The Innate Immune System Part I – Pattern recognition Flashcards
What is Innate immunity compared to adaptive immunity ?
- It is more popular
- Also evolutionary older than adaptive immunity
Innate immunity is where in our defence ?
It is the frontline of our defences
Innate immunity includes what mechanism and defences ?
Innate immunity includes the basic barrier mechanisms and
simple biochemical defences
What cells does the innate immunity have ?
It includes immune cells (white blood cells) that recognise “general” pathogen molecules
Name some unique features of the innate immune system?
- 1st line of defence
- Present at birth, germline encoded
- Limited number of receptors recognising common patterns on pathogens/diseased tissue
- No memory of prior exposure - same response each time
- Instructs, induces & amplifies adaptive immune response
- Rapid: immediate response by preformed effectors then 48-96 hours for induced innate response
Explain some features of Inflammation ?
- A local response to injury or infection (damage/danger or pathogen)
- Recruitment of immune cells & molecules to kill infection / initiate repair
- Largely co-ordinated by leukocytes & leukocyte traffic
- Normally acute (short term)
Explain Neutrophils ?
- Most abundant white blood cell
- Short lived (hours)
- Dedicated phagocyte
- First line defence at site of infection
1. Degranulation of antimicrobial granule components
2. Neutrophil extracellular traps (NETs)
3. Initiate inflammation by releasing cytokines - Dead/dying neutrophils are a major component of pus (caused by what is known as pyogenic bacteria)
What are neutrophil NETs ?
Chromatin based fibres that trap & kill extracellular microbes
What does neutrophil NETs create ?
- Creates an antimicrobial environment at the inflammatory site
- Acts as a physical barrier contributing to killing of extracellular pathogens
Explain Eosinophils ?
- Characteristic eosin pink staining & bi-lobed nucleus
- Beneficial against parasitic infections
- Damaging part of the allergic response
- Recruited to tissues from blood at sites of inflammation
1. Release of anti-microbial factors
2. Potential to present antigens to T cells
3. Initiate inflammation by releasing cytokines that activate other cells
Explain Basophils ?
- Highly granular, blood circulating leukocyte
- <1% of all leukocytes
- Important in responses to parasites & allergy
- Recruited to sites of inflammation
- Become activated by cross-linking of surface bound antibody
- Activation induces degranulation and inflammatory mediator release
Explain Mast Cells ?
- Found in skin, blood vessels, connective tissue, mucosal tissue
- Large long-lived tissue-residents
- Very important in development of allergies
- Become activated by cross-linking of surface bound receptors with antibodies
1. Activation induces degranulation - histamine, leukotriene & prostaglandin release (vasoactive, smooth muscle contraction)
2. Inflammatory cytokine release, which promotes adaptive Th2 responses
What are Monocytes and it contains ?
- They are the blood precursor to tissue macrophages
- It contains nucleus, lysosome and phagosome
What are Macrophages and it contains ?
- They are specialised for phagocytosis & present antigens to T cells of adaptive immune system
- It contains Pseudopodia, Phagosomes, Lysosome and Phagolysosome
What are Dendritic cell and it contains ?
- They are the dendritic cells are the most potent antigen-presenting cells for T cells of the adaptive immune system
- It contains Phagosomes, Processes and Lysosome
Monocytes are recruited to ?
Tissues from blood at sites of inflammation where they differentiate into macrophages
Macrophages are professional phagocytes recognising & eating germs. What do they release ?
- Release of anti-microbial factors
- Release of pro-inflammatory cytokines
- Antigen presenting cell (APC) capacity
What do Pattern Recognition Receptors (PRR) enable ?
The discrimination between self and non-self
What do PRR recognise ?
PRR recognise simple molecules and molecular patterns specifically
associated with microorganisms known as Pathogen Associated
Molecular Patterns (PAMPs) – i.e., non-self
What can PRR also recognise?
Danger/Damage Associated Molecular Patterns
(DAMPs) - indicator self molecules specifically associated with cellular
infection, damage, stress or malignancy – i.e., self that has been somehow ‘transformed’
What receptors do Innate cells use ?
Pattern Recognition Receptors to recognise pathogens and discriminate from our own healthy cells
What are Pathogen Associated Molecular Patterns (PAMPs) ?
They molecular structures or molecules shared by most pathogenic microorganisms
What are Damage Associated Molecular Patterns (DAMPs) ?
They are molecular structures or molecules commonly found on damaged/necrotic/stressed tissue
How are PAMPs and DAMPs recognised ?
By innate Pattern Recognition Receptors (PRR)
