Innate Immunity

Question 1

What are the components of innate immunity?

Answer 1

Phagocytic cells - neutrophils, monocytes/macrophages
Natural Killer (NK) cells
Cell surface receptors
Complement system
Cytokines
Other soluble factors

Question 2

What innate protection does our body have?

Answer 2

Lysozyme in tears and urinary tract
removal of particles by rapid passage of air over turbinate bones
Bronchi - cilia serves to flap away and mucus to get rid of potential infection
Skin - acts as a physical barrier
Gut - acid
Flushing of urinary track
Low pH and commensals of vagina

Question 3

What are the types of epithelial barriers against infection?

Answer 3

Mechanical
Chemical
Microbiological

Question 4

Mechanical barriers against infection

Answer 4

movement of mucous by cilia
movement of air in the respiratory system

Question 5

Chemical barriers against infection

Answer 5

enzymes
e.g. lysozyme in salvia and tears
pepsin in the gut
antibacterial peptides

Question 6

Microbiological barriers against infection

Answer 6

commensal bacteria - are microbial barriers that compete for nutrients
they block adhesion and produce antimicrobial substances

Question 7

What happens if the body’s barriers are broken

Answer 7

Microbes invade

Question 8

What is a spot?

Answer 8

Inflammation and tissue damage caused by white blood cells that leave the blood and go into the skin to kill microbes growing in the wrong place.

Question 9

Where are Mucosal-associated Lymphoid tissues (MALT) found?

Answer 9

Found in interface between internal and external environment.

respiratory system, urogenital system, gut, mammary gland, lymphoid node and intestinal mocous

Question 10

What is the importance of the mucosal system?

Answer 10

Mucosal surface have an absorptive role
they act as a barrier against antigen penetration
they are able to respond to antigen penetration

Question 11

How are the tissues of the lymphoid system organised?

Answer 11

In sites where there is a potential for antigen entry

e.g. tonsils, adenoids, appendix, peyer’s patch, mucosal surfaces

Question 12

What are the roles of the cells in the mucosal system?

Answer 12

Slow down invasion of pathogens - when they ingest pathogens, serve as a signal to other parts that there is danger.

Question 13

What are the cells that leave the blood and get involved with the immune defence at the mucosal sites

Answer 13

Lymphocytes
Antigen presenting cells: langerhans, dendritic cells, macrophages
Neutrophils
NK cells

Question 14

What are the first cells at the scene of danger? e.g. infection/post trauma

Answer 14

Neutrophils (anti-inflammatory cells)

Question 15

On average, how many lobes does a normal neutrophil have?

Answer 15

average of 3 lobes
always lower than 5

Question 16

How do the neutrophils of patients with megablastic anaemia differ?

Answer 16

Have hyper-segmented nucleus in neutrophils
indicator of B12/folate deficiency

Question 17

Types of macrophages depending on the tissues they are found in?

Answer 17

Kupffer cells - liver
alveolar macrophages - lungs
microglial cells - brain
osteoclasts - bone

Question 18

What is opsonisation?

Answer 18

A method of increasing efficiency of phagocytosis

Question 19

What are opsonins?

Answer 19

Molecules that bind to the surface of foreign antigens

Question 20

Where are opsonin receptors found?

Answer 20

on the surface of phagocytes

Question 21

One a pathogen has been marked with opsonin, how is killing acheived?

Answer 21

Two ways:
1. Ingested and killed by an immune cell (phagocytosis)
2. Killed directly without ingestion

Question 22

Give examples of 3 types of Pattern Recognition Receptors and
their role in innate immunity

Answer 22

LPS receptor - bind lipopolysaccharide (endotoxin) on
surface of Gram-negative bacteria.

Mannose receptors - on macrophages (but not monocytes) and recognises yeast, bacteria and certain protozoa

Scavenger receptors (SRs): large family of cellsurface receptors can bind to a range of molecules (ligands)
of Gram-positive and Gram-negative bacteria.

Question 23

How to macrophages recognise PAMPs

Answer 23

through expression on pattern recognition receptors (PRRs) on the cell surface

Question 24

What do PAMP-PRR engagement lead to?

Answer 24

Phagocytosis
Production of cytokines and chemokines

Question 25

What happens when toll-like receptors bind to PAMPs

Answer 25

activates a range of signalling pathways - can lead to inflammation - key in natural immune response.

Question 26

Antimicrobial factors in Immunity

Answer 26

Salivary peroxidase - bactericidal effects and destruction of hydrogen peroxidase in mucosa that could otherwise cause tissue damage

Lysozyme - digests proteoglycans in bacterial cell walls

Lactoferin - iron-binding protein that blocking bacterial growth

Histatins - gets rid of fungal agents

Question 27

How do antimicrobial peptides work?

Answer 27

form pores in membranes of pathogens - water can then flood in causing the cell to burst

Question 28

What is the function Natural Killer Cells?

Answer 28

defend against viruses and tumours

Are cytotoxic - release toxic substances e.g. perforin and granzymes - involved in PCD

Express activation and inhibitory receptors that can sense pathological changes in self-cells.

Question 29

What are granzymes?

Answer 29

serine proteases that kill bacteria an inhibit viral replication.