W2L3 - Innate and Adaptive Immunity Flashcards
Functions of the Innate System
- Initial defence against microbes
- Eliminates damaged cells and initiates repair
- Stimulates adaptive immune response
- provides danger signals
- influence the type of adaptive response
How do the mucous membranes act as a surface barrier?
Trap microbes carried to external openings by ciliated epithelial cells
- cough reflex stops entry into RT
Anti-bacterial Peptides
Evolved early
Small (6-59) amino acids
+ charge
Defensins
- kill wide range of bacteria
- secreted by neutrophils, epithelial cells and paneth cells
- disrupt microbe membranes by binding and forming a pore which induces lysis
Inflammation
Important part of innate immune system Triggered by tissue/cellular injury Purpose: - prevent spread of agent - disposal of debris and pathogens - tissue repair - alerts adaptive immune response Over response can do damage
Main Signs of Inflammation
Redness Swelling Heat Pain Loss of function
Inflammatory Mediators
Cytokines
- proteins released by cells that affect other cells
- interleukins, interferons
Chemokines
- proteins released by cells that attract other cells to area
Acute-phase Proteins
- plasma proteins that increase in concentration due to inflammation within minutes
- c-reactive protein binds microbes and activates complement
Phagocytosis Steps
- Phagocytic cell recognises microbe, adheres and takes in microbe
- Held within phagosome which fuses with lysosome to form phagolysosome
- Toxic substance kill and degrade microbe (Nitric oxide, H2O2)
- Exocytosis to remove microbe debris
NK Cells
Eliminate both virally infected and cancer cells
Attack cells that lack self cell surface receptors
- NK cells recognise reduced MHC class 1 molecules via activating and inhibitory receptors
- Antibody Dependent Cell Mediated Cytotoxicity: NK cells can attach to antibodies on surface of cells
Stimulation of the Innate System
PAMPs
- pathogen-associated molecular patterns
- different structures on different pathogens that are recognised by cells on innate system
- stimulates response
- limited in number
DAMPs
- damage-associated molecular patterns
- molecules released from damaged cells
- released in response to trauma, toxin, burns, infection etc.
- healthy cells can release alarmins in response to infection which enhance response
Pattern Recognition Receptors (PRR)
Cellular phagocytes E.g. macrophages, DC, endothelial cells - when bind to PAMPs/DAMPS activate signal transduction pathways - promote inflammation and antimicrobial activity Soluble molecules - in blood and extracellular fluid - enhance phagocytosis - activate extracellular killing
NOD-like Receptors (NLR)
Specific for intracellular pathogens
- in the cytosol of cells
- activated by peptidoglycan, RNA, toxins and flagellin
- release pro-inflammatory cytokines
Interferons (IFN)
Broad spectrum anti-viral agents
3 groups:
- IFNα and IFNβ produced in response to viral infection
- IFNγ - inflammatory
Binds specific receptors of neighbouring cells
- neighbouring cells produces protein kinase R which blocks virus entry
- limits spread of viral infections
- stops production of protein in cell
- stimulates endonuclease production which degrades viral mRNA
What is Somatic Cell Recombination?
Multiple gene segments combined and recombined to form variations in protein binding of antigen
Action of Antibodies
Activate complement
Trigger phagocytosis
Neutralise viruses and toxins
Agglutination
Classes of Antibodies
IgG - monomer, most abundant - largest amount, long term immunity IgA - most abundant - saliva and mucosal surfaces, tears, milk IgM - pentamer - first Ab to appear during infection IgE - stem binds mast cells, basophils and eosinophils causing release of granules - allergies IgD - attached to B cells, antigen receptor for activation - largest Ab
