Antibodies

Question 1

What is an antigen?

Answer 1

Any molecule that can bind specifically than antibody or antigen receptor

Question 2

What is an epitope?

Answer 2

A site on an antigen recognised by an antibody or an antibody receptor

Question 3

What is an antibody?

Answer 3

A protein that binds specifically to a particular structure

Question 4

What is affinity and avidity?

Answer 4

Affinity- binding of one Fab region with one epitope

Avidity- overall attraction/binding between the two molecules

Question 5

What are the 5 main subclasses of Immunoglobulins?

Answer 5

IgM, IgG, IgA, IgE, IgD

Question 6

Where are IgM and IgG and IgD produced?

Answer 6

Spleen and lymph nodes

Question 7

Where are IgA and IgE produced?

Answer 7

Intestinal and respiratory tracts

Question 8

Describe the structure of IgG

Answer 8

2 antigen binding sites, single constant fragment, hinge region with disulphide bond, heavy and light chain

Question 9

Describe the structure of IgM

Answer 9

Forms pentameric structure, 5 subunits joined with glycoprotein bonds

Question 10

Describe the structure of IgA

Answer 10

2 subunits, J chain joining two chains together with a secretory component

Question 11

What is the constant region and variable region of an antibody?

Answer 11

Constant- (Fc) The part of the immunoglobulin that interacts with host therefore alters effector function

Variable- (Fab) variable region dictates the interaction with the pathogen

Question 12

What are the three functions of Fc?

Answer 12

1) Fc binds to FcR which stimulates effector function
2) Fc portion of antibody antigen complexes initiates the complement cascade
3) Fc portion delivers antibody to specific areas by active transport

Question 13

What is class switching?

Answer 13

When an antibody changes is Fc (constant) region such as IgM to IgG but Fab region remains the same

Question 14

What are the key differences between a primary and secondary immune response?

Answer 14

Primary short lived, isolate IgM, memory cells established

Secondary rapid, longer, IgG/IgA

Question 15

How does antigen-antibody binding protect the host?

Answer 15

Neutralise by binding- prevent attachment, invasion of cells, toxin prodction
Bind bacteria to macrophage- opsonisation
Virus/toxin neutralisation
Antibody dependent cell cytotoxicity
Direct antimicrobial activity
Complement activation

Question 16

Name a tissue specific example of an effector?

Answer 16

Mucosal of intestines
Secreted locally by B cells
Picks up polymeric Ig receptor 
Passes into lumen
Receptor proteolyses leaving secretory component to attach and protect mucosa