Review of the Innate Immune System Flashcards
(45 cards)
Why do we need an innate immune response?
Adaptive Immune Response is too slow to protect us from some new pathogens
Describe the speed of action of the adaptive immune response
Cytotoxic T cells activated for new infection after 3-4 days and antibodies after 5 days
Sufficient for slow growing bacteria (may take upto 6 days) before they start replicating at a dangerous level by which time the specific immune response will be under way
Why is adaptive immunity not sufficient for Influenza?
Influenza replicates every 4hrs - produce thousands of products rapidly
- requires innate immunity
Which type of immunity is required to resolve infections?
Resolution of infection requires both adaptive and innate immune responses
How does adaptive immunity work?
Adaptive involves very specific recognition of infectious agent (usually sees a protein = antigen)
Outline the specificity of innate immunity
Involves recognition of broadly conserved features of different classes of pathogens
- no specific antigen recognition
What are the components of innate immunity?
- Phagocytosis
- Inflammatory Response
- Cytokines, Interferons + Antimicrobial peptides (AMPs)
- Complement
- Intrinsic Defences – “the hostile cell”
- NK cells
Which immune cells carry out phagocytosis?
Carried out in vertebrates by Dendritic cells, macrophages and neutrophils
What is the role of phagocytosis?
Phagocytosis clears pathogens but also presents peptides on MHCs – this promotes development or reactivation of the adaptive immune response
How do macrophages carry out phagocytosis?
Material is destroyed in lysosomes
How do macrophages trigger an inflammatory response?
- Captured material triggers macrophage activation
- Activated macrophages produce cytokines and chemokines
- Stimulates both innate + adaptive immune responses
- Inflammatory response triggered; can promote a local antimicrobial state
What is an inflammatory response?
Generic defence mechanism
- Localises + eliminates injurious agents
- Removes damaged tissue components
What changes occur during an inflammatory response
- Enhanced permeability and extravasation
- Neutrophil recruitment
- Enhanced cell adhesion
- Enhance clotting
What 2 hormones do activated macrophages release?
Infected macrophage sends out 2 types of polypeptide hormones - cytokines and chemokines
How does the bloodstream aid inflammatory response?
Bloodstream supplies neutrophils and macrophages as well as normal RBCs etc.
Allows breakdown of capillary wall to allow more immune cells to get in to help break down pathogens
What are chemokines and cytokines?
Glycoprotein hormones that affect the immune response
What is the role of cytokines?
Act to modify the behaviour of cells in the immune response
Interleukins (eg. IL-1)
What is the role of chemokines?
Act as chemotactic factors
i.e. create concentration gradients which attract (or occasionally repel) specific cell types to a site of production/infection
How are pathogens recognised by phagocytes?
- Detecting phosphatidylserine on exterior membrane surface (cells undergoing apoptosis)
- By Scavenger receptors
- By some Toll-Like Receptors (TLRs)
- By passive sampling
How do phagocytes recognise pathogenic patterns?
Pattern recognition is through Pathogen-associated Molecular Patterns (PAMPs)
Why is PAMP recognition a good way to recognise pathogens?
PAMP molecules present on pathogens only; not on host cells
Essential for survival of pathogens
Invariant structures shared by entire class of pathogens
Outline common PAMPs
- Gram-ve bacteria; LPSs
- Gram+ve bacteria; teichoic acid, lipoteichoic acid, peptidoglycans
- Bacterial flagellin
- Abnormal protein glycosylation
- Abnormal nucleic acids - viruses
What are PRRs?
Pattern Recognition Receptors are host factors that specifically recognise a particular type of PAMP
How are PRRs encoded?
They are germ-line encoded
