6.3 The body’s response to infection

Question 1

what is lysozyme, where is it found and what does it do?

Answer 1

an enzyme found in tears and saliva that kills bacteria by breaking down their cell walls

Question 2

what triggers and inflammatory response?

Answer 2

invading microbes

Question 3

what are the effects of histamine?

Answer 3

arterioles in the area dilate and increase the permeability of the capillaries

Question 4

what is oedema?

Answer 4

swelling caused by plasma fluid, WBCs and antibodies leaking from the blood into the tissue

Question 5

what are phagocytes?

Answer 5

white blood cells that engulf bacteria and other foreign matter

Question 6

what are the two types of phagocytes?

Answer 6

neutrophils and macrophages

Question 7

what main three cells are in the blood?

Answer 7

platelets, RBCs and WBCs

Question 8

what attracts phagocytic white cells?

Answer 8

chemicals released by bacteria and damaged cells

Question 9

what are the first white blood cells to respond to an infected site and how many bacteria do they engulf?

Answer 9

neutrophils, they engulf 5-20 bacteria before they die

Question 10

how many cells can macrophages destroy?

Answer 10

around 100

Question 11

how do macrophages destroy bacteria?

Answer 11

by phagocytosis: ingested material is enclosed into a vacuole. lysosomes containing digestive enzymes bind with the vacuole and destroy the bacteria.

Question 12

what is pus?

Answer 12

dead cells, mainly neutrophils, that form a thick fluid

Question 13

what prevents the spread of bacteria that is carried in the blood and lymph?

Answer 13

the action of macrophages in the lymph nodes, spleen and liver

Question 14

what happens when the immune system fails?

Answer 14

septic shock

Question 15

what is interferon, where is it produced and how does it work?

Answer 15

it’s a protein produced by microbe-infected cells. it prevents microbes from multiplying by inhibiting microbial protein synthesis

Question 16

what are lymphocytes?

Answer 16

WBCs that defend the body against pathogens and are found in the lymph tissues

Question 17

what are the two types of lymphocytes?

Answer 17

B cells and T cells

Question 18

what do B cells do?

Answer 18

create antibodies that bind to antigens on the surface of pathogens that act as a label, allowing phagocytes to engulf them

Question 19

each different type of antibody has a different…?

Answer 19

amino acid sequence/binding site shape

Question 20

how many types of antibody does each B cell produce?

Answer 20

one

Question 21

What do B cells have on their membrane and why?

Answer 21

they have transmembrane receptors that are the same shape as the antibody they produce. each antigen will bind to and activate different B cells

Question 22

during embryo development, where are B cells produced?

Answer 22

bone marrow

Question 23

where are T lymphocytes produced and where do they mature?

Answer 23

produced in bone marrow, mature in the thymus gland

Question 24

what do T cells have on their surface?

Answer 24

antigen receptor

Question 25

what are the two types of T cells?

Answer 25

T helper cells and T killer cells

Question 26

what do T helper cells do?

Answer 26

when activated they stimulate the B cells to divide and become cells capable of producing many antibodies. Also enhance phagocyte activity

Question 27

what do T killer cells do?

Answer 27

destroy any cells with antigens on their surface that are recognised as foreign

Question 28

what happens when a piece of biological material is engulfed by a macrophage?

Answer 28

protein fragments from the material are added to the macrophages cell surface membrane and it becomes an antigen presenting cell (APC) which alert the immune system

Question 29

what are the receptors on T helper cells called?

Answer 29

CD4 receptors

Question 30

what do CD4 receptors do?

Answer 30

Bind to the antigen presented by the macrophage

Question 31

what do T helper cells do when their CD4 receptor binds to the APC?

Answer 31

it divides many times by mitosis producing a clone of active T helper cells and a clone of T memory cells

Question 32

how does the clonal selection of B cells happen?

Answer 32

APC B cells bind with active T helper cells that are presenting the same antigen. T helper cells real ease cytokines which stimulate division and differentiation of the B cells

Question 33

what are the two types of B cells that can be differentiated into due to cytokines?

Answer 33

B effector cells and B memory cells

Question 34

what do B effector cells do?

Answer 34

differentiate to produce plasma which releases antibodies into the blood and lymph

Question 35

what do B memory cells do?

Answer 35

remain in the body, ready for future infection

Question 36

what do T killer cells bind to?

Answer 36

an APC (body cell) that has the complementary antigen

Question 37

what happens with a T killer cells binds to an APC?

Answer 37

the T killer cell divides into two clones: active T killer cells and memory T killer cells

Question 38

how do T killer cells cause apoptosis of APCs?

Answer 38

T killer cells release enzymes that create pores in the membrane. ions and water enter causing the cell to swell and burst

Question 39

what happens to the pathogens in the APC after apoptosis?

Answer 39

the pathogens within the infected cell are released and labelled by antibodies

Question 40

what is the main cell needed in the secondary immune response?

Answer 40

memory cells

Question 41

what happens when a pathogen re-enters the body?

Answer 41

B memory cells immediately differentiate to produce plasma cells which release antibodies

Question 42

why do most people experience no symptoms when a pathogen re-enters the body?

Answer 42

anti bodies are produced sooner, quicker and at higher concentrations

Question 43

why does our immune system not attack the ‘self’ antigens on our own cells?

Answer 43

as B cells and T cells mature, any lymphocytes that have complementary receptors to ‘self’ antigens are destroyed by apoptosis