(5)Cell recognition and the immune system

Question 1

define a pathogen

Answer 1

a microorganism that causes disease

Question 2

what is immunity

Answer 2

the way in which the bodys defences are better prepared for a second infection from the same pathogen and so can kill it before it causes any harm

Question 3

what is a T cell or T lymphocyte

Answer 3

a type of WBC that has receptor proteins on its surface that bind to complementary antigens presented to it by phagocytes

Question 4

what is the difference between Tc cells and Th cells

Answer 4

Th cells (helper T cells) release chemical signals that activate and stimulate phagocytes and cytotoxic T cells (Tc cells) which kill abnormal and foreign cells

Th cells also activate B cells which secrete antibodies

Question 5

what are B cells/ B lymphocytes

Answer 5

a type of white blood cell that’s covered in antibodies . each B cell has a different shaped antibody on its membrane so different ones bind to different shaped antibodies

Question 6

what happens when a B cell antibody meets a complimentary antigen

Answer 6

they bind together, the B cell is activated because of substances released from helper T cells. The activated B cell divides into plasma cells

Question 7

what are plasma cells

Answer 7

identical to the b cell they secrete loads of antibodies specific to the antigen (called monoclonal antibodies)

Question 8

what is agglutination

Answer 8

an antibody has 2 binding sites so can bind 2 pathogens at the same time meaning pathogens become clumped together

Question 9

what are antibodies

Answer 9

proteins with a variable region that has a unique tertiary structure due to different amino acid sequences

Question 10

what are the 2 parts of the immune response

Answer 10

cellular- T cells and other immune system cells they interact with
humoral- B cells, clonal selection and the production of monoclonal antibodies

Question 11

what is the difference between memory B cells and memory T cells

Answer 11

memory T cells remember the specific antigen and will recognise it a second time round. memory b cells record the specific antibodies needed to bind the antigen

Question 12

what do memory B cells and memory T cells do during the secondary immune response

Answer 12

memory b cells are activated and divide into plasma cells that produce the right antibody to the antigen
memory t cells are activated and divide into the correct type of t cell to kill the cell carrying the antigen

Question 13

what is a vaccine

Answer 13

something that contains antigens that cause your body to produce memory cells against a particular pathogen without the pathogen causing disease so you become immune without having symptoms

Question 14

what is active immunity

Answer 14

the type of immunity where your immune system makes its own antibodies after being stimulated by an antigen. Natural: when you become immune after catching a disease
artificial : when you become immune after being given a vaccination

Question 15

what is passive immunity

Answer 15

the type of immunity you get from being given antibodies made by a different organism

natural: when a baby become immune due to antibodies it receives from mother from placenta and breast milk
artificial: when you become immune after being injected with antibodies from someone else

Question 16

what are moniclonal antibodies

Answer 16

antibodies produced from a single group of genetically identical B cells (plasma cells) so they’re identical in structure

Question 17

what does ELISA stand for

Answer 17

enzyme-linked immunosorbent assay

Question 18

what is the ELISA test used for

Answer 18

to see if a patient has any antibodies to a certain antigen or any antigen for a certain antibody. used to test for allergies or pathogenic infections

Question 19

what is the difference between direct ELISA and indirect ELISA

Answer 19

direct ELISA uses a single antibody that is complementary to the antigen that you’re testing for but indirect ELISA uses 2 different antibodies

Question 20

describe how monoclonal antibodies can be used to target a drug to cancer cells (4 marks)

Answer 20

1) monoclonal antibodies are made against antigens specific to cancer cells/ tumour markers
2) an anti cancer drug is attached to the antibodies
3) the antibodies bind to the antigens/tumour markers on cancer cells as their binding sites are complementary
4) This delivers the anti cancer drug to the cells

Question 21

what are 4 ethical issues surrounding vaccines

Answer 21

1) tested on animals and some animal based substances may be used to produce a vaccine
2) testing on humans - may be put at an unnecessary risk of contracting the disease if the vaccine didn’t work
3) some don’t take the vaccine because of side effects but are still protected because of herd immunity- may be seen as unfair
4) if there is an epidemic of a new disease there would be a rush to be vaccinated- difficult to decide who gets it first

Question 22

what is one ethical issue with monoclonal antibodies

Answer 22

animals are used to produce the cells from which the monoclonal antibodies are produced. Some disagree with this

Question 23

what is HIV and AIDS

Answer 23

HIV is a virus that affects the immune system and eventually leads to AIDS
AIDS is a condition where the immune system deteriorates and eventually fails so they are more vulnerable to other infections

Question 24

what does HIV do inside the body

Answer 24

infects and eventually kills helper T cells which act as host cells for the virus but helper T cells allow the immune system to effectively respond to infections as they send chemical signals that activate phagocytes, cytotoxic T cells and B cells

Question 25

at what point does HIV develop into AIDS

Answer 25

when the helper T cell numbers in the body reach a critically low level or symptoms of failing immune system start to appear

Question 26

what are the initial symptoms of aids

Answer 26

minor infections of mucous membranes and recurring respiratory infections then number of immune system cells decreases so they become more susceptible to chronic diarrhoea, severe bacterial infections and tuberculosis

Question 27

what are the final symptoms of aids

Answer 27

very low number of immune system cells so can develop serious infections such as toxoplasmosis of the brain, candidiasis of the respiratory system and these infections are what kill the patient

Question 28

how can the progression of HIV be slowed down

Answer 28

anti viral drugs

Question 29

what is clonal selection

Answer 29

the process where B cells divide into identical cells that produce antibodies