MICB 4131 EXAM 3 QUESTIONS WELL ANSWERED LATEST UPDATE 2026
What are the three signals needed for T cell activation? - Answers 1. MHC/peptide + TCR
2. Co stimulation
3. Cytokine secreted by APC
What are the two molecules involved in costimulation for T cell activation? - Answers B7.1/B7.2
engages CD28
CD4 Th1 cells activate what type of cell? - Answers Macrophages
What do macrophages increase expression of? - Answers CD40 and TNF receptor
What do Th1 cells initiate if pathogens persist in macrophages? - Answers Granuloma (inflammatory
response)
In Leprosy, which T cell results in a tuberculoid, with normal T cell responsiveness? - Answers Th1
cells
In Leprosy, which T cell results in lepromatous, with low/absent T cell responsiveness? - Answers Th2
cells
What mechanisms do Treg CD4 T cells act through? - Answers 1. Cytokines IL-10 and TGFbeta
2. Killing effector T cells
3. Targeting DC
4. IL-2 scavenging --> AICD of activated T cells
What TF in mice causes autoimmunity when there is a gene knock-out? - Answers FoxP3
When does Treg development occur? - Answers During thymic development or after activation in SLO
Why would a T cell become a Treg cell instead? - Answers T cells that are self-reactive are deleted,
but can be converted to Treg cells as well
What is the induction of unresponsiveness in T cells that see self-Ag? - Answers Peripheral tolerance
What happens when Treg lacks? - Answers Autoimmunity
FOXP3 + IPEX
The overexpression of what TF can cure autoimmunity? - Answers FOXP3
if CTLA4 knockout + FOXP3 --> decreased autoimmunity
What T cell can aid in graft versus host disease? - Answers Treg cells
Do CD8 T cells need 3 signals for activation? - Answers Yes
What type of lytic granule aids in delivering contents of granules into the cytoplasm of the target cell?
- Answers Perforin
What type of lytic granule is a serine protease that activates apoptosis once in cytoplasm of the target
cell? - Answers Granzyme
What type of lytic granule has antimicrobial actions and can induce apoptosis? - Answers Granulysin
What ligand can mediate killing when upregulated by binding to a receptor on the target cell and
killing it via apoptosis? - Answers Fas ligand (FasL)
What are some pro-inflammatory cytokines that CD8 T cells secrete? - Answers IFN gamma and TNF
alpha
What cytokine inhibits viral replication, increases MHC I and peptide processing, and activates
macrophages and NK cells? - Answers IFN gamma
What cytokine induces fever, acute phase response, and contributes to macrophage activation? -
Answers TNF alpha
What are the specifics of CD8 T cell cytotoxic processes? - Answers Contact dependent and quick
Spare uninfected neighboring cells
What type of memory T cell recirculates through SLO? - Answers Central memory (Tcm)
What type of memory T cell is found in non-lymphoid tissue? - Answers Effector memory (Tem)
What type of memory T cell goes to a tissue and stays there? - Answers Resident memory (Trm)
What happens to T cells when chronic infections are present? - Answers T cell exhaustion/tolerance
T cells become non-functional/dysfunctional
What does ADCC stand for? - Answers Antibody dependent cell cytolysis
What cells are involved in ADCC? - Answers Neutrophils, NK cells, eosinophils, macrophages
How does ADCC work? - Answers 1. Antibody binds antigens on target cells
2. FcR on NK cells recognize bound antibody
3. Cross-linking of FcR signals NK cell to kill target cell
4. Target cell dies by apoptosis
, What are 2 example of applications of ADCC? - Answers 1. Ab specific for Herceptin induces ADCC of
tumor cells
2. Ab specific for CD20 is used to kill leukemias, lymphomas, and B cells
NK cells are similar to T cells except for what is lacking? - Answers Receptors -- not Ag specific
No memory formation
NK cells are similar to T cells in what way? - Answers Can kill target cells through the same
mechanism
Granzyme (DNA fragmentation) and perforin pathways - FAST
Fas-FasL pathway - SLOW
How are NK cells innate immune cells? - Answers Act to condition environment
How are NK cells adaptive immune cells? - Answers Secrete IL-12 and IFN gamma
What does a deficiency in NK cells lead to? - Answers Severe chickenpox and CMV infection
What are the 2 ways that NK cells can recognize target cells? - Answers 1. Recognize antibody coated
cells through ligation of antibody Fc portion through FcR on NK cells
