5.4 B Lymphocytes and humoral immunity

Question 1

What does humoral (body fluids) immunity involve?

Answer 1

Antibodies

Question 2

Where are antibodies soluble?

Answer 2

In the blood and tissue fluid of the body.

Question 3

Define endocytosis

Answer 3

The inward transport of large molecules though the CSM.

Question 4

Explain the process of clonal selection

Answer 4

1. antigen of a pathogen, foreign in cell, toxin, damaged or abnormal cell enters the blood or tissue fluid
2. there will be one B cell that has an antibody on its surface whose shape is complementary. The antibody therefore attaches to the complementary antigen
3. the antigen enters the B cell by endocytosis and gets presented on its surface
4. T cells bind to these processed antigens and stimulate this B cell to divide by mitosis to form a clone of identical B cells (all of which produce antibodies specific to the foreign antigen)

Question 5

Overall, what does clonal selection account for?

Answer 5

The body’s ability to respond rapidly to any of a vast number of antigens.

Question 6

Define monoclonal antibodies

Answer 6

An antibody produced by a single clone of cells

Question 7

In each clone, the cells produced develop into what 2 types of cells?

Answer 7

1. Plasma cells (primary immune response)

2. Memory cells (secondary immune response)

Question 8

What do plasma cells do?

Answer 8

Secrete antibodies usually into the blood plasma. They survive only for a few days but can make approx 2000 antibodies every second during it s brief lifespan.

These lead to the destruction of the antigen.
Plasma cells are therefore responsible for the immediate defence of the body against infection.

Question 9

What do memory cells do?

Answer 9

(memory cells live considerably longer than plasma cells often decades.)

These cells do not produce antibodies directly but circulate in the blood and tissue fluid. When they encounter the same antigen at a later date, they divide rapidly and develop into plasma cells and more memory cells.

The plasma cells produce the antibodies needed to destroy the pathogen, while the new memory cells circulate in readiness for any future infection.

In this way memory cells provide long-term immunity against the original infection. An increase quantity of antibodies is secreted at a faster rate than In the primary response ensuring a new infection is destroyed before it can cause any harm .

Question 10

Define primary immune response

Answer 10

(reaction of the immune system when it contacts an antigen for the first time.)
The production of antibodies and memory cells

Question 11

Define secondary immune response

Answer 11

reaction of the immune system when it contacts an antigen for the second and subsequent times.

Question 12

Explain 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. the B cell processes the antigens and presents them on its surface
3. helper T cells attach to the processed antigens on the B cells thereby activating the B cell
4. the B cell is now activated to divide 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
6. the antibody attaches to antigens on the pathogens and destroys them
7. some B cells develop into memory cells. These can respond to future infections by the same pathogen by dividing rapidly and developing into plasma cells that produce antibodies. (secondary immune response)