Chapter 24 Flashcards
The innate and adaptive immune system (110 cards)
1
Q
Two branches of the immune system
A
Innate and Adaptive
2
Q
Innate Immune response
A
Activated directly by pathogens a
In all multicellular organisms
3
Q
Adaptive Immune response
A
Works with the innate immune system
Only vertebrates have
4
Q
Two responses of the adaptive immune response
A
- Antibody response (B cells)
- T-cell mediated response (T cells)
5
Q
Innate Immune System
A
First line of immune defense against pathogens
6
Q
PAMPs
A
Microbial structures not found in host cells that will trigger immune responses
7
Q
PRRs
A
Host receptors that detect PAMPs to initiate an immune response
8
Q
Toll - like receptors
A
Transmembrane PRRs
9
Q
NOD - like receptors
A
Cytoplasmic PRRs
10
Q
RIG - like receptors
A
Cytoplasmic PRRs
11
Q
C -type lectin receptors
A
Transmembrane, cell - surface PRRs
12
Q
Prostaglandins
A
Lipid signal molecules
13
Q
Cytokines
A
Protein/peptide signal molecules
14
Q
Pro-inflammatory cytokines
A
TNF-α, IFN-γ, IL1, IL6, IL12, IL17
15
Q
NF-κB activation
A
Induces transcription of cytokine genes
16
Q
Inflammasomes
A
Cytoplasmic NLRs complexed with adaptor proteins and caspases
Cleaves inactive cytokines to their active form
17
Q
Macrophages
A
Long lived phagocytes that resides in most tissues
18
Q
How does Macrophage activation occur?
A
PAMPs on microbes activate macrophages to secrete pro-inflammatory signal molecules
19
Q
Neutrophils
A
Short lived phagocytes that are abundant in blood but not present in healthy tissue
20
Q
Neutrophil recruitment
A
By signaling molecules at sites of infection
21
Q
Complement System
A
A group of ~ 30 soluble proteins that activate during infection to enhance immune response
22
Q
3 pathways of The Complement System
A
- Lectin
- Classical
- Alternative
23
Q
Early complement components
A
Each pathway has its own set of proteins
24
Q
Activation of complement proteins
A
Via proteolytic cleavage
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Transition step between Early and Late Complement Components
Activation of C3
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C3 activations
Leads to the recruitment of neutrophils to site of infection
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Late Complement Components
After the activation of C3
Forms membrane attack complexes
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Viral Replication Strategy
Viruses use host-cell machinery
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Viral PAMPs
Components of the viral genome
Double stranded DNA and large amounts of CpG motifs
30
What does dsRNA activate?
Intracellular PRRs and induce production of antiviral cytokines that are released and act upon uninfected neighbors
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Type I interferons
Block viral replication by degrading ssRNA and shutting down protein synthesis
Prevents viral replication
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MHC class I
Proteins present on nearly all nucleated cells
Used by NK cells to monitor cells health
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MHC I on virally infected cells
Virally infected cells express lower MHC I
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Dendritic cells
Provide the link between the innate and adaptive immune system
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Dendritic Cell Functions
Detect pathogens
Phagocytose and degrade pathogens into peptide fragments
Load fragments onto MHC proteins
Migrate to lymph nodes and activate T cells of adaptive immune
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Adaptive Immune System
System of lymphocytes that provides highly specific ad long lasting defense against pathogens
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Immunization
The process of inducing adaptive immune responses to pathogens or foreign molecules
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Antigen
Any substance that can stimulate a B or T cell to make a specific adaptive immune response against it
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Two broad classes of adaptive immune response
1. Antibody response
2. T-cell mediated immune response
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Antibody response
B cells secrete antibodies
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T-Cell mediated response
T-cells recognize peptides presented on MHC proteins
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Lymphocytes
Present in blood and lymph, concentrated in lymphoid organs
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What do lymphocytes arise from?
Hematopoietic stem cells found in bone marrow
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T-cell develop
In the thymus
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B-cell develop
In the bone morrow
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Primary/Central lymphoid organs
Thymus and bone marrow
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clonal expansion
Once a lymphocyte binds its specific antigen, then undergoes proliferation and differentiation into effector cells
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immunological memory
Lifelong immunity to infectious disease after out initial exposure to the pathogen
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Primary Immune Response
The immune systems first response to a pathogen
Takes several days
Response rises exponentially then gradually declines
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Secondary Immune Response
Second exposure to the pathogen
Shorter lag time due to memory cells
Greater more efficient response
Antigen specific response
Involves pre-existing B and/or T cells
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3 stages of maturation of lymphocytes in peripheral organs
1. Naive cells
2. Effector cells
3. Memory cells
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Naive cells
T or B cell that proliferates and differentiates into an effector or memory cell when it encounters a specific antigen for the first time
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Effector Cells
Cells that carry out an immune response
- B cells secrete antibody
- T cells kill infected cells or influenced the response of other immune cells
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Memory Cells
T or B cell generated following antigen stimulation that is more easily and quickly induced to become effector cells by a later encounter with the same antigen
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Lymphocyte recirculation
Continuous movement of B and T cells between blood, lymph, and peripheral lymphoid organs to look for pathogens
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Steps to lymphocyte entering a lymph node
1. Lymphocytes roll along blood vessels with weak adhesion
2. Chemokines released by specialized endothelial cells induces the lymphocyte to rapidly activate a stronger adhesion
3. Cells stop rolling
4. Lymphocyte the migrates out of the blood vessel and will migrate based on chemokine concentration gradients produced within the lymph node
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Chemokines
Signal molecules that attract B and T cells into lymph nodes and direct them to specific regions
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Where do chemokines lead B cells?
