Unit 4

Question 1

What is immunity

Answer 1

the ability of the body to resist infection by a pathogen

or to destroy the organism if it succeeds in invading and infecting the body

Question 2

What are the two types of immunity?

Answer 2

non specific

specific

Question 3

what is a pathogen?

Answer 3

a micro organism that causes disease (fungi, bacteria, virus)

Question 4

what is an antigen?

Answer 4

proteins on the surface of cells.

used as a marker to identify a particular cell type

Question 5

The First Line of Defence

Answer 5

epithelial cell, which form your skin, provide the first line of defence against pathogens provided they remain in tact. the form a physical barrier.

Question 6

Chemical Defence (1)

Answer 6

secretions from the sebacous glands and sweat glands in the skin. keep the pH level that is too low for most pathogens

Question 7

Chemical Defence (2)

Answer 7

tears and saliva contain the enzyme lysozyme which digest the cell wall of bacterial cells

Question 8

Chemical Defence (3)

Answer 8

cells in the mucous membrane secrete sticky mucus that traps microorganisms

Question 9

Chemical Defence (4)

Answer 9

the epithelial cells in the stomach release acid which destroys microorganisms that have been swallowed

Question 10

Secondary line of defence - inflammatory response

Answer 10

when the body suffers physical injury it will respond with a localised defence called an inflammatory response

Question 11

what are phagocytes?

Answer 11

white blood cells that engulf and digest bacteria in a process called phagocytosis

Question 12

What do MAST Cells do?

Answer 12

release histamine causing vasodilation in blood vessels

Question 13

what do cytokines do?

Answer 13

signalling molecules which stimulate recruitment of other cell types

Question 14

Phagocytes

Answer 14

engulf pathogens and clean up the injured site

Question 15

Anti microbial proteins

Answer 15

amplify the immune response

Question 16

Clotting Elements

Answer 16

coagulation of blood helps to prevent further infection and starts tissue repair

Question 17

Stages of inflammatory response

Answer 17

• Physical injury
• mast cells activated and release histamine
• histamine stimulates vasodilation of the blood vessels in injured site
• blood vessels become more permeable leak fluid into neighbouring tissues causing swelling
• cytokines secreted
• migration of phagocytes to injured area/migration of antimicrobial proteins to injured area/delivery of blood clotting factors

Question 18

Natural Killer Cells

Answer 18

stimulate infected cells to commit suicide. apoptosis. infected cells are stimulated to produce a self destructive enzyme.
release cytokines that stimulate a specific immune response

Question 19

Specific Immunity

Answer 19

targets one particular pathogen.

involves T & B Lymphocytes

Question 20

Immune Surveillance

Answer 20

range of white blood cells move around body & constantly monitor the state of tissue.
if damage or invasion of microbes detected, white blood cells detect and release cytokines

Question 21

Antigens

Answer 21

any foreign molecule that is recognised by the immune system and produces a response from a lymphocyte.

Question 22

Antigenic Receptors

Answer 22

each lymphocyte has several copies of a single type of antigen receptor on the surface of the membrane.
lymphocyte specific to one antigen.

Question 23

Clonal Selection Theory

Answer 23

once lymphocyte detected.

dividing repeatedly to form a clonal population of identical lymphocytes

Question 24

Lymphocytes respond specifically to

Answer 24

Antigens on foreign cells
cells infected by pathogens
toxins released by pathogens

Question 25

Autoimmunity

Answer 25

autoimmune disease are a result of failure in regulation of the immune system leads to a T-Lymphocyte immune response to self cells

Question 26

Allergic Reaction

Answer 26

B Lymphocytes becoming hypersensitive to a normally harmless antigen
triggers an immune response which sensitises to the allergen.

Question 27

Helper T cells

Answer 27

secrete cytokines that activate phagocytes, cytotoxic t cells and B lymphocytes.
specific HTC then binds to the antigen on the antigen presenting cell.
HTC becomes activated & divides to produce a clone of activated helper cells.

Question 28

Cytotoxic T Cells

Answer 28

detect & destroy infected cells by several methods including apoptosis.

Question 29

Antigen Presenting Cells

Answer 29

after a phagocyte destroys an invading pathogen it presents fragments of its antigens on its cell surface.
phagocyte now referred to as an antigen presenting cell

Question 30

B lymphocytes

Answer 30

• the presence of an antigen triggers the production of antibodies by B Lymphocytes.
• An Antibody is a y-shaped protein, with each arm having a receptor that is specific to one antigen
• Antibody production by B Lymphocytes can occur following direct contact between the B cell & antigen
• B Cell displays molecules of foreign antigen it has taken in.