5.3 T lymphocytes and Cell-Mediated Immunity

Question 1

What is an antigen?

Answer 1

Any part of an organism or substance that is recognised as non-self (foreign) by the immune system and stimulates an immune response

Question 2

What are antigens usually?

Answer 2

Proteins that are part of the cell-surface membranes or cell walls of invading cells such as microrganisms or abnormal body cells such as cancer cells

Question 3

What does the presence of an antigen trigger?

Answer 3

Production of an antibody as part of the body’s defence systems

Question 4

What is phagocytosis as an immune response?

Answer 4

Non-specific and occur whatever the infection

Question 5

What are the advantages of specific responses?

Answer 5

Although they are slower in action they are specific to the infection and can provide long term immunity

Question 6

What type of blood cell carries out specific immune responses?

Answer 6

Lymphocytes (type of white blood cell)

Question 7

Where are lymphocytes produced?

Answer 7

In the bone marrow by stem cells

Question 8

Why are B lymphocytes (B cells) names in such a way?

Answer 8

They mature in the bone marrow

Question 9

What type of immunity are B lymphocytes associated with?

Answer 9

Humoral immunity

Question 10

Where do T lymphocytes mature?

Answer 10

The thymus gland

Question 11

What type of immunity are T cells involved in?

Answer 11

Cell-mediated immunity

Question 12

In cell mediated immunity, what do lymphocytes respond to?

Answer 12

Organisms own cells that have been infected by non self material for a different species and cells from other organisms of the same species that are genetically different

Question 13

What will cells that are from a different organism have?

Answer 13

Different antigens on their cell surface membranes from the organisms own cells

Question 14

How do T lymphocytes distinguish between invader cells and own cells?

Answer 14

• phagocytes that have engulfed and hydrolysed a pathogen present some of the pathogens antigens on their own cell-surface membranes
• body cells invaded by a virus present some of the viral antigens on their own cell-surface membrane
• transplanted cells from individuals of the same species have different antigens on their cell-surface membrane
• cancer cells are different from normal body cells and present antigens on their cell-surface membranes

Question 15

What are cells that display foreign antigens called?

Answer 15

Antigen-presenting cells because they can present antigens of other cells on their own cell surface membrane

Question 16

What will T lymphocytes respond to?

Answer 16

Antigens present on body cells (rather than within body fluids)

Question 17

What is t lymphocytes responding to antigens present on body cells known as?

Answer 17

Cell-mediated immunity or cellular response

Question 18

What do the receptors on each T cell respond to?

Answer 18

A single antigen

Question 19

(Response of T lymphocytes to infection by a pathogen)

What is the first stage?

Answer 19

Pathogens invade body cells or are taken in by phagocytosis

Question 20

(Response of T lymphocytes to infection by a pathogen) stage 2, what does the phagocyte do?

Answer 20

Places antigens from the pathogen on its cell-surface membrane

Question 21

(Response of T lymphocytes to infection by a pathogen) stage 3, what happens to the now antigen-presenting cell?

Answer 21

The receptors on a specific helper T cell fit exactly on to these antigens

Question 22

(Response of T lymphocytes to infection by a pathogen) stage 4, what does the attachment of the specific helper T cell onto the antigens of the antigen presenting cell cause?

Answer 22

It activates the T cell to divide rapidly by mitosis and form a close of genetically identical cells

Question 23

(Response of T lymphocytes to infection by a pathogen) what do the cloned T cells do?

Answer 23

• they develop into memory cells that enable a rapid response to future infections by the same pathogen
• they stimulate phagocytes to engulf pathogens by phagocytosis
• they stimulate B cells to divide and secrete their antibody
• activate cytotoxic T cells

Question 24

What do cytotoxic T cells do?

Answer 24

They kill abnormal cells and body cells that are infected by pathogens

Question 25

How do cytotoxic T cells kill infected cells

Answer 25

They produce a protein called performing that makes holes in the cell-surface membrane causing the cell membrane to be freely permeable to all substances and the cell dies as a result

Question 26

What type of pathogen are T cells most effective against?

Answer 26

Viruses because viruses replicate inside cells

Question 27

What type of cells do viruses use to replicate?

Answer 27

Living cells

Question 28

What does the sacrifice of body cells prevent?

Answer 28

Viruses multiplying

Question 29

Define antigen

Answer 29

A protein found on the cell surface membrane that triggers an immune response by lymphocytes

Question 30

State two similarities between T cells and B cells

Answer 30

• both are white blood cells
• both have a role in immunity
• produced from stem cells

Question 31

State two differences between T cells and B cells

Answer 31

• T cells mature in the thymus gland
• B cells mature in the bone marrow
• T cells are cell-mediated
• B cells are humoral immunity