Lecture 46: Humoral Immune System

Question 1

Describe the structure of a B-Cell Receptor

Answer 1

• 2 Heavy Chains
• 2 Light Chains
• Disulfide bridge between two heavy chains
• Antigen binding site at tips of ‘Y’
• Variable + Constant regions

Question 2

Different _____ for different B-Cells. Antigens don’t need to be ______ / a peptide to be recognised.

Answer 2

• Antigens

- Processed (in a membrane)

Question 3

B Cells (and T _____) are unique. Most B cells ( or _ Cells) express a different receptor. IgM and IgD are the predominant classes of ______ expressed on ___ B Cells. BCR IgM is present as a monomer, secreted IgM is a pentameter.

Answer 3

• Cells
• T
• Antibodies
• Naive

Question 4

During a parasite infection, you’d want a lot of ___ around.

Answer 4

• IgE

Question 5

Constant regions on the antibody are able to be _____.

Answer 5

• Switched

Question 6

B Cells undergoing class switching maintaining their ____ _____.

Answer 6

• Antigen Specificity

Question 7

Class / Isotype switching:

Answer 7

• IgM / IgD –> IgG –> IgA –> IgE
• Has to go in this direction
• Can’t go backwards because you’re looping out genes that have been tossed out and degraded
• Some steps can be skipped

Question 8

Clonal Selection:

Answer 8

• Selective expansion of unique B Cell Clones that interact with antigen
• Selective specificity
• Antigen specific B Cells then process and display (using MHC-II) to helper T Cells
• Helper T cells squirt out cytokines on to B Cells

Question 9

B Cells that recognise _____ during an immune response are stimulated to undergo ___ ______.

Answer 9

• Antigen

- Cell Division

Question 10

What is the difference between memory B Cells and Clone Plasma Cells?

Answer 10

• Antibody used as receptor on memory B Cells

Question 11

Memory responses:

Answer 11

• Stimulation of B cells by antigen + T cell and lymphatic tissue
• Express antibody as BCR, but do not secrete antibody
• Respond rapidly to antigen encounter and become plasma cells

Question 12

Primary Immune Responses:

Answer 12

• Takes about 7-14 days before sufficient antibody is produced to eliminate pathogen
• Relatively low amount of antibody produced - mainly IgM (pentameric form)
• Very good at activating complement

Question 13

Secondary Immune Responses:

Answer 13

• Basis of the success of vaccination
• Relies on memory B cells
• Fast: 2-3 days, sufficient antibody is produced to eliminate pathogen - mainly IgG