5.1- DEFENCE MECHANISMS

Question 1

What is any infection, in effect?

Answer 1

interaction between the pathogen and the body’s various defence mechanisms

Question 2

How can an individual die from a pathogen sometimes?

Answer 2

sometimes the pathogen overwhelms the defences

Question 3

How can the body recover from a disease?

Answer 3

body’s defence mechanism overwhelms pathogen and individual recovers

Question 4

How does the body overcoming a pathogen help it for next time?

Answer 4

body’s defences are better prepared for same pathogen + can kill it before it can cause any harm

Question 5

What is the body being able to kill the pathogen before it causes harm called?

Answer 5

immunity

Question 6

What is the main reason for why some people are unaffected by certain pathogen?

Answer 6

immunity

Question 7

Who will rarely die from an infection?

Answer 7

fit, healthy adult

Question 8

Who is more likely to die from an infection?

Answer 8

ill health, young and elderly usually more vulnerable

Question 9

What does the human body have to protect itself from pathogens?

Answer 9

range of defences

Question 10

What are the two types of defences the human body has?

Answer 10

general and immediate defences

more specific, less rapid but longer-lasting

Question 11

Examples of general and immediate defence? (2)

Answer 11

skin forms barrier to entry of pathogens

phagocytosis

Question 12

What do more specific, less rapid but longer-lasting response involve?

Answer 12

a type of white blood cell called a lymphocyte

Question 13

What two forms do more specific, less rapid but longer-lasting response take?

Answer 13

cell-mediated responses

humoral responses

Question 14

What do cell-mediated response involve?

Answer 14

T lymphocytes

Question 15

What do humoral responses involve?

Answer 15

B lymphocytes

Question 16

What must lymphocytes be able to do to defend the body from invasion by foreign material?

Answer 16

distinguish body’s own cells + molecules from those that are foreign

Question 17

What are the body’s own cells + molecules called?

Answer 17

self

Question 18

What are foreign material called?

Answer 18

non-self

Question 19

What would lymphocytes do if they were unable to distinguish body’s own cells + molecules from those that are foreign?

Answer 19

lymphocytes would destroy organism’s own tissues

Question 20

What does each type of cell, self or non-self have?

Answer 20

has specific molecules on its surface that identify it

Question 21

What is most important about the molecules (cells, self + non-self)?

Answer 21

proteins

Question 22

Why are the proteins the most important (cells, self + non-self)?

Answer 22

proteins have enormous variety + a highly specific tertiary structure

Question 23

What does the variety of specific 3D structure do? (cells, self + non-self)?

Answer 23

distinguished one cell from another

Question 24

What does the protein molecule allow the immune system to identify? (4)

Answer 24

pathogen i.e. HIV

non-self material i.e. cells from other organisms of same species

toxins including those produced by certain pathogens like bacterium that causes cholera

abnormal body cells i.e. cancer cells

Question 25

As pathogens, non-self material, toxins and abnormal body cells are all potentially harmful, what is the first stage of removing the threat they pose?

Answer 25

identification

Question 26

What complications can human who have had tissue/organ transplants have?

Answer 26

immune system recognises these as non-self even though they have come from individuals of same species

Question 27

What does the immune system try and do to transplanted tissue/organ?

Answer 27

attempts to destroy the transplant

Question 28

What is done to reduce the tissue rejection?

Answer 28

donor tissues for transplant normally matched as closely as possible to those of recipient

Question 29

Where do the best matches for tissue-organ transplants come from?

Answer 29

often come from relatives that are genetically close

Question 30

What are administrated to patients after organ/tissue transplants?

Answer 30

immunosuppressant drugs

Question 31

What do immunosuppressant drugs do?

Answer 31

reduce level of immune response that still occur

Question 32

Are specific lymphocytes produced in response to an infection?

Answer 32

no

Question 33

Do all specific lymphocytes already exist?

Answer 33

yes- all 10 million different types

Question 34

Given that there are so many different types of lymphocytes, what does this mean when a pathogen enters the body? (hint: probability?)

Answer 34

high probability that when a pathogen gets into the body, one of these lymphocytes will have a protein on its surface that's complementary to one of the proteins of the pathogen

Question 35

In other words, what happens when the lymphocyte has a protein on its surface that's complementary to one of the proteins on the pathogen?

Answer 35

lymphocyte will 'recognise' the pathogen

Question 36

As there are so many different lymphocytes, what are the numbers like of each type?

Answer 36

there are very few of each type

Question 37

As there are very few of each type of lymphocyte, what happens when an infection occurs?

Answer 37

the one type already present that has the complementary proteins to those of the pathogen stimulated to divide to build up its numbers

Question 38

Why does the one type of lymphocyte already present that has a complementary protein to those of the pathogen divide and build its numbers?

Answer 38

so it has numbers to a level where it can be effective in destroying it

Question 39

What is it called when the complementary lymphocyte to the pathogen divides to destroy it?

Answer 39

clonal selection

Question 40

What does clonal selection explain?

Answer 40

why there's a time lag between exposure to the pathogen and body's defences bringing it under control

Question 41

About how many different lymphocytes are present at any time?

Answer 41

around 10 million

Question 42

What is each type of lymphocyte capable of?

Answer 42

capable of recognising a different chemical shape

Question 43

In the foetus, what are the lymphocytes constantly doing?

Answer 43

constantly colliding with other cells

Question 44

Why is infection in a foetus rare?

Answer 44

because it's protected from the outside world by the mother, and in particular, the placenta

Question 45

As infection in a foetus s rare, what will the lymphocytes collide with?

Answer 45

collide almost exclusively with the body's own material (self)

Question 46

What will some of the lymphocytes have?

Answer 46

receptors that exactly fit those of the body's own cells

Question 47

What happens to the lymphocytes that have receptors that fit those of the body's own cells?

Answer 47

either die or are suppressed

Question 48

What are the remaining lymphocytes like, after the lymphocytes with receptors that fit the body's won cells are removed?

Answer 48

only remaining lymphocytes are those that might fit foreign material (non-self) and so only respond to foreign material

Question 49

What do lymphocytes produced in the bone marrow in adults initially only encounter?

Answer 49

only encounter self-antigens

Question 50

What happens to lymphocytes from the adult bone marrow that show an immune response to the self-antigens?

Answer 50

undergo programmed cell death (apoptosis) before they can differentiate into mature lymphocytes

Question 51

Will any clones of the anti-self lymphocytes appear in the blood?

Answer 51

no

Question 52

What is left as the clones of the anti-self lymphocytes do not appear in the blood?

Answer 52

leaves only those that might respond to non-self antigens