5.4 B lymphocytes and Humoral Immunity

Question 1

What does humoral immunity involve?

Answer 1

Antibodies

Question 2

Are antibodies soluble in blood and tissue fluid?

Answer 2

Yes

Question 3

What does ‘humour’ refer to?

Answer 3

Bodily fluids

Question 4

What does each B cell produce?

Answer 4

A specific antibody that responds to one specific antigen

Question 5

Examples of antigens

Answer 5

Proteins on the surface of a pathogen, foreign cell, toxin, damaged or abnormal cell

Question 6

What happens when an antigen on a pathogen/abnormal cell enters the blood or tissue fluid?

Answer 6

There will be one B cell that has an antibody on its surface whose shape exactly fits the antigen (they are complimentary) the antibody attaches to the complimentary antigen. The antigen enterenters the B cell by endocytosis and gets presented on its surface. T helper cells bind to the processed antigens and stimulate the B cell to divide by mitosis to form a clone of identical B cells all of which produce the antibody that is specific to the foreign antigen
-clonal selection

Question 7

Why are the clones that B cells create known as monoclonal?

Answer 7

Each clone produces one specific antibody

Question 8

In each clone produced by B cells what two ways can the cells develop?

Answer 8

Into plasma cells or memory cella

Question 9

What do plasma cells do?

Answer 9

• Secrete antibodies usually into blood plasma
• Can survive for a few days
• Antibodies it produces lead to the destruction of the antigen

Question 10

What do memory cells do?

Answer 10

• Second immune response
• Can live for decades
• Do not produce antibodies directly
• Circulate in the blood and tissue fluid
• When they encounter the same antigen again then divide rapidly and develop into plasma cells and more memory cells, the plasma cells will secrete the antibodies and the memory cells will circulate the humoral for future infection
• Provide long term immunity

Question 11

What happens as a result of memory cells?

Answer 11

Immune response faster than primary response and ensures that new infection is destroyed before it can cause harm, often individuals will be unaware that they are infected

Question 12

Give a summary of the role of B cells in humoral immunity

Answer 12

1. Surface antigens of an invading pathogen are taken up by a B cell
2. B cell processes antigens and presents them on its surface
3. Helper T cells attach to the processed antigens on the B cell activating the B cell
4. B cell divides by mitosis to give clones of plasma cells
5. the cloned plasma cells produce and secrete the specific antibody that fits the antigen on the pathogens surface
6. Antibody attaches to antigens on the pathogen and destroys them
7. Some B cells develop into memory cells which circulate in the humoral and are capable of responding to future infections by the same pathogen by dividing rapidly into the plasma cells that produce antibodies