Innate Immunity 1 Flashcards
(26 cards)
What is innate immunity?
The first line of defence against infection. Present from birth and passed down through genes.
What are the different types of innate barriers:
Physical (e.g. skin and GI tract)
Soluble (e.g. complement, defensins and collectins)
Induced (e.g. innate immune cells, pattern recognition receptors (PRRs) and interferon)
What does complement do?
Enhances the ability of antibodies and phagocytic cells
What are defensins?
Host defence peptides
What are collectins?
Soluble pattern recognition receptors (PRRs)
What is interferon?
Signalling proteins made and released by host cells in response to a presence of a virus
What two types of factors get released when tissue damage occurs?
- Vasoactive (affects blood dilation)
- Chemotactic (causes cellular migration)
How do vasoactive factors lead to the destruction of bacteria?
1) Lead to increased blood flow and permeability at capillaries
2) More exudate and cells can enter
3) Phagocytes migrate to the site of inflammation (chemotaxis)
4) Phagocytes and antibacterial exudate then destroy the bacteria
How does complement work?
- Lyse bacteria
- Opsonise bacteria (mark them for phagocytosis)
- Induces inflammation
What are lysozyme and where are they found and released?
Enzymes that disrupt bacterial cell walls.
Found in blood and tears
Released phagocytes and Paneth cells from the small intestine
What do pentraxins, ficolins and collectins do?
Bind to pathogens and target them for phagocytosis and activate complement.
What do antimicrobial peptides do?
Disrupt bacterial membranes
How do lysozymes work?
Cleave the bonds between alternating sugars in peptidoglycan.
This makes them the most effective against gram-positive bacteria
What are some examples of antimicrobial peptides?
Histatins (activate against pathogenic fungi such candidas albicans)
Cathelicidins (LL-37 broad spectrum antimicrobial activity against both gram-positive and gram-negative bacteria)
Defensins
What are the two classes of defensins
alpha and beta
Why are defensins amphipathic peptides?
Because they have hydrophilic and hydrophobic regions
How do defensins disrupt the membranes of pathogens?
Form pores in the membrane
How do collectins bind to pathogens and what do they bind to?
Cell-surface sugars with their lectin-like globular heads
What do ficolins recognise?
Acylated compounds (COCH3), some of which are found in bacterial cell walls.
What type of pathways are the classical, lectin and alternative pathways?
Complement pathways
What do the complement pathways share in common?
All produce C3 convertase (C4b2a) within the pathway
What are the complement pathways made up of and where are they found?
Made up of over 30 proteins and they are constantly circulating in the blood and fluids that bathe the cells
How does the complement pathways lead to an amplification of a signal?
When it detects the presence of a foreign material, it initiates a cascade of reactions that amplify the signal.
What is C1 made up of?
C1q (majority), C1r and C1s