2. Can sense the amount of MHC I on target cell --> when MHC I is down regulated (altered self), NK
cells lyse target cell
What are some events that lead to target cell death? - Answers 1. Conjugate formation
2. Membrane attack
3. CTL dissociation
4. Target cell destruction via apoptosis
The complement system is INNATE or ADAPTIVE? - Answers Innate immunity - NOT A PAMP
Some general properties of the complement system are: - Answers 1. Host derived but binds to
microbes
2. Enhances phagocytosis and inflammation
3. Helps Ab mediated bacterial clearance
What are serum proteins in the complement system composed of? - Answers C' proteins and liver
proteins
When is C' protein activated? - Answers When a pathogen/Ab coated pathogen is present
How to C' proteins kill pathogens? - Answers Directly or by inducing phagocytosis
C' proteins are zymogens which means: - Answers They cleave and activate each other
What are the 3 activation pathways of the complement system? - Answers 1. Classical (Ag-Ab
complexes)
2. Alternative (bacterial surfaces)
3. Lectin (MBL binding to lectins)
In the lectin pathway, what does activated MASP-2 do? - Answers Cleaves C4 into C4a and C4b which
bind to microbial surface
In the lectin pathway, what happens when C4b binds to C2? - Answers C4b2a complex is formed,
which is an active C3 convertase
Where are complement receptors found and what do they do? - Answers Found on APC to
phagocytose pathogens
Help place pathogen proteins in MHC binding groove
What two molecules disrupt C3 convertase C3bBb in order to not destroy C' proteins? - Answers DAF
and MCP
In the complement, what CD is responsible for preventing action of C8 on C9? - Answers CD58
What C3 convertase does the alternative pathway form? - Answers C3bBb
What C3 convertase do the classical and lectin pathways form? - Answers C4bC2a
What C5 convertase does the alternative pathway form? - Answers C3b(2)Bb
What C5 convertase do the classical and lectin pathways form? - Answers C4b2a3b
The complement system deposits a large amount of what on the pathogen surface for removal via
CR? - Answers C3b
What is the process of coating a pathogen/particle in order to enhance phagocytosis? - Answers
Opsonization
What do the byproducts of complement system activation do? - Answers Induce inflammation
What are inappropriate immune responses to an Ag called? - Answers Allergies
What is the tendency to be hyperallergic? - Answers Atopy
What happens during the development of IgE mediated allergies? - Answers Become sensitized to
harmless Ag by producing IgE against it
What are the three signals needed for T cell activation? - Answers 1. MHC/peptide + TCR
2. Co stimulation
3. Cytokine secreted by APC
What are the two molecules involved in costimulation for T cell activation? - Answers B7.1/B7.2
engages CD28
CD4 Th1 cells activate what type of cell? - Answers Macrophages
What do macrophages increase expression of? - Answers CD40 and TNF receptor
What do Th1 cells initiate if pathogens persist in macrophages? - Answers Granuloma (inflammatory
response)
In Leprosy, which T cell results in a tuberculoid, with normal T cell responsiveness? - Answers Th1
cells
In Leprosy, which T cell results in lepromatous, with low/absent T cell responsiveness? - Answers Th2
cells
What mechanisms do Treg CD4 T cells act through? - Answers 1. Cytokines IL-10 and TGFbeta
2. Killing effector T cells
3. Targeting DC
4. IL-2 scavenging --> AICD of activated T cells
What TF in mice causes autoimmunity when there is a gene knock-out? - Answers FoxP3
When does Treg development occur? - Answers During thymic development or after activation in SLO
Why would a T cell become a Treg cell instead? - Answers T cells that are self-reactive are deleted,
but can be converted to Treg cells as well
What is the induction of unresponsiveness in T cells that see self-Ag? - Answers Peripheral tolerance
What happens when Treg lacks? - Answers Autoimmunity
FOXP3 + IPEX
The overexpression of what TF can cure autoimmunity? - Answers FOXP3
if CTLA4 knockout + FOXP3 --> decreased autoimmunity
What T cell can aid in graft versus host disease? - Answers Treg cells
Do CD8 T cells need 3 signals for activation? - Answers Yes
What type of lytic granule aids in delivering contents of granules into the cytoplasm of the target cell?
