5.3- T LYMPHOCYTES AND CELL-MEDIATED IMMUNITY

Question 1

What type of response is the initial response of the body to infection?

Answer 1

non-specific

Question 2

What is the next phase after the non-specific response?

Answer 2

primary immune response that confers to immunity

Question 3

What is immunity?

Answer 3

ability of organisms to resist infection by protecting against disease-causing microorganisms or their toxins that invade their bodies

Question 4

What does immunity involved? (hint- recognition)

Answer 4

recognition of foreign material (antigens)

Question 5

What is an antigen?

Answer 5

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

Question 6

What are antigens usually?

Answer 6

proteins that are part of cell-surface membranes or cell walls of invading cells, i.e. microorganisms, or abnormal body cells, such as cancer cells

Question 7

What does the presence of an antigen trigger?

Answer 7

production of antibody as part of body’s defence system

Question 8

What type of immune response is phagocytosis?

Answer 8

non-specific

Question 9

When do non-specific immune responses occur?

Answer 9

occur whatever the infection

Question 10

What do specific responses do?

Answer 10

react to specific antigens

Question 11

How fast is the specific response at first?

Answer 11

slower in action first

Question 12

Although specific responses are slower in action, what can they provide?

Answer 12

long-term immunity

Question 13

What type of white blood cell does the specific immune response depend on?

Answer 13

lymphocyte

Question 14

What are lymphocytes produced by?

Answer 14

stem cells in the bone marrow

Question 15

What are the two types of lymphocytes?

Answer 15

B lymphocytes (B cells)

T lymphocytes (T cells)

Question 16

Why are B lymphocytes called B lymphocytes?

Answer 16

they mature in the bone marrow

Question 17

What are B lymphocytes associated with?

Answer 17

humoral immunity, that is immunity involving antibodies that are present in body fluids, or ‘humour’ such as blood plasma

Question 18

Why are T lymphocytes called T lymphocytes?

Answer 18

they mature in the thymus glands

Question 19

What are T lymphocytes associated with?

Answer 19

associated with cell-mediated immunity, that is immunity involving body cells

Question 20

What do lymphocytes respond to? (2)

Answer 20

organism’s own cells that have been infected by non-self materials from a different species, i.e. a virus

cells from other individuals of same species as they’re genetically different

Question 21

What do cells from other individuals have on their cell-surface membrane? (cell-mediated immunity)

Answer 21

different antigens on their cell-surface membrane from the antigens on the organism’s own cells

Question 22

How can T lymphocytes distinguish the invader cells from normal cells: what do phagocytes that have engulfed + hydrolysed a pathogen do?

Answer 22

present some of a pathogen’s antigens on its own cell-surface membrane

Question 23

How can T lymphocytes distinguish the invader cells from normal cells: what do body cells invaded by a virus do?

Answer 23

present some of the viral antigens on their own cell-surface membrane

Question 24

How can T lymphocytes distinguish the invader cells from normal cells: what do transplanted cells from individuals of same species have?

Answer 24

different antigens on their cell-surface membrane

Question 25

How can T lymphocytes distinguish the invader cells from normal cells: what do cancer cells do?

Answer 25

cancer cells are different from normal body cells + present antigens on their cell-surface membrane

Question 26

What are cells that display foreign antigens on their surface called?

Answer 26

antigen-presenting cells

Question 27

Why are cells that display foreign antigens on their surface called antigen-presenting cells?

Answer 27

as they can present antigens of other cells on their own cell-surface membrane

Question 28

What do T lymphocytes respond to only?

Answer 28

antigens that are presented on a body cell

Question 29

What is the T lymphocyte response called? (hint- immunity)

Answer 29

cell-mediated immunity or cellular response

Question 30

Why is the role of the receptors on T cells important?

Answer 30

receptors on each T cell respond to a single antigen

Question 31

As receptors on each T cell respond to a single antigen, what follows?

Answer 31

there's a vast number of different types of T cell, each one responding to a different antigen

Question 32

Stage 1 in response of T lymphocytes to infection by pathogen: what do pathogens do?

Answer 32

pathogens invade body cells or are taken in by phagocytes

Question 33

Stage 2 in response of T lymphocytes to infection by pathogen: what do phagocytes do to the antigens?

Answer 33

phagocytes places antigens from the pathogen on its cell-surface membrane

Question 34

Stage 3 in response of T lymphocytes to infection by pathogen: what do receptors on a specific helper T cell do?

Answer 34

receptors of specific helper T cell fit exactly onto these antigens

Question 35

Stage 4 in response of T lymphocytes to infection by pathogen: what does the attachment of the receptors on helper T cells to antigens do?

Answer 35

activates T cell to divide rapidly by mitosis + form clone of genetically identical cells

Question 36

Stage 5 in response of T lymphocytes to infection by pathogen: what can the cloned T cells do? (4)

Answer 36

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

Question 37

What do cytotoxic T cells do?

Answer 37

kill abnormal cells and body cells that are infected by pathogens

Question 38

How do cytotoxic T cells kill abnormal cells + body cells that are infected by pathogens?

Answer 38

by producing a protein called perforin that makes holes in the cell-surface membrane

Question 39

What does the holes made by cytotoxic T cells from perforin mean?

Answer 39

cell membrane becomes freely permeable to all substances + cell dies as a result

Question 40

What does the cytotoxic T cells perforin making holes in the cell surface membrane and it becoming freely permeable to all cells and cell dying show?

Answer 40

show vital importance of cell-surface membranes in maintaining integrity of cells and hence their survival

Question 41

What is the action of T cells most effective against and why?

Answer 41

viruses as they replicate inside cells viruses use living cells to replicate, this sacrifice of body cells prevents viruses multiplying and infecting more cells