5.4 B-lymphocytes and humoral immunity

Question 1

Explain the role of B cells in humoral immunity

Question 2

Describe the process of clonal selection

Answer 2

1. Antibody on surface of B cell attaches to antigen
2. Antigen enters the B cell by endocytosis and gets presented on its surface
3. T helper cells bind to these antigens and stimulate the b cells o divide by mitosis to form a cloned identical b cells
4. B cells all produce the antibody specific to the antigen

Question 3

Define monoclonal antibodies

Answer 3

A clone of a specific antibody

Question 4

Explain the role of plasma cells in the primary immune response

Answer 4

-Secrete antibodies into the blood plasma
-Only survive for a few days but rapidly produce antibodies which kill antigens

Question 5

Explain the role of memory cells in the secondary immune response

Answer 5

• Live for longer than plasma cells
• Circulate in the blood and tissue fluid
• When they encounter the antibody they divide rapidly and develop into plasma cells and memory cells
  -The plasma cells produce the antibody needed to destroy the pathogen
  -New memory cells circulate in blood ready for future infection

Question 6

How do memory cells provide long term immunity

Answer 6

On infection again antibodies are produced at a much faster rate. It ensures that a pathogen is destroyed before it can cause any harm

Question 7

Summarise the role of B cells in humoral immunity

Answer 7

1. Surface antigens are taken up by B cell
2. B cell presents antigens on surface
3. Helper T cells attach to antigen and activate B cells
4. B cells divide by mitosis to give a clone of plasma cells
5. Plasma cells secrete the specific antibody for antigen
6. Antibody attaches to antigen on pathogen and destroys them
7. Some B cells develop into memory cells which respond to the same pathogen upon re-infection and divide by mitosis to produce plasma cells that secrete antibodies