3.13 Innate and Adaptive Immune System Flashcards
What are the four mechanisms of innate immunity?
- Pattern recognition
- Leukocyte recruitment
- Phagocytosis
- Complement activation
___ are receptors of the innate immunity that recognize pathogen-associated molecular patterns on pathogens
Pattern recognition receptors (PRR)
T/F. The molecular pattern targeted by the PRR is produced only by the pathogen and never by the host
True
PAMPs are recognized by which immunity system?
Innate system
T/F. PAMPs are merely recognition sites for PRRs. They are not significant for the survival of microbes.
False. They are important for integrity and survival of microbes
Membrane spanning proteins that contain repeating segments of 24 to 29 amino acids containing leucine-rich repeats to their extracellular region
Toll-like receptors (TLRs)
What is the function of TLRs?
To recognize specific PAMPs
T/F. TLRs can be found in the outer and inner part of the cells.
True. TLRs for extracellular ligands are found on the surface (1,2,3,5,6), while TLRs for intracellular ligands are localized in intracellular component (3,7,8,9)
Process wherein leukocytes adhere to endothelial cells in affected regions and pass through the walls of capillaries and into the tissue spaces to migrate to the site of infection
leukocyte recruitment
Three steps of Leukocyte recruitment. Describe each.
- Rolling
- Binding
- Transmigration
The rolling step in leukocyte recruitment is mediated by what?
Selectin; attract leukocytes to site of infection
What happens during binding?
Integrins will be produced; leukocytes start to attach to basement membrane
What happens during transmigration?
Guided by chemokines, leukocytes go out of the blood vessel towards the tissue
Energy-dependent mechanism that involves the binding of phagosomes with lysosomes; this is also accompanied by other leukocytes in a multipronged attack
Phagocytosis
Phagocytosis employs
a) oxidative attack
b) nonoxidative attack
c) both
d) neither
C.
Oxidative attack involves __ and __
Reactive oxygen species and reactive nitrogen species
What generates ROS?
NADPH phagosome oxidase
A process wherein the oxygen consumed by phagocytes to support ROS production is provided by increasing the oxygen uptake of the cell several-fold
Respiratory burst
Four features of innate immune system
- Specificity
- Non-clonal distribution of receptors
- Discrimination of self and non-self
- Use of soluble recognition molecules
How is the specificity of the innate immunity dictated?
Encoded in the germline
Two kinds of anti-microbial peptides from the barriers
- Defensins
2. Cathelicidins
Where are defensins synthesized?
epithelial cells of the mucosa and granule containing leukocytes
Functions of defensins
direct toxicity
activate pathways of inflammation
Where do cathelicidins come from?
neutrophils and epithelial barriers; injury in epithelial cells causes an increase in the production of cathelicidins
Function of cathelicidins
Direct toxicity
Leukocyte activation
Specialized cells found in some linings of the body (GI) that helps one check fro intestinal infections
Intraepithelial lymphocytes
Two cellular components of the innate immune system
lymphocytes and phagocytes
Subset of B cells that produces phosphorylcholine and LPS IgM specific antibodies
B1 subset of B cells
Four kinds of phagocytes
Neutrophils
Monocytes/macrophages
NK cells
Dendritic cells
Usually the first to respond; can mediate any kind of infection, by releasing specific granules or enzymes released
Neutrophils
Azurophilic granules contain __ and __
defensins and cathelicidins
Specific granules contain __, __ and __
elastase, colleganase, lysozyme
T/F. Enzymes can dictate which kinds of infection the neutrophil can mediate earliest.
True
Phagocyte that can recognize infected and/or stressed cells; stimulates the maturation of the dendritic cells
NK cells
Two cytokines produced by NK cells
interferon gamma
tumor necrosis factor alpha
What is the function of interferon gamma?
mediator of macrophage activation and regulator of TH cell development
T/F. MHC Class I is normally present in healthy uninfected cells.
True
T/F. There are more MHC Class I in stressed cells.
False. They are reduced or absent in stressed cells.
Considered as early cellular responders to viral infection and they produce interleukin
Dendritic cells
Where are circulating effector proteins produced?
Liver
What are the functions of circulating effector proteins?
Recognition of bacteria and fungi; apoptotic cells; phosphorylcholine and phosphodiethanolamin in pathogens
causes opsonization and complement activation
Requirement for complement system to act
sequential proteolysis of proteins
3 pathways for activation of the complement pathway
classical
alternative
mannose binding
The classical pathway is triggered by
the activation of C1 complex
What composes the C1 complex, and what does it need to bind to in order for it to work?
C1q, C1r, C1s (proteases)
binding to two antibodies
What activated the alternative pathway?
Surface of the microbe
What are the 4 serum proteins involved in the alternative pathway?
C3, factor B, factor D, properdin
Proteins that recognize and bind to specific carbohydrate targets to their mannose residues
Lectins
T/F. The lectin/mannose binding lectin (MBL) pathway depends on antibodies for its activation
False
T/F. The MBL pathway, being a mannose binding lectin pathway, naturally ONLY activates during the binding to the mannose found on the surface of foreign cells.
False. MBL pathway also recognizes oligosaccharides thatare present in bacteria and yeast; fucose, glucose, acetylglocosamine present in parasites
Where the three complement pathways converge
Formation of the membrane attack complex
The formation of MAC involves which complement proteins?
C5b, C6, C7, C8, C9
The formation of MAC culminates in the formation of __ that produces __ and __.
C5 convertase
C5a
C5b
What binds to the surface of the target cell and provides a binding site for the subsequent components of the MAC?
C5b fragment from C5 convertase
The formation of MAC ultimately leads to the formation of a __ that changes the __ of the cell
formation of a PORE
that changes the OSMOLARITY of the cell
this eventually leads to cell lysis
A molecule that binds to both antigen and phagocyte thereby enhancing phagocytosis
Opsonin
What is the major opsonin of the complement system?
C3b
What are the four regulators of the complement system?
C1 inhibitor
Decay-accelerating factor
Factor I
CD59
What does the C1 inhibitor do?
C1 will bind to C1r and C1s, rendering C1q useless
What does DAF do?
Inhibits the coupling of C2b and C4b, thereby stopping the formation of C3 convertase
What does Factor I do?
Inhibits formation of C3 convertase by binding to C3b to render it inactive
What does CD59 do?
Binds to C5b and inhibit formation of MAC
What are the two signals that activate lymphocytes?
- Innate immune response to microbe attaching to an antigen receptor
- Induction of molecules in the innate response or stimulators
Characteristic of certain lymphocytes prefer to go to certain areas of the body where they are needed
Homing
Mechanism present in TH1 differentiation that drives the differentiation towards the TH1 phenotype
Positive amplification loop
Function of TH1
Phagocyte-mediated defense against infections through macrophage activation, complement binding and opsonizing antibodies and neutrophil activation
When does IL-4 activate transcription factor STAT6?
In response to microbes and antigens that cause persistent or repeated T-cell stimulation with little inflammation or macrophage activation
What is the master regulator of TH2 differentiation? What induces its expression? It enhances the expression of which cytokine genes?
GATA3
STAT6 and TCR
IL-4, IL-5, IL-13
GATA3 inhibits TH1 differentiation by:
inhibiting expression of the signaling chain of the IL-12 receptor
Function of TH2:
Promote IgE and eosinophil/mast cell-mediated immune reactions to protect against helminthic infections
Serine proteases that cleave proteins at aspartate residues
Granzymes
Facilitates delivery of granzymes into the cytosol of the target cell
Perforin
Assembles granzyme-perforin complex
Serglycin
IFN-Y can also stimulate which immunoglobulin?
IgG