Cells of the innate immune system Flashcards
What are the characteristics of the innate immune response?
Broadly specific
Doesn’t show immunological memory
Immediate
The immune system comes into play in most cases
TRUE or FALSE
FALSE
Most cases the immune system does not come into play since immunological barriers are very effective
Which cell gives rise to the innate immune cells?
Myeloid progenitor
What developmental pathway gives rise to the adaptive immune cells?
Myeloid developmental pathway
Where are Neutrophils found?
IN the blood and tissues
Where are Monocytes found?
In the blood
Where are Macrophages found?
IN the tissues
Where are Dendritic cells found?
In the tissues
Where are eosinophils found?
In the blood and tissues
Where are mast cells found?
In the mucosa and connective tissue
Where are basophils found?
In the blood
Where are natural killer cells found?
In the blood and tissues
Which cells are phagocytic?
Macrophages, monocytes, Dendritic cells and Neutrophils
Which cell is phagocytic and promotes inflammation?
Eosinophil
Which cells promote inflammation?
Mast cells and Basophils
Which cell kills virus infected cells?
Natural killer cells
Which types of cells does the myeloid progenitor give rise to?
Megakaryocytes Erythrocytes Dendritic cells Monocytes Leukocytes
What is a distinguishing feature of Natural Killer cells?
Form part of the innate immune system
But originate from the lymphoid progenitor cell
What are the 3 sentinel cells?
Neutrophils - in blood, migrate to tissue in response to infection = short lived
Monocytes - leave blood to form macrophages, live longer
Dendritic cells - many different cell types
Describe the process of phagocytosis
Chemotactic gradient attracts phagocyte to the zone of infection
Phagocytic cell comes into contact with pathogen
CSM recognition structure recognises structures of the infectious agent
PAMPs on pathogens bind to PRRs on phagocytic cells - adherence
Phagocytic cells activate via signals sent from the PRRs
Phagocytic cells release pseudopodia and engulf the pathogen
Pseudopodia fuse to form a vacuole and trap the pathogen - phagosome
Lysosomes move towards and fuse with phagocome to release lysozyme
This forms a phagolysosome
Lysosomes contain substances that destroy the trapped microbe
Release of degradation products
What are the ways in which the phagolysosome kills a pathogen
Oxidative killing - reactive oxygen species
Nitric oxide-related killing - reactive oxygen intermediates
Non-oxidative killing mechanisms - lysozyme breaks down the bacterial cell wall
What is the inflammatory response?
Process by which the phagocytic cell enters the zone of infection
Blood is the transport system - inflammatory mediators are released here to let cells know about the infection, so they can move from the blood into the tissues
What are the two inflammatory mediators used in the inflammatory response?
Inflammatory chemicals - histamines released by mast cells and basophils
Lipopolysaccharides - released by gram negative bacteria
Describe the process of the inflammatory response
Molecules are expressed which are not normally expressed
This leads to upregulation of P-selectin on vascular endothelium
Neutrophils recognise P-selectin by PSGL-1
Neutrophils adhere to the vascular endothelium and stops transit through blood
Neutrophils and vascular endothelium express adhsion molecules
Adhesion molecules released by the endothelium recognise those released by neutrophils = stronger adhesion
Neutrophils squeezes in between endothelial cells -> diapedesis
What adhesion molecules are expressed by the vascular endothelium and neutrophils?
Integrin
ICAM-1
E-selectin
What is diapedesis?
Process by which neutrophils squeeze in between endothelial cells
What is the role of eosinophils?
Phagocytic - not main job
Deals with organisms too large to be engulfed
How do eosinophils kill parasites?
Releases granules with toxic molecules to carry out extracellular killing
4 major molecules involved include
Major basic protein
Cationic protein
Oxygen metabolites
Perforins - punches holes in the surface of parasites
What are the roles of basophils and mast cells?
Responsible for allergy
Get rid of parasitic worms in the gut
How do mast cells and basophils do their function?
Work by coating in IgE - via FCE receptors that bind to Fc portions of antibodies
How does IgE work?
Antigen binding part of IgE = FAB
Sticks out from the mast cell/ basophil
When antigen comes along the IgE binds and recognises it
IgE links together and activates the basophil/mast cell
Release inflammatory mediators
What are the two types of inflammatory mediators released by mast cells/ basophils?
Ones that are stored in granules - histamine, serotonin
Ones that are newly synthesised - TNF-a, prostaglandin and leukotrienes
What is immunopathology?
Dangerous condition where an inflammatory response is targetted against a hermless agent
Can be dangerous
What did people think was the relationship between mast cells and basophils?
Mast cells = tissues
Basophils = blood
Thought that the two were related
Basophils differentiated into mast cells when moved into tissue
Wrong - both are terminally differentiated
What is the role of the NK cells?
Kill as much as possible in the body
Which two receptors are present on CSM of NK cells?
Activating receptor
Inhibiting receptor - specific for MHC I found on all cells
What is MICA?
Protein found on the membrane of some cells that bind to the activating receptors on NK cells
How do cells expressing MICA avoid apoptosis by NK cells?
MHC I on normal cells binds to inhibiting receptor on NK cells which overrides activating receptor
How do NK cells kill abnormal cells?
Abnormal cells lose expression of MHC-I receptors
SO they can no longer bind to inhibitor receptors on NK cells
NK cells recognise these as being abnormal - MICA still binds to the activating receptor
Some abnormal cells can also overexpress MICA/ activating SM proteins - overrides the inhibition signal by MHC I
Mechanisms of non-oxidative killing
Lysozyme
Defensins
Lactoferrin
Proteases
