Communicable Disease, Prevention And Immunity - Cells Of The Immune System

Question 1

What are the two broad immune cells produced in bone marrow

Answer 1

• phagocytes
• lymphocytes

Question 2

What are the two kinds of phagocytes

Answer 2

• neutrophils
• macrophages

Question 3

What are the two kinds of lymphocytes

Answer 3

• T lymphocytes
• B lymphocytes

Question 4

Which is larger, macrophages or neutrophils

Answer 4

Macrophages

Question 5

Describe neutrophils

Answer 5

• able to squeeze through capillaries to patrol tissues
• first defenders on the scene of a bacterial invasion
• short lived cells

Question 6

How do macrophages begin

Answer 6

Leave the bone marrow and travel in the blood as monocytes, which develop into macrophages once they settle in organs

Question 7

Where are macrophages found

Answer 7

Organs

Question 8

Describe macrophages

Answer 8

• long lived cells
• become antigen presenting cells

Question 9

What are cytokines and what can they do

Answer 9

Cell signalling molecules
They can:
- increase body temperature
- attract phagocytes to the area
- stimulate the specific immune response

Question 10

What are antigens

Answer 10

• chemicals on the surfaces of cells
• usually composed of protein or glycoprotein
• can be molecules that our body recognises as foreign, on the surface of pathogens

Question 11

Are antigens always seen as foreign

Answer 11

No, can be self antigens

Question 12

Describe opsonins

Answer 12

• chemicals that bind to the antigens on pathogens
• they tag pathogens so that they are easily identified and engulfed by phagocytes

Question 13

Where do opsonins bind to phagocytes

Answer 13

Receptors on cell surface membrane

Question 14

Give an example of an opsonin

Answer 14

Antibodies

Question 15

What is the first step of phagocytosis in neutrophils

Answer 15

Opsonins attach to antigens on the surfaces of a pathogen

Question 16

What is the second step of phagocytosis in neutrophils

Answer 16

Receptors on the neutrophils attach to the opsonins on the pathogen

Question 17

What is the third step of phagocytosis in neutrophils

Answer 17

Neutrophils engulf a pathogen in a vesicle called a phagosome

Question 18

What is the fourth step of phagocytosis in neutrophils

Answer 18

Lysosomes fuse with the phagosome forming a phagolysosome

Question 19

What is the fifth step of phagocytosis in neutrophils

Answer 19

Enzymes within the lysosome completely digest the bacterium into smaller soluble molecules (may be absorbed into the cytoplasm by diffusion)

Question 20

What happens to waste products from digestion of bacteria

Answer 20

Removed by exocytosis

Question 21

Why is energy needed in the form of ATP for phagocytosis

Answer 21

• formation of vesicles
• moving vesicles along cytoskeleton

Question 22

What is the first stage of phagocytosis by macrophages

Answer 22

Antigen on pathogen attaches to receptor on macrophage

Question 23

What is the second stage of phagocytosis by macrophages

Answer 23

Pathogen is engulfed by phagocytosis and enclosed in a vesicle (phagosome)

Question 24

What is the third stage of phagocytosis by macrophages

Answer 24

Lysosomes fuse with phagosome, forming a phagolysosome

Question 25

What is the fourth stage of phagocytosis by macrophages

Answer 25

Pathogen is partially digested by hydrolytic enzymes within the lysosome Some products will be absorbed into cytoplasm by diffusion Fragments of antigen presented on surface

Question 26

What is the fifth stage of phagocytosis by macrophages

Answer 26

Indigestible material is removed by exocytosis The macrophage is now an antigen presenting cell

Question 27

What is the name of the DNA that codes for self antigens

Answer 27

MHC

Question 28

what are the three types of specific immune response

Answer 28

- antigen presentation - T lymphocyte activation (cell mediated immunity) - B lymphocyte activation (humoral immunity)

Question 29

where are T lymphocytes made and where do they mature

Answer 29

- made in bone marrow - mature in the thymus gland

Question 30

describe T lymphocytes

Answer 30

- they have receptors in their surface that are specific for a particular antigen - only recognise the antigen if it is presented with a self protein

Question 31

what are the two ways an antigen could be presented

Answer 31

- on an antigen presenting cell (macrophage) - on a body cell invaded by a virus (parts of virus on surface)

Question 32

what are the three steps of T lymphocyte activation

Answer 32

- antigen presentation - clonal selection - clonal expansion

Question 33

describe antigen presentation (cell mediated immunity)

Answer 33

macrophage engulfs, processes and presents antigen together with self protein

Question 34

describe clonal selection (cell mediated immunity)

Answer 34

- each T lymphocyte has a different receptor - when the complementary receptor binds, the antigen presenting cell releases cytokines that activate the specific T-lymphocyte

Question 35

describe clonal expansion (cell mediated immunity)

Answer 35

the activated T lymphocyte divides many times by mitosis forming a clone of identical T cells

Question 36

what are the three special types of T lymphocytes

Answer 36

- T helper lymphocytes - T killer lymphocytes - T memory cells

Question 37

describe the function of T helper lymphocytes

Answer 37

- secrete cytokines (interleukins) - cytokines bind to specific receptors on target cells - they act over short distances at very low concentrations

Question 38

what are the effects of the cytokines released by T helper cells

Answer 38

- stimulate B lymphocytes specific for this antigen - stimulate production of other types of T cells - attract phagocytes to the area

Question 39

describe the function of T killer lymphocytes

Answer 39

- destroy the cell which they bind to - produce a chemical called perforin which creates pores in the cell surface membrane so it is fully permeable, killing the cell

Question 40

describe the function of T memory cells

Answer 40

- remain in the blood - help the body to respond more quickly and effectively if the same antigen enters again by dividing rapidly to form clones of T cells to destroy the pathogen (faster clonal selection and expansion)

Question 41

where are B lymphocytes made and where do they mature

Answer 41

made and mature in the bone marrow

Question 42

describe B lymphocytes

Answer 42

they have cell surface embedded antibodies which act as receptors. they are specific for a certain antigen

Question 43

what are the three steps of B lymphocyte activation

Answer 43

- clonal selection - clonal expansion - differentiation

Question 44

describe clonal selection (humoral immunity)

Answer 44

when a specific B lymphocyte encounters an antigen that it has a complementary antibody for in its plasma membrane, it will become activated

Question 45

what can help activate some B lymphocytes

Answer 45

T helper cells, by releasing interleukins

Question 46

describe clonal expansion (humoral immunity)

Answer 46

the activated B lymphocyte divides many times by mitosis

Question 47

describe differentiation (humoral immunity)

Answer 47

B lymphocytes differentiate into plasma cells which produce antibodies

Question 48

describe plasma cells

Answer 48

- bigger cells - contain more organelles (rough ER, ribosomes, golgi) - synthesise the particular antibody they make - antibodies are released by exocytosis - only live for a few weeks

Question 49

what happens when antibodies bind to the pathogen

Answer 49

microbe marked for destruction, neutrophils will engulf and destroy

Question 50

what are B memory cells and what do they do

Answer 50

- remain in the blood - if the same antigen invades again, the body responds quickly (faster clonal selection, expansion and differentiation ) - the memory cells will develop into plasma cells that produce the correct antibody for the antigen