Immunity

Question 1

What are the 2 types of defence mechanism and what are their characteristics?

Answer 1

1) None specific- same response for all pathogens and it is immediate
2) Specific response- different response for all pathogens and it is slow

Question 2

What are the 4 main barriers to disease?

Answer 2

1) Epidermis of skin
2) Mucus membranes
3) Ciliated epithelia
4) HCl in the stomach

Question 3

What is phagocytosis?

Answer 3

The process by which pathogens are engulfed and destroyed by leukocytes

Question 4

Where are red, white and platelets cells formed?

Answer 4

The bone marrow

Question 5

What are the 2 types of phagocytes?

Answer 5

Neutrophils and Macrophages

Question 6

What are the 7 steps of phagocytosis?

Answer 6

1) Chemotaxis and adherence of microbe to the phagocyte
2) Ingestion of the microbe
3) Formation of a phagosome (vesicle + microbe)
4) Formation of a phagolysomes (lysosome + phagosome)
5) Digestion of ingested microbe by enzymes
6) The formation of the residual body which cannot be broken down by the enzymes
7) Discharge of material

Question 7

What are the 2 physical effects of phagocytosis?

Answer 7

1) Inflammation at the site of infection

2) Puss (dead bacteria + phagocytes)

Question 8

What causes inflammation?

Answer 8

The release of histamine which usually causes dilation of blood vessels

Question 9

What is the role of a T lymphocyte?

Answer 9

Respond to an organism own cells that have been invaded by foreign material

Question 10

What are antigen presenting cells?

Answer 10

Cells which present antigens of other cells on their own self surface membrane

Question 11

Where are T lymphocytes formed and stored?

Answer 11

Formed in the bone marrow and collect in the thymus

Question 12

What are 2 types of T lymphocytes?

Answer 12

1) T helper cells

2) T killer (cytotoxic) cells

Question 13

What are the 2 roles of T helper cells?

Answer 13

1) Formation of memory cells by mitosis

2) Cytokine secretion which stimulates phagocytes and B lymphocyte division

Question 14

What are the 2 roles of cytotoxic cells?

Answer 14

1) Produce a protein called Preforin which makes a hole in the membrane of the infected body cell
2) Secretes toxins to kill the cell

Question 15

What is the name given to an antibody + antigen?

Answer 15

Antigen-antibody complex

Question 16

What are the 4 functions of antibodies?

Answer 16

1) Prevent entry of viruses or toxins into the host cell
2) Immobilise bacteria by binding to flagella
3) Agglutinate bacteria
4) Coat bacteria which identifies them for phagocytosis

Question 17

What are the 3 ethical issues of monoclonal antibody formation?

Answer 17

1) Involves use of animals
2) Involves genetic engineering which some groups of people do not agree with
3) Introduction to the monoclonal antibody presents danger to the human

Question 18

Where are B lymphocytes produced and matured?

Answer 18

Bone marrow

Question 19

What is an antigen?

Answer 19

A molecule that produces an immune response

Question 20

What are the 4 steps in the humoral response?

Answer 20

1) Circulating antibodies will attach to antigens of the surface of the pathogen or toxin
2) T helper cells signals B cells to rapidly divide and form genetically identical daughter cells
3) Some daughter cells develop into plasma cells which produces large amounts of specific antibody
4) Other plasma cells become memory cells

Question 21

What happens in the primary immune response?

Answer 21

Plasma cells (short life span) secrete antibodies and memory cells (long life span) are produced which circulate in the blood

Question 22

What happens in the secondary immune response?

Answer 22

A smaller amount of antigen will induce an immune response because memory cells are present.

The response is more rapid and more antibody is produced.

Question 23

What are the 3 types of vaccination?

Answer 23

1) Live attenuated
2) Dead
3) Genetically engineered

Question 24

What is the herd immunity effect?

Answer 24

The effect of immunising a sufficiently large number of people to protect an entire population from the spread of a particular disease.

Question 25

What 3 factors contribute to the effectiveness of herd immunity?

Answer 25

1) Population density
2) Route transmission
3) Biology of the disease

Question 26

What are the 5 problems with vaccines?

Answer 26

1) Vaccine can cause disease and then can be passed on to others
2) People decline vaccines
3) Vaccines don’t work on everyone
4) Impossible to vaccinate against every disease
5) Pathogen may mutate often

Question 27

Why is control of cholera by vaccination difficult?

Answer 27

1) Cholera is an intestinal disease thus not easily reached by the immune system
2) Antigens of cholera mutate rapidly

Question 28

Why is control of TB by vaccination difficult?

Answer 28

1) Elderly population is increasing. They have less effective immune systems so vaccination is less effective
2) Mobile populations from the East due to poverty, wars and political unrest

Question 29

Why should scientific evidence be treated with caution?

Answer 29

1) Scientific theory should be critically appraised
2) Some scientist have vested interests
3) Media may portray evidence in a bias way