A naive CD4+ T cell is activated in a tissue environment rich in TGF-beta and later dampens inflammation. What cell type has it become?
A. Th17 cell
B. Tfh cell
C. iTreg cell
D. CTL cell

C. iTreg cell

Inducible regulatory T cells arise from which precursor population?
A. Naive Th cells
B. Mature plasma cells
C. Activated NK cells
D. Marginal-zone B cells

A. Naive Th cells

Which cytokine-rich environment favors inducible Treg formation?
A. IL-2 rich
B. IL-12 rich
C. IFN-gamma rich
D. TGF-beta rich

D. TGF-beta rich

iTregs are considered regulatory because they produce cytokines that do what?
A. Recruit neutrophils strongly
B. Restrain immune responses
C. Increase antigen presentation
D. Stimulate CTL killing

B. Restrain immune responses

Which cytokine pair is classically produced by iTregs in this material?
A. IL-4 and IL-5
B. IL-17 and IL-23
C. IL-10 and TGF-beta
D. TNF and IFN-gamma

C. IL-10 and TGF-beta

IL-10 binds receptors on APCs and reduces expression of which immune-sensing molecules?
A. PRRs
B. FasL
C. CD40L
D. IgE

A. PRRs

A macrophage exposed to IL-10 becomes harder to activate. Which mechanism best explains this?
A. Increased B7 expression
B. Increased Fas sensitivity
C. Increased CD28 signaling
D. Reduced PRR expression

D. Reduced PRR expression

IL-10 binding to APCs also reduces which co-stimulatory molecule family?
A. CD40L
B. B7
C. Fas
D. TLR9

B. B7

A patient overproduces IL-10 during infection. Which APC change would most impair naive T-cell activation?
A. Increased PRR expression
B. Increased antigen release
C. Reduced Fas receptor
D. Reduced B7 expression

D. Reduced B7 expression

TGF-beta dampens T-cell responses by reducing which T-cell property?
A. Proliferation rate
B. Antigen affinity
C. BCR crosslinking
D. Complement binding

A. Proliferation rate

TGF-beta reduces the effectiveness of which effector lymphocyte group?
A. Helper B cells
B. Follicular dendritic cells
C. Killer T cells
D. Marginal-zone B cells

C. Killer T cells

As an immune battle is won, immune activation decreases partly because less of what remains?
A. Host MHC
B. Foreign antigen
C. Plasma antibody
D. Naive lymphocytes

B. Foreign antigen

Reduced foreign antigen after pathogen clearance decreases activation of which systems?
A. Coagulation and fibrinolysis
B. Complement and clotting
C. Platelets and endothelium
D. Innate and adaptive

D. Innate and adaptive

A virgin T cell contains many checkpoint receptor proteins in its cytoplasm before activation. Which protein is this?
A. CTLA-4
B. PD-L1
C. B7
D. ICOSL

A. CTLA-4

After activation, CTLA-4 begins moving to the T-cell surface after approximately how long?
A. 30 minutes
B. 6 weeks
C. 2 days
D. 1 week

C. 2 days

B7 proteins on APCs bind which inhibitory receptor with very high affinity?
A. CD28
B. CTLA-4
C. Fas
D. PD-L1

B. CTLA-4

Compared with CD28, B7 has approximately how much greater affinity for CTLA-4?
A. 1000-fold
B. 10-fold
C. 2-fold
D. Equal affinity

A. 1000-fold

CTLA-4 dampens T-cell activation by outcompeting which activation receptor?
A. Fas receptor
B. PD-1
C. ICOS
D. CD28

D. CD28

Early in naive T-cell activation, B7 binding to CD28 primarily provides what signal?
A. Apoptotic signal
B. Trafficking signal
C. Activation signal
D. Antibody signal

C. Activation signal

As CTLA-4 increases on the T-cell surface, the T cell becomes progressively what?
A. More cytotoxic
B. Less activated
C. More chemotactic
D. Less antigen-specific

B. Less activated

Shortly after T-cell activation, another inhibitory receptor is upregulated. Which receptor is this?
A. PD-1
B. PD-L1
C. CD40
D. GlyCAM-1

A. PD-1

The ligand for PD-1 is which molecule?
A. CD28
B. B7
C. PD-L1
D. FasL

C. PD-L1

PD-L1 appears on the surface of which tissues?
A. Resting bone marrow
B. Thymic cortex
C. Germinal centers
D. Inflamed tissues

