3.6-specific cellular defences against pathogens

Question 1

how is the specific immune response brought about?

Answer 1

specific immune response brought about by lymphocytes coming from stem cells in the bone marrow

Question 2

what happens to some lymphocytes?

Answer 2

some lymphocytes pass to the thymus (a gland)

they then develop into T lymphocytes

Question 3

what happens to the lymphocytes that don’t pass to the thymus?

Answer 3

lymphocytes that don’t pass to the thymus remain and mature in the bone marrow

become B lymphocytes

Question 4

what are lymphocytes?

Answer 4

white blood cells involved in the specific immune response

Question 5

what do lymphocytes respond to?

Answer 5

lymphocytes respond to specific antigens on invading pathogens

Question 6

what classifies something as an antigen?

Answer 6

an antigen is classified by any foreign molecule that causes a specific immune response from a lymphocyte

Question 7

5 things that can act as antigens

Answer 7

viruses

bacteria

bacterial toxins

molecules on the surfaces of transplanted cells

cancer cells

Question 8

what are antigens?

Answer 8

molecules, often proteins, located on the surface of cells that trigger a specific immune response

Question 9

2 steps of clonal populations

Answer 9

each lymphocyte has a single type of membrane receptor which is specific for one antigen and can only be activated by this one antigen

when a lymphocyte is attached to an antigen, the lymphocyte responds by dividing repeatedly to form a clonal population of identical lymphocytes

Question 10

what does an antigens presence trigger?

Answer 10

an antigens presence triggers production of antibodies by B lymphocytes

Question 11

what shape is an antibody?

Answer 11

Y-shaped

Question 12

what does each of an antibody’s arms bear?

Answer 12

a receptor binding site specific to a particular antigen on a pathogen

Question 13

2 outcomes when a B lymphocyte responds to its specific foreign antigen

Answer 13

multiply to form a clone of activated B cells which make antibodies for immediate use

multiply to form a clone of memory B cells capable of making antibodies in the future if required

Question 14

when are clones of activated B cells and memory B cells formed?

Answer 14

when a B lymphocyte responds to its specific foreign antigen by multiplying to form them

Question 15

how are antibodies released and what do they do?

Answer 15

antibodies released from the blood and lymph systems are transported around the body

make their way to infected area

Question 16

what happens once antibodies arrive at the infected area?

Answer 16

recognise and combine with antigens

Question 17

what inactivates pathogens and how?

Answer 17

pathogens are inactivated by the formation of an antigen-antibody complex

makes pathogen susceptible to phagocytosis

Question 18

4 harmless substances B lymphocytes may over-react to

Answer 18

pollen

dust

feathers

penicillin

Question 19

what is an allergic reaction?

Answer 19

hypersensitivity in the form of an exaggerated immune response

Question 20

what does a phagocyte do after destroying a pathogen?

Answer 20

after a phagocyte destroys a pathogen, it presents fragments of the pathogen’s antigen at its surface

Question 21

what do T lymphocytes do and how?

Answer 21

T lymphocytes destroy infected body cells

recognise antigens of the pathogen on the cell membrane

Question 22

3 steps in T lymphocytes destroying infected body cells

Answer 22

attach onto body cells and release proteins

proteins diffuse into cells causing production of self-destructive enzymes which causes cell death (apoptosis)

T lymphocyte disengages from cell and process repeats on other infected cells

Question 23

what is apoptosis?

Answer 23

programmed cell death

Question 24

what is not destroyed by apoptosis?

Answer 24

infected cell’s membrane

Question 25

what happens when an infected cell’s membrane isn’t destroyed?

Answer 25

cell contents and pathogenic antigens remain enclosed

then engulfed and digested by a phagocyte

Question 26

how do lymphocytes usually avoid attacking body cell surface proteins thinking their antigens?

Answer 26

lymphocytes with an antigen receptor that fits a body cell surface protein is classed as non-functional or destroyed by apoptosis

Question 27

what can T lymphocytes distinguish between?

Answer 27

self-antigens on the surface of the body’s own cells
(therefore take no action)

non self-antigens on the surfaces of infected cells or cells not belonging to the body
(therefore initiate immune response)

Question 28

what does the ability to distinguish between self and non-self mean?

Answer 28

lymphocytes normally don’t work against self body cells surface proteins

Question 29

what makes T lymphocytes respond to self antigens and what happens?

Answer 29

T lymphocytes respond to self antigens due to failure of the regulation of the immune system

T lymphocytes attack the body’s own cells

Question 30

what is it called when T lymphocytes attack the body’s own cells?

Answer 30

autoimmunity

Question 31

2 diseases autoimmunity can cause

Answer 31

type 1 diabetes

rheumatoid arthritis

Question 32

when does the body produce antibodies and what is this called?

Answer 32

when a person is infected by a disease-causing organism

primary response

Question 33

what does the primary response often not do?

Answer 33

prevent the person from becoming ill

Question 34

what is the secondary response and how does it work?

Answer 34

when a person is exposed to the same antigen at a later date

memory cells rapidly give rise to anew clone of specific lymphocytes

lymphocytes destroy invading pathogens before individual shows symptoms

Question 35

3 reasons the disease is usually prevented in the secondary response

Answer 35

antibody production is much more rapid

concentration of antibodies produced reaches a higher level

higher concentration of antibodies is maintained for a longer time

Question 36

how is antibody production different in the secondary response compared to the primary?

Answer 36

production is greater and more rapid

Question 37

what are memory cells?

Answer 37

memory cells are B and T lymphocytes specific to the antigen and produced in response to it

Question 38

2 things memory cells produce when a disease-causing microorganism reappears

Answer 38

clones of T cells

antibody forming B cells

Question 39

what does an immunodeficiency disease result from and what does it affect?

Answer 39

the absence or failure of some component of the immune system

leaves the person susceptible to infection

Question 40

what is AIDS and how is it caused?

Answer 40

acquired immunodeficiency syndrome is a deficiency disease

caused by HIV (human immunodeficiency virus)

Question 41

what does HIV attack and how?

Answer 41

T lymphocytes

attaches to specific receptors on T cell’s surface

coat surrounding HIV particle fuses with the membrane of the T cell and the virus enters and destroys the cell

Question 42

what does HIVs attack on T lymphocytes mean for them?

Answer 42

HIVs attack on T lymphocytes means;

the healthy number of uninfected T cell drops

the body’s immunological activity decreases

Question 43

what does the depletion of T lymphocytes mean for a person?

Answer 43

open to serious opportunistic infections

pneumonia and rare forms of cancer

Question 44

what happens after several years of infection by HIV?

Answer 44

person has extremely weakened immune system

suffers from AIDS