4.1.5 secondary non-specific defences

Question 1

antigen-presenting cell

Answer 1

cell that isolates the antigen from a pathogen & places it on the plasma membrane so it can be recognised by other cells in the immune system

Question 2

clonal selection

Answer 2

selection of a specific B or T cell thats specific to the antigen

Question 3

cytokines

Answer 3

hormone-like molecules used in cell signalling to stimulate the immune response

Question 4

neutrophil

Answer 4

type of white blood cell that engulfs foreign matter & traps it in a large vacuole (phagosome) which fuses with lysosomes to digest the foreign matter

Question 5

opsonins

Answer 5

proteins that bind me to the antigen on a pathogen & allow phagocytes to bind

Question 6

what are secondary defences used for

Answer 6

combat pathogen that have entered the body

Question 7

what are antigens

Answer 7

chemical markers on the outer membrane of an invading pathogen

Question 8

describe antigens

Answer 8

• proteins or glycoproteins intrinsic to the plasma membrane
• specific to organism
• own cells have antigen but are recognised as our own & don’t produce a response

Question 9

what are opsonins a type of

Answer 9

antibody

Question 10

are opsonins specific

Answer 10

some aren’t so can attach to a variety of pathogenic cells

Question 11

role of opsonins

Answer 11

enhance ability of phagocytic cells to bind & engulf the pathogen

Question 12

what’s the first line of secondary defence

Answer 12

phagocytosis

Question 13

what’s the most common phagocytes

Answer 13

neutrophils

Question 14

what’s the nucleus of neutrophils like

Answer 14

multi-lobed

Question 15

where are neutrophils manufactured

Answer 15

bone marrow

Question 16

describe neutrophils

Answer 16

• travel in blood & often squeeze out via tissue fluid
• short-lived
• released in large numbers as result of infection
• contain large number of lysosomes
• engulf & digest pathogens
• die soon after ingesting few pathogens
• dead neutophils may collect in area of infection forming pus

Question 17

outline the process by which neutrophils engulf & digest pathogens

Answer 17

1. neutrophil binds to opsonin attatched to antigen of pathogen
2. pathogen’s engulfed by endocytosis forming a phagosome
3. lysosomes fuse to phagosome & release lytic enzymes into it
4. (after digestion) harmless products are absorbed into cell

Question 18

what are macrophages

Answer 18

• larger cells manufactured in bone marrow
• travel in blood as monocytes before settling in body tissues

Question 19

where are many monocytes found & what do they become

Answer 19

found in lymph nodes & mature into macrophages

Question 20

type of macrophage found in more peripheral tissues

Answer 20

dendritic cells

Question 21

important role of macrophages

Answer 21

initiate specific responses to invading pathogen

Question 22

what do macrophages do when they engulf a pathogen

Answer 22

does not fully digest it
- antigen from surface is saved & moved to special protein complex on surface of the cell
- the cell becomes an antigen-presenting cell (exposes the antigen on its surface so other cells in the immune system can recognise it)

Question 23

what does the special-protein complex ensure

Answer 23

that the antigen-presenting cell isn’t mistaken for a foreign cell & attacked by other phagocytes

Question 24

where does the antigen-presenting cell move & why

Answer 24

moves around the body where it can come into contact with specific cells that can activate the full immune response
- these are T & B lymphocytes
(may be only 1 of each with the correct recognition site for the antigen so these antigen-presenting cells increase the chances the antigen will come into contact with them)