5.4 B lymphocytes and humoral immunity

Question 1

What are the characteristics of B lymphocytes?

Answer 1

1. mature in bone marrow
2. associated with humoral immunity

Question 2

Why is it called humoral immunity?

Answer 2

Because it involves in antibodies, and antibodies are soluble in blood and tissue fluid of the body.

Question 3

How will B lymphocytes respond to antigens?

Answer 3

Each B lymphocyte starts to produce a specific antibody that responds to one specific antigen.

Question 4

What is clonal selection?

Answer 4

1. antigens enter B lymphocytes by endocytosis and gets presented on its surface
2. helper T cells bind to these processed antigens and stimulate this B lymphocyte to divide by mitosis to form a clone of identical B lymphocyte
3. all of these clones of B lymphocytes produce the antibody that is specific to the antigen

Question 5

What is endocytosis?

Answer 5

The inward transport of large molecules through the cell-surface membrane.

Question 6

What are the 2 types of cells that a B lymphocyte can divide to form?

Answer 6

1. plasma cells
2. memory cells

Question 7

What are the characteristics of plasma cells?

Answer 7

1. secretes antibodies usually into blood plasma
2. survives for a few days only
3. each cell can produce about 2000 antibodies every second
4. responsible for the immediate defence of the body against infection (primary immune response)

Question 8

What are the characteristics of memory cells?

Answer 8

1. doesn’t produce antibodies directly but circulates in blood and tissue fluid
2. when the body is re-infected by the same pathogen, they divide rapidly and develop into plasma cells and more memory cells
3. lives longer than plasma cells
4. ensures that a new infection is destroyed before it can cause any harm (secondary immune response)

Question 9

What are the stages of responses of B lymphocytes?

Answer 9

1. the antigens of a pathogen are taken up by a B lymphocyte
2. the B lymphocyte processes the antigens and presents them on its surface
3. helper T cells attach to the processed antigens on the B lymphocyte and activate the B lymphocyte
4. the activated B lymphocyte divides by mitosis to give a clone of plasma cells
5. the cloned plasma cells produce and secrete the specific antibody that exactly fits the antigen on the pathogen’s surface (primary immune response)
6. the antibodies attach to antigens on the pathogen and destroy them (primary immune response)
7. some B lymphocytes develop into memory cells
8. these memory cells can respond to future infections by the same pathogen by dividing rapidly and developing into plasma cells that produces antibodies (secondary immune response)