Lecture 3 - Recognition of antigen by B-cells and antibody

Question 1

What is the main role of B-cells?

Answer 1

To attack invaders outside the cells

Question 2

What is the main role of T-cells?

Answer 2

To attack invaders inside the cells

Question 3

True or False? C and T cells have receptors on their surface that can recognise foreign molecules.

Answer 3

True

Question 4

Name the ways that Antibodies can be expressed. [2]

Answer 4

• B-cell surface

- Secreted from B-cells

Question 5

What are the main functions of Antibodies? [2]

Answer 5

• Bind to foreign antigens

- Mediate effector functions to eliminate/neutralise foreign invaders

Question 6

What are the components of an Antibody? [2]

Answer 6

• Fragment antigen binding (Fab) fragment

- Fragment crystallisable (Fc) fragment

Question 7

What is an Antigen?

Answer 7

Part of a molecule that can be recognised by an antibody.

Question 8

List a few examples of Antigens. [4]

Answer 8

• Proteins
• Carbohydrates
• Lipids
• DNA

Question 9

What are antigen epitopes?

Answer 9

Part of the antigen that are recognised by antibodies

Question 10

True or False. Antigen and Antibody binding is not specific.

Answer 10

False.

Question 11

What is a conformational epitope?

Answer 11

• Formed by protein folding

- May not be a continuous sequence of amino acids

Question 12

What is a linear epitope?

Answer 12

Formed by a continuous sequence of amino acids

Question 13

True or False. The antigen binding site must be complementary to the hypervariable regions of an antibody.

Answer 13

True

Question 14

What are the forces that are involved in antibody binding? [4]

Answer 14

• Hydrogen bonds
• Electrostatic interactions
• Van der Waals forces
• Hydrophobic interactions

Question 15

What is affinity, relating to antibody binding?

Answer 15

The stronger the binding between the antibody and antigen mean a higher affinity

Question 16

What is avidity?

Answer 16

• When an antibody used both binding sites to bind to 2 epitopes.
• This increases the avidity (binding strength)

Question 17

When are antibodies made?

Answer 17

After an infection has occured

Question 18

What effect do antibodies have on the body? [5]

Answer 18

• Neutralisation of pathogens
• Opsonisation of pathogens
• Complement activation
• Agglutination of pathogens
• Antibody dependent cell mediated cytotoxicity (ADCC)

Question 19

What happens when antibodies neutralise a pathogen?

Answer 19

The antibodies prevent the pathogen from binding to its target

Question 20

What happens during opsonisation of a pathogen?

Answer 20

The pathogen gets tagged by antibodies and is phagocytosed

Question 21

What happens during complement activation by antibodies?

Answer 21

Antibodies attached to the surface of the pathogen activate the complement system

Question 22

What happens during antibody dependent cytotoxicity (ADCC)?

Answer 22

• Cells (NK cell or macrophages) with FcR bind to antibodies

- Mediated extracellular killing

Question 23

What are applications for immunotherapy?

Answer 23

Use the immune system to attack tumours

Question 24

What is different between each antibody class?

Answer 24

The Fc region

Question 25

What are the five antibody classes? [5]

Answer 25

• IgG
• IgM
• IgD
• IgA1
• IgE

Question 26

What structure does the IgM class form?

Answer 26

• Pentermeric

- Contains a J chain

Question 27

What structure does the IgA class form?

Answer 27

• Dimeric

- Contains a J chain

Question 28

Where are B cells made?

Answer 28

Bone marrow

Question 29

Where is another major site of B cell activity?

Answer 29

Muscosal Associated Lymphoid Tissue (MALT)

Question 30

How does IgA get into the gut?

Answer 30

• Binds to poly-Ig receptor
• Internalised into the cell
• poly-Ig recptor is cleaved
• IgA + secretory component is released at apical side of cell