Lymphoid follicles
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Where do chemokines lead T cells?
Paracortex
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What happens is lymphocytes don't encounter an antigen?
Lymphocytes enter the medullary sinus and leaves the node via the efferent lymphatic vessel
Then enters the bloodstream to start circulation again
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Immunological Self-Tolerance
The adaptive immune system learns to not attack the bodies own molecules
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4 mechanisms of immunological self-tolerance
1. Receptor editing
2. Clonal deletion
3. Clonal inactivation
4. Clonal suppression
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Receptor Editing
B cell that recognizes self molecules
Changes antigen receptors so it no longer recognizes the self molecule
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Clonal Deletion
Potentially self-reactive B and T cells due by apoptosis when they encounter their self molecule
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Clonal inactivation
Self-reactive B and T cells becomes functionally inactivated when they encounter their self molecule
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Clonal Suppression
Self-reactive regulatory T cells suppress the activity of other types of potentially self-reactive lymphocytes
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Antibodies
Secreted proteins of the immunoglobulin class of proteins
Only produced by immune cells
Defenders against extracellular pathogens
68
Antibody function
Bind to viruses and microbial toxins
- Prevents then from binding to and damaging host cells
- Recruits components of the innate immune system to inactivate or eliminate the invaders
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First type of Ig produced by B cells
IgM and IgD
Not secreted as antibodies
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IgM and IgD
Insert themselves into their plasma membrane and serve as receptors (BCRs)
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BCR
Each has a unique binding site for antigens on B cells
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What is the first Ig produced?
IgM
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When do IgD start being produced?
Once the developing B cell leaves the bone marrow and migrates to peripheral lymphoid organs
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Ig structure
Bivalent with 2 identical antigen-binding sites
Made up of 4 polypeptide chains
N-term form the antigen-binding surface
C-term mediates activates of the other antibodies
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Mammals make 5 classes of Igs
IgA, IgD, IgE, IgG, and IgM
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What defines the different Ig classes
Their heavy chain
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Membrane bound Ig
C-term is hydrophobic and anchors into the lipid bilayer
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Soluble Ig
C-term is hydrophilic, allowing them to escape from the cell
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Variable regions of heavy and light chains
Come together to form the antigen-binding sites
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Hypervariable regions
3 regions that have the greatest diversity in the antigen binding region
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Preimmune, primary Ig repertoire
The billions of IgM and IgD molecules made by the B cells in the absence of antigen stimulation
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Class Switching
After stimulation by an antigen B cells switch from making IgM and IgD to making other classes of Ig
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Class switch recombination
An irreversible change at the DNA level when a B cell switches from making IgM and IgD to making one of the secondary classes of Igs
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Affinity maturation
Process by which the binding affinity of Igs made after antigen stimulation progressively increases over time
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Why does affinity maturation occur?
Due to point mutations that occur in both heavy and light chain V regions
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V gene segment
DNA sequence encoding the most variable region of an Ig peptide chain
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J gene segment
DNA sequence in the variable gene segment
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D gene segment
A short DNA sequence that encodes part of the heavy chain variable region of an Ig
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Light Chain Variable region
Assembled from a V gene segment and a J gene segment plus C region
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Heavy Chain Variable region
Assembled from a V gene, J gene, and D gene segment plus constant region
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V(D)J reccombinase
The enzyme that mediates V(D)J recombination
Active when a B cell's BCR binds strongly to a self-antigen
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T cell activation
ONLY activated by protein fragments presented by antigen-presenting cells
APCs must process the pathogen and present it
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Where do T cells work?
Short range
Within secondary lymphoid organs or sites of infection
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3 main classes of T cells
1. Cytotoxic T cells
2. Helper T cells
3. Regulatory T cells
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Cytotoxic T cells
Directly kill cells that are infected with a virus or intracellular pathogen
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Helper T cells
Help stimulate the response of other cells; usually macrophages, dendritic cells, B cells, and cytotoxic T cells
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Regulatory T cells
Suppress the activity of other immune cells
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T cell receptor
Membrane bound
2 polypeptide chains
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What is the professional APC?
Dendritic cells
100
How do dendritic cells activate T cells?
They display the antigen in a complex with MHC proteins on its surface
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How do immature DCs mature?
When their PRRs are activated
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3 types of proteins activated dendritic cells express
MHC proteins
Co-stimulatory proteins
Cell-cell adhesion molecules
103
MHC proteins
Present foreign antigen peptide to T cells
104
Co-stimulatory proteins
Bind to complementary receptors on T cell surface
105
Cell-cell adhesion molecules
Enable T cell to bind to the DC for long enough to become activated
106
MHC class I
Expressed by all nucleated cells
Present foreign peptides to cytotoxic T cells
Peptide binding groove is formed by the Alpha chain that associates with the Beta chain
107
MHC class II
Expressed only by APCs
Present foreign peptides to helper and regulatory T cells
Peptide-binding groove is formed by Alpha and Beta chains
108
Co-receptors
expressed on T cells and bind to invariant parts of MHC proteins
CD4 and CD8
109
CD8
expressed on cytotoxic T cells and binds to MHC I proteins
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CD4
Expressed on T helper cells and binds to MHC II proteins
