Innate Immunity

Question 1

Describe features of the innate immune system

Answer 1

• rapid response (minutes/hours)
• recognises a limited number of different structures characteristic to pathogens
• no change upon re-exposure

Question 2

Describe the features of the adaptive immune system

Answer 2

• takes time to develop (days/weeks)
• highly specific for a vast number of different structures
• response improves upon re-exposure

Question 3

What can a hematopoietic stem cell differentiate into?

Answer 3

• common lymphoid progenitor

- common myeloid progenitor

Question 4

What cells are involved in the innate response?

Answer 4

• NK cell
• dendritic cell
• monocyte
• neutrophil
• eosinophil
• basophil
• mast cell precursor

Question 5

What are the cells involved in adaptive response?

Answer 5

• T cell
• B cell
• Dendritic cell

Question 6

Where are monocytes released from?

Answer 6

-bone marrow

Question 7

When do monocytes differentiate into macrophages?

Answer 7

-when they leave the blood stream

Question 8

What are the main roles of monocytes?

Answer 8

to phagocytose and kill bacteria and to remove apoptotic cells

Question 9

What can macrophages recognise using what?

Answer 9

can use pattern recognition receptors (PRR) to recognise pathogen associated molecular patterns (PAMPS)

Question 10

How do macrophages kill bacteria in phagolysosomes?

Answer 10

• acidification
• production of oxygen and nitrogen radicals
• proteolytic enzymes

Question 11

How does antigen presentation occur?

Answer 11

• peptodes derived from killed microbes are presented to effector T cells, leading to their stimulation
• activated T cells will then support macrophages by soluble and surface-bound signals

Question 12

What are cytokines and where are they released from?

Answer 12

-small proteins released from activated macrophages

Question 13

What is the role of cytokines?

Answer 13

• to attract other immune cells to the site of infection,causing inflammation
• can act systemically and locally to activate antibacterial immunity

Question 14

What is the role of Kupffer cells?

Answer 14

remove circulating bacteria and apoptotic cells in the liver sinusoids

Question 15

What is the role of alveolar macrophages?

Answer 15

remove inhaled pathogens and other particles from the lungs

Question 16

What is the role of osteoclasts?

Answer 16

regulate bobe density

Question 17

What is the role of microglial cells?

Answer 17

scavenge dead cells, plaques and microbes in our brain

Question 18

What are the features of neutrophils?

Answer 18

• most abundant leukocytes
• short lifespan (1-3 days)
• circulate in blood unless recruited to site of infection
• phagocytose and kill bacteria
• vitally important in defence against bacteria

Question 19

When do neutrophils enter the tissue?

Answer 19

if they detect signs of inflammation displayed on the endothelium

Question 20

How do neutrophils enter tissues at the site of infection?

Answer 20

1. when inflammation occurs the vasculature express E-selectin proteins which the neutrophil recognise
2. the neutrophil slows down in the process of rolling
3. the neutrophils will then begin to react with other receptors (e.g chemokines and cytokines) this causes tight binding to the vasculature
4. the neutrophil them migrates through the endothelium
5. once inside the neutrophil migrates to the site of infection (follows gradient of CXCL IL-8)

Question 21

What does bacteria triggering macrophages lead to?

Answer 21

• the release of cytokines and chemokines
• vasodilation, increased vascular permeability (redness, heat swelling)
• inflammatory cells migrate into tissue, releasing inflammatory mediators that cause pain

Question 22

Describe how neutrophils respond on pathogens

Answer 22

1. engulf microbe
2. bacterial peptides activate Rac2 and bacteria are taken up in the phagosome
3. phagosomes fuse with primary and secondary granules Rac2 induces assembly of a functional NADPH oxidase in the phagosome membrane, leading to generation of O2-
4. acidification as a result of ion influx release granule proteases from granule matrix

Question 23

What are eosinophils, basophils and mast cells used for in innate immunity?

Answer 23

mainly involved in defence against pathogens that are too large to be phagocytosed such as parasites (also involved in allergic reactions)

Question 24

What are NK cells?

Answer 24

• natural killer cells
• recognise virally infected cells by recognising patterns specific for viral infection
• release granules to kill infected cells
• dead cells are removed by macrophages or neighbouring cells

Question 25

What is the role of dendritic cells?

Answer 25

-take up microbial material, migrate to lymph nodes and initiate T cell responses

Question 26

What is opsonisation?

Answer 26

increased phagocytosis of bacteria

Question 27

What happened when complement factors interact with bacterial surfaces or antibodies?

Answer 27

-cleavage and activation of these proteins
which contribute to:
-killing bacteria
-inflammation