Pattern Recognition and Innate Immunity

Question 1

Describe cells involved in the innate immune response

Answer 1

neutrophils, macrophages, dendritic cells, mast cells, NK cells and complement
- all respond quickly and are nonspecific. Works to coordinate the adaptive immune response.

Question 2

Distinguish between inducible and non-inducible innate defenses

Answer 2

Non-inducible: things that are always in place
- physical - skin, membranes, mucous, commensal bacteria (resident flora(
- chemical - lysozyme, antimicrobial peptides
Inducible - things that need to be turned on
- innate immune cells: neutrophils, macrophages, dendritic cells, mast cells, NK cells
- neutralizing antibodies: secretly IgA

Question 3

How do innate immune cells recognize pathogens and how are they activates?

Answer 3

innate cells will recognize a pattern on all cells, however this doesn’t tell us which cells are pathogens, They also have to recognize a danger signal pattern at the same time (contents of a destroyed cell). The danger molecule can stimulate the immune response by itself as well.

Question 4

What are PAMPS?

Answer 4

Pathogens associate molecular patters
bacterial - LPS (gram -), peptidoglycan (cell wall), flagellin
viral - double stranded and single stranded RNA
fungal - chitin, zymosan

Question 5

What are DAMPS?

Answer 5

damage associated molecular patterns
anything that should be only on the inside of a cell. so if a cel gets injured/destroyed, its content will be spread everywhere.
- complement products - c3b, c4b
- ROS - H2O2, OH, O2-
- stress-indued molecules - heat shock proteins, chaperone proteins, lactoferrin, hyaluronic acid fragments - produced to destroy bacteria/parasites
-metabolic products - potassium, ATP, uric acid, cholesterol, saturated fatty acids
- nucleic acids - mRNA, ssRNA, chromatin components (histones)
-exogenous substances - alum, silica

Question 6

What are PRPs?

Answer 6

pattern recognition receptor - can be cell associated or unassociated 
 TLRs
NLRs
RIGS
CLRs
SRs
collectins

Question 7

Toll Like receptors

Answer 7

membrane bound receptors
highly expressed in phagocytes
activation leads to dendritic cell maturation, phagocytosis, cell activation
2,4,5 recognize bacteria pathogens
TLR2 - material peptidoglycan (pepTWOdoglycan)
TLR4 - LPS
TLR5 - bacterial flagellin 
3,7,8 recognizes viral RNA

Question 8

NOD like receptors

Answer 8

float around freely in cytoplasm
recognize PAMPS and DAMPS
Can form large complexes called infammasomes
- this help activate cascade 1 which cuts up really long proteins like IL-1 and IL-18 that are then activated after being chopped
activation leads to apoptosis and autophagy
work together with TLRs

Question 9

Retinoic acid inducible gene -1 receptors

Answer 9

free floating in cytoplasm
important for viral detection
recognizes viral RNA

Question 10

C-type lectin receptor

Answer 10

lectin is a protein that binds to a carb so pathogens often use it for attachment to a target cell
recognize carb-based DAMPS and PAMPS

Question 11

Scavenger receptors

Answer 11

binds to lipids (host or foreign)

Question 12

Collectins

Answer 12

Also do phagocytosis when activated
collagen domain fused to a lectin domain
found in blood and agglutinates things
they can activate complement

Question 13

Describe complement and understand its importance and function and how they are activated

Answer 13

serum based mechanism to destroy pathogens with NO cells involved (only proteins). part of innate response and occurs entirely in the serum of blood. it can be activated in 3 different ways (they all lead to activating C3b)
1) classical - antigen/antibody complexes (this is significantly delayed because the antibodies have to be made by the body)
2) lectin - mannose detecting ligand binds to a pathogen - quick
3) alternative - direct binding of C3 to a pathogen - quick
C3b is called can opsonin- like putting ranch on veg for kids so they eat a lot. If c3b is coating pathogens, phagosomes will readily eat it. IT can also help with solubility of immune complexes. They can get big and get stuck in blood vessels.
C5 is involved in the late stage complement activation

Question 14

Describe how cells are able to internalize and destroy microbes

Answer 14

Macropinocytosis - engulfing fluid “drinking”
Clathrin-mediated endocytosis - similar to “drinking” but its surface protein and receptor mediated
Phagocytosis - ingesting of large extracellular particles, and its receptor-mediated
Autophagy - cell recycling (activated by NODS)
- it is really good for the cleaning of intracellular pathogens like virus and some types of bacteria and parasites