer 20

Degranulation of mast cells
Killing by NK cells and eosinophils (ADCC)

Question 21

How are antibodies produced in the lab? (2)

Answer 21

Fuse an individual B cell with a B cell tumour line
Generate a hybridoma giving an unlimited supply of monoclonal antibody (mAb)

Question 22

How can antibodies be used in the lab? (2)

Answer 22

Flow cytometry
Western blot
Immunofluorescence

Question 23

How is a Western blot performed? (3)

Answer 23

SDS-PAGE
Transfer to nitrocellulose and overlay with antiserum
Detect bound antibody with enzyme-linked anti-IgG

Question 24

What does flow cytometry achieve?

Answer 24

Identify cells based on panels of proteins they express