Biology__Topic 6__T6L7

Question 1

What are lymphocytes?

Answer 1

white blood cells that help to defend the body against specific diseases. They circulate in the blood and lymph

Question 2

What are lymph nodes?

Answer 2

Filter interstitial fluid. Swollen glands mean you are fighting an infection. They contain lymphocyte reserves

Question 3

What are the different types of lymphocyte?

Answer 3

B cells and T cells

Question 4

What do lymphocytes respond to?

Answer 4

Antigens (proteins and other chemicals that are ‘foreign’) not normally found in the body.

Question 5

What is the response by lymphocytes called?

Answer 5

specific immune response

Question 6

Where are B lymphocytes produced?

Answer 6

bone marrow

Question 7

When are B lymphocyte cells activated?

Answer 7

(Each B cell has one specific type of antigen receptor on its surface.) When its receptor binds to an antigen with the complementary shape.

Question 8

How do B lymphocytes behave when activated?

Answer 8

Secrete antibodies Which bind to antigens on the microbe cell surface membrane. Which act as labels, allowing phagocytes to recognise and destroy the cell

Question 9

What are antibodies?

Answer 9

Special protein molecules called immunoglobulins

Question 10

Why are B cells special

Answer 10

Each B cell binds to only one specific antigen

Question 11

Where are T lymphocytes produced?

Answer 11

bone marrow

Question 12

Where do T lymphocytes mature?

Answer 12

thymus gland

Question 13

Describe T cells

Answer 13

T cells have one specific type of antigen receptor on their surface. This only binds to an antigen with the complementary shape.

Question 14

What are the two types of T cells?

Answer 14

T helper cells and T killer cells

Question 15

What are T helper cells?

Answer 15

When activated, they release cytokines, stimulating the B cells to divide and become cells capable of producing antibodies. They also enhance the activity of phagocytes.

Question 16

What are T killer cells?

Answer 16

Destroy any cells with antigens on their surface membrane that are recognised as foreign or ‘non-self
This includes tissues received as a transplant from another person, and cells infected with pathogens.

Question 17

How are T-helper cells activated?

Answer 17

Macrophage engulfs bacterium with antigens on surface

Macrophage become Antigen Presenting Cell (APC)

APC bind to T cells that have complementary CD4 receptors on their surface

T helper cell divides to produce a clone of active T helper cells and T memory cells.

Question 18

What do antigens on the surface of an APC act as?

Answer 18

Signal to immune system that foreign antigens are present

Question 19

Describe the cloning of B cells

Answer 19

Receptors on B cells bind to complementary foreign antigens and become APCs.
Antigen presenting B cells bind to active cloned T helper cells presenting the same antigen.
T helper cells then release cytokines, stimulating division and differentiation of B cells

Question 20

How do B cells react to cytokines?

Answer 20

Cytokines stimulate the division and differentiation of B cells.

B cells divide to produce two clones of cells: B effector cells and B memory cells

(B effector cells differentiate to produce plasma cells which release antibodies to blood and lymph)

(B memory cells remain in blood for months or years, enabling secondary immune response)

Question 21

What is the process of B cell division called?

Answer 21

clonal selection

Question 22

What do B cells divide to produce under the influence of cytokines?

Answer 22

B effector cells - differentiate to produce plasma cells which release antibodies into blood and lymph. Only live a few days

B memory cells - like T memory cells but longer lived - stay in blood for months/years.

Question 23

What’s the process of B cell division called? Explain a bit

Answer 23

Clonal selection

The first time a B cell comes across a non self antigen complementary to its cell surface receptors, the primary immune response occurs: where “antibody-producing cell” cell production takes 10-17 days.

During this time, the person is most likely to suffer the symptoms of the infection.

Question 24

What’s the role of the T killer cells
(How do they destroy cells)

Answer 24

When host cell is infected with bacterium, it may present the antigen on its surface and become an APC.

T killer cell with complementary receptor binds to APC

T killer cells are stimulated by cytokines (from T helper cells) and divide, forming an active clone

T killer cells release enzymes which create pores in membranes of the infected cells.

Water flows into infected cell, which undergoes lysis

Question 25

What’s the secondary immune response?

Answer 25

If infected by same bacterium/virus, the immune system responds faster

B memory cells produced in primary response immediately differentiate into plasma cells and release antibodies.

Antibody production is greater and response lasts longer

Person often has no symptoms

This person is immune

Question 26

How do cells in the body know that each other aren’t invading pathogens?

Answer 26

There are specific membrane proteins on cell surface

There are hundreds of alleles for these proteins

So the combination of proteins on the cell surface is unique to an individual.

Question 27

How come B and T cells never have antigen receptors that are complementary to body cell surface membrane proteins?

Answer 27

They are destroyed by apoptosis (programmed cell death)

Question 28

What are some examples of the body attacking itself? (AUTOIMMUNE DISEASES)

Answer 28

insulin dependant diabetes
Rheumatoid arthritis
Multiple sclerosis

Question 29

Diagram for antibody

Answer 29

Learn!