MICRO 410 Exam 3 Questions and
Answers A+ Graded (2025)
Where .are .T .cells .developed? .- .CORRECT .ANSWER-Thymus .is .the .place .where
.T .cells .developed
What .is .a .naive .T .Cell? .- .CORRECT .ANSWER-A .naive .T .cell .is .mature .but .has
.not .met .up .with .its .specific .antigen. .It .will .travel .through .circulation .and
.lymphatics .searching .for .its .antigen.
T .cell .activation: .- .CORRECT .ANSWER-T .cells .require .antigen .presentation .as .a
.first .signal. .Other .molecular .interactions .can .provide .the .second .required
.activation .signal. .Once .activated, .T .cells .differentiate .into .their .effector .MHC
.forms .such .as .CD8+ .and .CD4+. .T .cells .go .on .to .become .killer .T .cells( .CD8+-
MHC .I) .or .T .cells .differentiate .into .several .different .subsets .(CD4+-MHC .II)
First .T .cell .activation .signal: .- .CORRECT .ANSWER-TCR/MHC-peptide
.complexes .and .coreceptors .are .reforced .and .centralize .and .activates .the
.Central .supramolecular .activating .complex, .cSMAC. .Adhesion .molecules/bound
.ligands .peripherally .localize .the .signal .and .activate .Peripheral .supramolecular
.activating .complex, .pSMAC.
Second .T .cell .activation .signal: .- .CORRECT .ANSWER-Costimulatory .ligands
.interaction .and .exchange .antigen.
Third .T .cell .activation .signal: .- .CORRECT .ANSWER-Cytokines .direct .T-cell
.differentiation .into .distinct .effector .cell .types .(paracrine .or .autocrine).
IL-2 .is .an .example .of .an .autocrine .type .of .cytokine .response .system.
IL-12 .is .an .example .of .a .paracrine .type .of .cytokine .response .system.
What .are .positive .costimulatory .receptors? .- .CORRECT .ANSWER-They .facilitate
.activation:
-CD28: .homodimer .expressed .on .majority .of .T .cells .and .enhances .TCR-induced
.proliferation .and .survival. .It .binds .to .B7-1(CD80) .and .B7-2 .(CD86) .expressed .by
.APCs
-ICOS: .binds .to .ICOS-ligand .on .activated .APCs. .Expressed .on .memory .and
.effector .T .cells .that .may .help .maintain .activity .of .already .differentiated .cells.
, What .are .negative .costimulatory .receptors: .- .CORRECT .ANSWER-Help .turn
.activation .off:
-CTLA-4(CD152): .Induced .within .24 .hours .after .activation, .peaks .2-3 .days .post-
stimulation. .It .binds .to .B7-1/B7-2 .with .higher .affinity .than .CD28, .but .shuts
.down .signaling .pathways. .
-PD-1 .(program .death-1, .CD279) .and .BTLA .(B- .and .T-lymphocyte .attenuator):
.PD-1 .may .help .to .mediate .T-cell .tolerance .in .nonlymphoid .tissues. .BTLA .may
.down-regulate .inflammatory .and .autoimmune .responses.
What .are .superantigens? .- .CORRECT .ANSWER-Produced .by .pathogenic
.Viral/bacterial .proteins .that .bind .to .specific .Vβ .regions .of .TCRs .and .α .chain .of
.class .II .MHC .molecules .and .act .as .a .defense .mechanism .against .immune
.system. .This .non-specifically .activates .T .cells .that .secrete .a .massive .amount
.of .cytokines.
What .is .the .difference .between .exogenous .and .endogenous .superantigens? .-
.CORRECT .ANSWER-Exogenous .superantigens .are .soluble .proteins .secreted .by
.bacteria. .Endogenous .superantigens .are .cell .membrane .proteins .generated .by
.viral .genes .integrated .into .mammalian .genomes.