- Answers Perforin
What type of lytic granule is a serine protease that activates apoptosis once in cytoplasm of the target
cell? - Answers Granzyme
What type of lytic granule has antimicrobial actions and can induce apoptosis? - Answers Granulysin
What ligand can mediate killing when upregulated by binding to a receptor on the target cell and
killing it via apoptosis? - Answers Fas ligand (FasL)
What are some pro-inflammatory cytokines that CD8 T cells secrete? - Answers IFN gamma and TNF
alpha
What cytokine inhibits viral replication, increases MHC I and peptide processing, and activates
macrophages and NK cells? - Answers IFN gamma
What cytokine induces fever, acute phase response, and contributes to macrophage activation? -
Answers TNF alpha
What are the specifics of CD8 T cell cytotoxic processes? - Answers Contact dependent and quick
Spare uninfected neighboring cells
What type of memory T cell recirculates through SLO? - Answers Central memory (Tcm)
What type of memory T cell is found in non-lymphoid tissue? - Answers Effector memory (Tem)
What type of memory T cell goes to a tissue and stays there? - Answers Resident memory (Trm)
What happens to T cells when chronic infections are present? - Answers T cell exhaustion/tolerance
T cells become non-functional/dysfunctional
What does ADCC stand for? - Answers Antibody dependent cell cytolysis
What cells are involved in ADCC? - Answers Neutrophils, NK cells, eosinophils, macrophages
How does ADCC work? - Answers 1. Antibody binds antigens on target cells
2. FcR on NK cells recognize bound antibody
3. Cross-linking of FcR signals NK cell to kill target cell
4. Target cell dies by apoptosis
, What are 2 example of applications of ADCC? - Answers 1. Ab specific for Herceptin induces ADCC of
tumor cells
2. Ab specific for CD20 is used to kill leukemias, lymphomas, and B cells
NK cells are similar to T cells except for what is lacking? - Answers Receptors -- not Ag specific
No memory formation
NK cells are similar to T cells in what way? - Answers Can kill target cells through the same
mechanism
Granzyme (DNA fragmentation) and perforin pathways - FAST
Fas-FasL pathway - SLOW
How are NK cells innate immune cells? - Answers Act to condition environment
How are NK cells adaptive immune cells? - Answers Secrete IL-12 and IFN gamma
What does a deficiency in NK cells lead to? - Answers Severe chickenpox and CMV infection
What are the 2 ways that NK cells can recognize target cells? - Answers 1. Recognize antibody coated
cells through ligation of antibody Fc portion through FcR on NK cells
2. Can sense the amount of MHC I on target cell --> when MHC I is down regulated (altered self), NK
cells lyse target cell
What are some events that lead to target cell death? - Answers 1. Conjugate formation
2. Membrane attack
3. CTL dissociation
4. Target cell destruction via apoptosis
The complement system is INNATE or ADAPTIVE? - Answers Innate immunity - NOT A PAMP
Some general properties of the complement system are: - Answers 1. Host derived but binds to
microbes
2. Enhances phagocytosis and inflammation
3. Helps Ab mediated bacterial clearance
What are serum proteins in the complement system composed of? - Answers C' proteins and liver
proteins
When is C' protein activated? - Answers When a pathogen/Ab coated pathogen is present
How to C' proteins kill pathogens? - Answers Directly or by inducing phagocytosis
C' proteins are zymogens which means: - Answers They cleave and activate each other
What are the 3 activation pathways of the complement system? - Answers 1. Classical (Ag-Ab
complexes)
2. Alternative (bacterial surfaces)
3. Lectin (MBL binding to lectins)
In the lectin pathway, what does activated MASP-2 do? - Answers Cleaves C4 into C4a and C4b which
bind to microbial surface
In the lectin pathway, what happens when C4b binds to C2? - Answers C4b2a complex is formed,
which is an active C3 convertase
Where are complement receptors found and what do they do? - Answers Found on APC to
phagocytose pathogens
Help place pathogen proteins in MHC binding groove
What two molecules disrupt C3 convertase C3bBb in order to not destroy C' proteins? - Answers DAF
and MCP
In the complement, what CD is responsible for preventing action of C8 on C9? - Answers CD58
What C3 convertase does the alternative pathway form? - Answers C3bBb
What C3 convertase do the classical and lectin pathways form? - Answers C4bC2a
What C5 convertase does the alternative pathway form? - Answers C3b(2)Bb
What C5 convertase do the classical and lectin pathways form? - Answers C4b2a3b
The complement system deposits a large amount of what on the pathogen surface for removal via
CR? - Answers C3b
What is the process of coating a pathogen/particle in order to enhance phagocytosis? - Answers
Opsonization
What do the byproducts of complement system activation do? - Answers Induce inflammation
What are inappropriate immune responses to an Ag called? - Answers Allergies
What is the tendency to be hyperallergic? - Answers Atopy
What happens during the development of IgE mediated allergies? - Answers Become sensitized to
harmless Ag by producing IgE against it