D. Inflamed tissues

PD-L1 restrains activated T cells that have been working for what duration?
A. Before antigen exposure
B. For some time
C. Only minutes
D. Since thymic selection

B. For some time

CTLA-4 and PD-1 are collectively called what?
A. Checkpoint proteins
B. Chemokine receptors
C. Adhesion molecules
D. Pattern receptors

A. Checkpoint proteins

Checkpoint proteins help do what as an immune battle winds down?
A. Activate naive T cells
B. Recruit neutrophils
C. Crosslink BCRs
D. Decommission T cells

D. Decommission T cells

Immune weapons help ramp down quickly after victory because many have what property?
A. Short half-lives
B. Permanent activation
C. Long telomeres
D. High antigen affinity

A. Short half-lives

Neutrophils have a typical half-life of approximately what duration?
A. 30 minutes
B. 6 weeks
C. 5 days
D. A few days

D. A few days

NK cells have a typical half-life of approximately what duration?
A. A few hours
B. 1 week
C. 6 weeks
D. 2 days

B. 1 week

Activated macrophages are maintained by IFN-gamma produced mainly by which cells here?
A. Plasma B cells
B. Dendritic cells
C. NK cells
D. Naive T cells

C. NK cells

When NK cells die off, activated macrophages tend to do what?
A. Return to resting state
B. Become plasma cells
C. Enter germinal centers
D. Express CTLA-4

A. Return to resting state

Dendritic cells live approximately how long after reaching a lymph node?
A. 2 days
B. 5 days
C. 6 weeks
D. 1 week

D. 1 week

Plasma B cells die off after approximately how long of labor?
A. 30 minutes
B. 5 days
C. 1 week
D. 6 weeks

B. 5 days

T cells require a special shutdown pathway partly because they naturally have what property?
A. Short half-life
B. No Fas receptor
C. Long lifespan
D. No antigen receptor

C. Long lifespan

The natural apoptosis pathway limiting repeatedly activated T cells is called what?
A. AICD
B. ADCC
C. DTH
D. MALT

A. AICD

AICD stands for which process?
A. Antigen-independent clonal division
B. Adaptive immune cell deletion
C. Antibody-induced complement destruction
D. Activation-induced cell death

C. Antibody-induced complement destruction

CTLs express which ligand that binds death receptors on target cells?
A. CD40L
B. Fas ligand
C. PD-L1
D. ICOSL

B. Fas ligand

Fas ligand on CTLs plugs into which receptor on target cells?
A. CD28
B. CTLA-4
C. Fas
D. B7

C. Fas

Virgin T cells are initially how responsive to Fas self-ligation?
A. Highly sensitive
B. Partially cytotoxic
C. Permanently apoptotic
D. Insensitive

D. Insensitive

After repeated activation and reactivation, T cells become more sensitive to what?
A. Fas self-ligation
B. BCR crosslinking
C. Complement opsonization
D. CXCL13 migration

A. Fas self-ligation

A repeatedly activated T cell dies when its own FasL binds its own Fas receptor. What process is this?
A. Somatic hypermutation
B. Self-ligation apoptosis
C. Antigen plucking
D. Class switching

B. Self-ligation apoptosis

A repeatedly activated T cell is killed when FasL on another T cell binds its Fas receptor. Which pathway is involved?
A. PD-1 blockade
B. CTLA-4 competition
C. Fas-mediated AICD
D. B7-mediated priming

C. Fas-mediated AICD

Once an invader is destroyed, approximately what fraction of responding T cells die off?
A. More than 90%
B. About 5%
C. Nearly 50%
D. Less than 10%

A. More than 90%

Which mechanism most directly explains massive T-cell contraction after pathogen clearance?
A. AICD through Fas
B. BCR crosslinking failure
C. Complement-mediated lysis
D. M-cell antigen sampling

A. AICD through Fas

Which molecule most directly reduces APC co-stimulation?
A. IL-10
B. IL-2
C. IL-17
D. IFN-gamma

A. IL-10

Which molecule most directly reduces T-cell proliferation?
A. TNF
B. IL-4
C. TGF-beta
D. IL-5

C. TGF-beta

Which mechanism best explains why activated macrophages stop fighting after NK cells decline?
A. Loss of IFN-gamma support
B. Increased BCR crosslinking
C. Increased plasma-cell labor
D. Loss of CTLA-4 storage

A. Loss of IFN-gamma support