CHP 2: Innate Immunity Flashcards
What are the three primary defense mechanisms of the innate immune system?
1) Physical barriers
2) Chemical barriers
3) Cells
What is purpose have having physical barriers?
To prevent infection and colonization
What is the purpose of chemical barriers?
To kill or inhibit microbial growth
What is the purpose of our innates cell function?
To recognize and destoy pathogens via phagocytosis
What events occur in our immune system during the first four hours after being exposed to a pathogen?
1) Physical and chemical barriers to prevent entry
2) Recruitment of innate immune system cells such as macrophages, neutrophils, and dendretic cells for phagocytosis
What are opsonins?
Extracellular molecules that tag bacteria or viruses to be destroyed or phagocytized by our immune system
Define PAMP
Pathogen associated molecule patterns: they are molecular patterns found on the surface of pathogens, these molecules are not associated with mammalian cells therefore play a key role in recognition of pathogens for our innate immunity
What is a phagolysosome?
Phagosome fusion with lysosome
What is the function of a phagolysosome?
create a low pH environment with digestive enzymes to destroy and degrade pathogens
What are the five steps of phagocytosis?
1) Recognition of pathogen via cell receptors
2) Clustering of receptors upon pathogen binding causing invagination of the phagocyte membrane
3) Internalization of pathogen via vesicle known as phagosome
4) Fusion of phagosome and lysosomes to form phagolysosome
5) Destruction and degradation of pathogen
Which receptors are responsible for recognizing PAMPs?
Pattern recognition receptors (PRRs)
Which molecules are characterized by a broad range of microbes and not normally present in the body?
Pathogen associated molecules patterns (PAMPs)
What are the types of innate immune cell receptors?
1) Toll-like receptors (TLRs)
2) Lectin receptors
3) Scavenger receptors
4) Cytosolic innate receptors
5) Opsonin receptors
Where can TLR be found?
Phagocyte cellular membranes and endosome membrane of these cells
Why do we have TLRs present our endosomes membranes?
To recognize intracellular pathogens such as viruses
Lectin receptors play a major role in which type of anti-pathogen immunity?
anti-fungal immunity
Lectin receptors bind to _______________.
Carbohydrates such as polysaccharides
Which receptor plays a role in cell adhesion?
Lectin receptors
Toll-like receptors are able to recognize which PAMPs?
1) Lipopolysaccharides (G-)
2) Lipoteichoic acid (G+)
3) Single and Double stranded RNA viruses
4) Bacterial proteins such as – flagellin, pilin
Define cytokines
Secreted proteins that have signaling roles in the immune response
Cytokines TNF-alpha and IL-1 are responsible for initiating which immune response?
Inflammation
Which cytokines are responsible for initiating an inflammatory immune response?
TNF-alpha and IL-1
Which type of cytokine is responsible for attracting immune cells to site of infection and inflammation ?
Chemokines
Give three examples of an antiviral cytokine
1) IL-12
2) interferon alpha
3) interferon beta
Which type of cytokine activates natural killer cells to find virus-infected cells and destroy them?
Antiviral cytokines such as interferons
T/F: Scavenger receptor and Lectin binding activate phagocytosis
True
Which cytosolic innate receptor recognizes viral RNA?
RIG-1
Which cytosolic innate receptor recognizes bacterial cell wall components in the cytosol?
NOD-like
Cytosolic innate receptors result in which cell responses?
1) inhibition of intracellular growth
2) recruitment of white blood cells such as NK cells
When does cell signaling occur?
receptor clustering to a pathogen triggers intracellular signaling pathways
What does cell signaling cause?
Changes in gene expression to produce and secrete cytokines
What antiviral proteins are activated by interferons?
1) Protein kinase R – inhibits protein synthesis
2) Induces RNAse L – destruction of all RNA within the cell
3) Induces P53 – triggering apoptosis
T/F: TLR’s are transmembrane proteins
True
Ligand binding by TLRs activate ______________ factors via signaling pathways
Transcription
TLRs that recognize ______________ PAMPS activate the transcription factor _________ resulting in ____________ and __________ expression
Bacterial; NFkB; phagocytosis; cytokine
TLRs that recognize intracellular nucleic acids activate transcription factors _________ and ________ via _____________ ____________.
IRF3 and IRF7; signaling pathway
Transcription factors IRF3 and IRF7 result in the production of?
Interferons and other pro-inflammatory cytokines
What inflammatory cytokines are produced by macrophages?
1) IL1 and TNF- alpha
2) IL-6
3) CXCL8
4) IL-12
The release of IL-1 and TNF-alpha results in?
increase in vascular permeability and induces fever
Which cytokines induce fever and increase vascular permeability?
IL-1 and TNF-alpha
What is the function of cytokine IL-6?
Induce fever and release acute phase proteins
CXCL8 is a ________ that attracts which innate immune cells?
chemokine; neutrophils and basophils
What is the function of IL-12?
Recruit and activate NK cells
What process do neutrophils use to exit the bloodstream?
Extravasation
What are the steps of extravasation?
1) Rolling adhesions via weak interactions between neutrophils and endothelial cells
2) Tight binding to LFA-1 and ICAM1 in response to chemokine CXCL8
3) Diapedesis: neutrophils cross the endothelial cell layer
Which two forms do neutrophils use to attack pathogens?
1) Respiratory burst (use of phagosome and expose pathogen to superoxide radicals)
2) NETS - trapping of pathogens with extracellular fibers of DNA and granules
How do our immune cells recognize infected cells versus healthy cells?
1) inhibitory responses – presents peptide fragments from inside the cell
2) Activating receptors – receptors on target cells that are in cellular stress to be destroyed or phagocytized.
How do NK cells recruit cytotoxic T cells?
Via cytokines such as IFN-gamma
