Innate Immunity Flashcards
What are 2 examples of chemical defences?
- antimicrobial defenses (eg. defensins)
- enzymes (eg. lysozyme)
What’s an example soluble factors?
complement proteins
What are 4 examples of effector cells?
- granulocytes
- monocytes/macrophages
- DCs
- NK cells
How do effector cells work?
recognise pamps and activate more effector cells
How does lysozyme kill bacteria?
lysozyme catalyses hydrolysis linkages in peptidoglycan and digests cells wall, exposes cell membrane to outside
How do defensins kill bacteria?
defensins disrupt and lyse bacterial cell wall - attracted by electrostatic attraction
What is the key complement protein for marking a cell for destruction?
C3b
What are 3 outcomes of the complement system?
- migration of phagocytes to site of infection
- opsonisation and phagocytosis of microorganisms
- lysis of pathogens
What are the 3 stages of complement action?
- pattern recognition trigger
- protease cascade amplification/c3 convertase
- inflammation, phagocytosis, membrane attach
What are the 3 main complement pathways?
- alternative pathway
- lectin pathway
- classical pathway
Briefly explain alternative pathway
pathogen surface creates local environment conducive to complement activation
Briefly explain lectin pathway
mannose-binding lectin binds to pathogen surface
Briefly explain classical pathway
c-reactive protein or antibody binds to specific antigen on pathogen surface
What does C3b cause once bound to pathogen surface?
- recruits inflam cells
- opsonisation of pathogens (so, more uptake and killing by phagocytes)
- perforation of pathogen cell membranes
- eventually cell death
Explain the ‘stranger/danger’ idea used by effector cells
stranger - common microbial structure which are not usually seen in the body
danger - changes in expression of self proteins
How quickly do effector cells of innate system respond?
rapidly, minutes to hours
quick to act, quick to die
What are granulocytes (provide 3 examples)
characterised by secretory granules in cytoplasm
polymorphonuclear cells
neutrophils, basophils, eosinophils
What do neutrophils do?
phagocytosis and activation of bactericidal mechanisms
What do eosinophils do?
essential for killing parasites; control infection by releasing cytotoxic granules
What do basophils do?
drive innate immune response helping in anti-parasitic immunity
How do eosinophils and basophils help in parasite resistance (refer to their size)
because they are small granulocytes, they recognise certain parts of a parasite and release granules to remove that aprt
What are mast cells?
potent providers of histamine and cytokine release. associated with fighting parasites and inflam and allergen
What does mast cell degranulation cause?
vasodilation, promotes inflammation, recruitment, more lymph flow to lymph node, cause muscular contraction for physical expulsion
What are dendritic cells (DCs)
two types: migratory (mature), resident (resting)
sense pathogens, prevent antigen to T cells
What are NK cells?
derived from same progenitor cells as lymphocytes
secrete anti-viral cytokines, lyse cells via release of cytolytic granules
How does inflammatory response occur?
- surface wound introduces bacteria, activating effector cells which release cytokines
- vasodilation = more vascular permeability, so fluid, proteins, inflam cells leave blood and enter tissue
- infected tissue is inflamed, causing redness, heat, swelling, pain
What causes redness and heat in inflammation?
increase in vascular diameter and blood flow
What causes swelling in inflammation?
increase in vascular permeability means more fluid leaks into tissue
What causes pain in inflammation
inflammatory cells move into tissue, releasing mediators which stimulate nerve endings
What produces complement proteins?
liver cells, macrophages, monocytes, epithelial cells
