CSIM 1.17 Innate and Acquired Immunity Flashcards
Name some of the components of the physical barriers in: • Skin • The gut • Lungs • Eyes
Skin
• Tight junctions
• Normal flora
• Antibacterial peptides
Gut • Tight junctions • Low pH • Enzymes • Normal flora
Lungs
• Mucus and cilia
• Tight junctions
Eyes
• Lysozymes in tears
What kills people in third degree burns?
Infection (not usually dehydration)
What causes increased infection in CF?
What disease has similar effects due to cilia being unable to function properly
Thick mucus cannot move and forms a breeding ground for pathogens
Cilial dyskinesia
Describe how normal flora may provide a bacterial barrier to pathogens
They can compete with pathogens for nutrients and produce antimicrobial substances
What is the symbiotic relationship of many different microorganisms called?
Microbiome
What is the second line of defence after physical barriers?
Innate immunity
• Proteins (e.g. complement)
• Cells (e.g. phagocytes)
What are the different names of macrophages based on where they are?
(Blood, Liver, Skin, CNS, Lungs)
What do all of these mature from?
Blood
• Monocytes
Liver
• Kuppfer cells
Skin
• Langerhans cells
CNS
• Microglial cells
Lung
• Alveolar macrophages
All mature from blood monocytes
What are neutrophils?
Another form of phagocyte (like macrophages) that are only found in infected or inflammed tissue.
They are confined to the blood until there is an infection
How do phagocytes differentiate self from non-self cells?
By identifying ‘pathogen-associated molecular patterns’ found on microbes but not human cells, using ‘pattern recognition receptors’
What are the different forms of pattern recognition receptors found on phagocytes?
What happens once these bind to pathogen-associated molecular patterns?
- Mannose receptor
- CD14 Lipopolysaccharide receptor
- Glucan receptor
- Scavenger receptor
- Toll-like receptor 4 (TLR-4)
The phagocytes (macrophages, neutrophils, etc.) do two things:
• Releases cytokines and mediators of inflammation
• They engulf and digest bacteria to which they bind
How is hydrogen peroxide produced in phagocytes?
What is this converted to?
- NADPH oxidase is activated and converts O₂ into O₂⁻ (called ‘superoxide’)
- Superoxide dismutase converts the superoxide into hydrogen peroxide
- This can further be converted into hypo-chlorite ions and hydroxyl radicals by peroxidase
What are the kinds of products formed by phagocytes which are bacteriocidal?
- Acid
- Oxygen products
- Toxic NO
- Antimicrobial peptides and enzymes
- Competitors (e.g. lactoferrin which binds Fe)
After phagocytosis, which structures fuse to begin the digestion of the pathogen, what does this form?
Phagosome and lysosome fuse to form phagolysosome
As for receptors other than pattern recognition receptors which bind to pathogens, what do these do? Give an example of one such receptor
Induce pro-inflammatory cytokines and chemokines
• TLR-4
• NFκB
Which cytokines are secreted by macrophages and dendritic cells? Which tissues does each act on primarily?
IL 1 & 6
• Lymphocytes
• Liver
IL 8
• Phagocytes
IL 12
• T-cells
Vascular endothelium
• TNF-α (induces inflammatory vascular changes)
How many TLR receptors are there? What do these recognise?
10
Characteristic components of pathogenic organisms not found in vertebrates
What feature of the immune system is complement a part of?
Describe what is meant by complement. What are the functions of it and which proteins are involved in each function?
Innate immune system
A distinct series of plasma proteins which tract with one another at sites of infection to:
- Involved in inflammation (C3a, C5a)
- Clearance of immune complexes (C3b)
- OPSONISE microbes with complement components for phagocyte binding (C3b)
- Form a membrane attack complex (MAC) to cause lysis of microbes (C5b, C6-C9) IMG 44
What are the names of the three biochemical pathways involved in the complement system?
- Classical pathway
- Lectin pathway
- Alternative pathway
What induces inflammation in the innate pathway?
What are the roles of these instigators in inflammation?
Phagocytes via TLR (and thus release of pro-inflammatory cytokines and chemokines)
• Causes expression of adhesion molecules
• Causes vasodilation
Complement (C3a, C5a)
• Makes the blood vessels permeable
How do leukocytes leave the blood into tissues at sites of inflammation?
- Cytokines produced by macrophages in the tissues cause dilation of blood vessels and expression of ADHESION MOLECULES in the endothelium
- Leukocytes bind to these adhesion molecules and extravasate at this site
What is the outcome of the processes of inflammation (e.g. increased blood flow, permeability, etc.)?
Allows additional effector molecules and cells to migrate to the site of infection to augment killing of invading microorganisms (e.g. neutrophils which are otherwise only found in blood)
Also prevents further spread of infection by blood through microvascular coagulation
Increased entry of plasma into the infected area and thus increased drainage of this into lymph nodes to enable the adaptive response
What is the primary role of dendritic cells?
These are the cells which are specialised to be antigen-presenting cells, and to migrate to the lymph nodes
Define what is meant by lymphocytes
CELLS WHICH MAKE UP THE ADAPTIVE IMMUNE SYSTEM:
• B cells
• T cells
What are the main characteristics of innate immunity? (speed, specificity and memory)
Rapid, non-specific and with no memory
What are the main characteristics of adaptive immunity? (speed, specificity and memory)
Delayed at over 96 hours, one antibody to one antigen, memory is retained
How many amino acids long are ‘antigens’?
8-12 aa
