Innate Immunity Flashcards
What is innate immunity?
Immunity involving pretty much everything apart form lymphocytes and you have it form birth
Is innate immunity antigen specific? What can it recognise?
No, can recognise PAMPs or DAMPs using PRR
Which immune cell is particularly important in parasitic infections?
Eosinophils
Which type of infection are eosinophils important in?
Parasitic
Which immune cell is particularly important in releasing histamines?
Mast cells
Which immune cell is particularly important in lysing infected cells?
NK cells
Which two immune cells are most abundant and what %?
Macrophages and neutrophils (40-75%)
What do macrophages use to recognise targets?
Pattern recognition receptors
What are the three main ways the innate immunity system recognises pathogens?
PAMPs, DAMPs and detecting missing self
What type of cell usually detects missing self?
Natural killer cells
Which immune cells are first to the site of infection?
Neutrophils
What soluble mediators do macrophages disperse?
Cytokines
What type of nucleus does a neutrophil have?
Multilobed.
What are primary granules of a neutrophil?
Sites of the enzymes that will kill phagocytksed pathogens
What are secondary granules of a neutrophil?
Predominantly involved n replenishing primary granules and regulating the toxins produced during the lysis of pathogens
What is a phagolysosome?
A primary granule fused with a vacuole
What (4) steps does a neutrophil take to fight infection?
Move to pathogen, bind pathogen, phagocytose pathogen, and kill pathogen
What changes integrin to a high affinity binding state?
Chemokine receptor activation on the neutrophil
What helps the neutrophil roll along the surface of cells?
Low affinity binding of selectin
What is diapedesis?
Movement of a cell across the endothelial layer
What are the two main opsonins?
Antibodies and complement proteins
What is opsonisation?
Coating of a pathogen with proteins to facilitate phagocytosis
Whats the difference in antibody and complement binding?
Complement binds to the cell surface and antibodies bind to the receptor on the pathogen
What are neutrophil extracellular traps (NETs)?
• When neutrophils become highly activated they release these nets that help trap extracellular bacteria and immobilise them
Which are bigger, macrophages or monocytes?
Macrophages
What type of receptors do macrophages/monocytes?
PRR’s
What do cytokines do? Where are they released from?
Macrophages and they recruit other cells and activate subsequent adaptive immune responses
Why do cytokines have to be regulated strongly?
They have strong effects at low concentrations
What are the 5 types of cytokines?
Interleukins, interferons, chemokine, growth factor and cytotoxic
What do interferons do?
Anti-viral (replication) effects
What do interleukins do?
Messaging between leukocytes
What do chemokines do?
Chemotaxis and movement
What do growth factors do?
all cells of the immune system come from stem cells in the bone marrow, exposure to different growth factors which are a type of cytokine determines what the stem cell becomes
What type of pattern do dendritic cells recognise?
PAMP’s
What do dendritic cells secrete once activated?
Cytokines
Do complements need antibodies?
Yes, induces lysis of cell. Antibodies induce agglutination
Where are components of the compliment system mainly produced?
Liver, but also by monocytes and macrophages
What does the compliment system have a enzyme cascade system?
So that a small initial response can be rapidly amplified
When the initial precursor is activated what happens? Explain the enzyme cascade system
Initial precursor becomes an activated enzyme. This catalyses the cleavage of many molecules along the chain. This causes the molecule to become an enzyme which does the same thing to the next molecule in the cascade.
What three pathways of activation of the complement system are there? Explain each briefly
Classical - conformational change in the antibody when it binds leads to complement activation
Alternative - direct activation by the surface of pathogens themselves
Lectin pathway - lectin is a PRR and binds to carbohydrates only present on pathogens
What is the main complement component/opsonin?
C3 (active component C3b)
What happens when C3 is activated?
The membrane attack complex (MAC) is formed
What does MAC do?
Lyse cells
What do the cleaved products of enzyme precursors do?
They are pro inflammatory mediators that can activate mast cells
Three ways complement is controlled?
Components have very short half lives
Complement is diluted in body fluids
There are specific regulatory proteins which help regulate the activity of complement (e.g. CD59 is expressed by many normal cells to make them resistant to complement mediated lysis)
What four functions does complement have?
Lysis, opsonisation, activation of inflammatory response, clearance of immune complexes
What causes mast cell degranulation?
Inflammatory fragments binding to receptors on the mast cell
What do mast cells secrete? What is the met result of mast cell activation?
Histamine. Vasodilation and increased vascular permeability.
What do alarm cytokines do?
Increase vascular permeability
What are anaphylatoxins?
Proinflammatory mediators
What is the opsonin for monocytes?
Mannan-binding lectin
Do natural killer cells have antigen specific receptors?
No
What are the two types of cell recognition NK cells have?
Induced self (stress patterns of self proteins) and missing self (when a cell becomes infected their MHC expression is down-regulated)
