[Unit 5.4] | B-Lymphocytes & Humoral Immunity

Question 1

Describe the process of humoral immunity.

Answer 1

1. Surface antigens of an invading pathogen are taken up by a B cell.
2. The processed antigen is presented on the B cell’s surface.
3. Helper T cells attach to the B cell’s processed antigen and thereby activate the cell.
4. The B cell rapidly divides to clone the plasma cells.
5. The cloned plasma cells produce antibodies specific to the antigens on the pathogen’s surface.
6. The antibodies attach to and destroy pathogens. (PRIMARY RESPONSE)
7. Some B cells develop into memory cells, which can rapidly divide & form plasma cells to fight future infections. (SECONDARY RESPONSE)

Question 2

What is clonal selection?

Answer 2

When a B cell with receptors complementary to an antigen binds to it & gets activated.

Question 3

What is clonal expansion?

Answer 3

When a B cell divides by mitosis to produce lots of cells with receptors specific to an invading pathogen’s antigens.

Question 4

Why is the secondary response much faster than the primary response?

Answer 4

• Much less time is wasted on clonal selection & expansion due to the existence of memory cells.

• The pathogen can be destroyed before it multiplies and causes damage.