T .cell .differentiation .signals(1-3) .- .CORRECT .ANSWER--(1-2 .days) .signals .1 .and
.2 .induce .upregulation .of .prosurvival .genes( .induces .the .cell .cycle), .activates
.transcription .of .IL-2 .and .IL-2R .genes, .and .leads .to .proliferation .(Production .of
.memory .and .effector .clonal .cell .populations .occur .between .4-5 .days). .
-Signal .3(Cytokine .signaling): .APCs .bind .PAMPS .via .PRRs, .inducing .cytokine
.secretion. .Different .PRRs .engaged .(via .different .antigens) .= .different .cytokines
.produced. .(Ex. .Viruses .stimulate .IL-12 .to .induce .TH1 .subsets, .Worms .stimulate
.IL-4 .to .induce .TH2 .subsets)
T .cell .differentiation: .Helper .T .cells .- .CORRECT .ANSWER-Helper .T .cells .can .be
.divided .into .five .distinct .subsets .(TH1, .TH2, .TH17, .TREG, .TFH). .Each .produces
.a .distinct .cytokine .profile .and .regulates .distinct .activities .within .the .body
Th1 .cell .differentiation .- .CORRECT .ANSWER-Naive .CD4+ .T .cell .are .induced .by
.IL-12, .IL-18, .and .IFN-γ .which .facilitate .induction .of .T-bet .master .regulator .in
.positive .feedback .loop. .Characterized .by .strong .IFN-γ .and .TNF .cytokine
.production, .which: .
.-Leads .to .class .switching .to .IgG .classes .that .support .phagocytosis .and
.complement .fixation
-Supports .differentiation .of .antiviral .CD8+ .killer .T .cells(DC's). .
(INTRACELLULAR .PATHOGENS)
Th2 .cell .differentiation: .- .CORRECT .ANSWER-Naive .CD4+ .T .cell .is .induced .by
.IL-4 .that .triggers .master .regulator .GATA3 .to .produce .Th2 .cells. .Th2 .cells
.upregulate .IL-4, .IL-5, .and .IL-13 .production. .IL-4 .acts .to .promote .activities .of
Answers A+ Graded (2025)
Where .are .T .cells .developed? .- .CORRECT .ANSWER-Thymus .is .the .place .where
.T .cells .developed
What .is .a .naive .T .Cell? .- .CORRECT .ANSWER-A .naive .T .cell .is .mature .but .has
.not .met .up .with .its .specific .antigen. .It .will .travel .through .circulation .and
.lymphatics .searching .for .its .antigen.
T .cell .activation: .- .CORRECT .ANSWER-T .cells .require .antigen .presentation .as .a
.first .signal. .Other .molecular .interactions .can .provide .the .second .required
.activation .signal. .Once .activated, .T .cells .differentiate .into .their .effector .MHC
.forms .such .as .CD8+ .and .CD4+. .T .cells .go .on .to .become .killer .T .cells( .CD8+-
MHC .I) .or .T .cells .differentiate .into .several .different .subsets .(CD4+-MHC .II)
First .T .cell .activation .signal: .- .CORRECT .ANSWER-TCR/MHC-peptide
.complexes .and .coreceptors .are .reforced .and .centralize .and .activates .the
.Central .supramolecular .activating .complex, .cSMAC. .Adhesion .molecules/bound
.ligands .peripherally .localize .the .signal .and .activate .Peripheral .supramolecular
.activating .complex, .pSMAC.
Second .T .cell .activation .signal: .- .CORRECT .ANSWER-Costimulatory .ligands
.interaction .and .exchange .antigen.
Third .T .cell .activation .signal: .- .CORRECT .ANSWER-Cytokines .direct .T-cell
.differentiation .into .distinct .effector .cell .types .(paracrine .or .autocrine).
IL-2 .is .an .example .of .an .autocrine .type .of .cytokine .response .system.
IL-12 .is .an .example .of .a .paracrine .type .of .cytokine .response .system.
What .are .positive .costimulatory .receptors? .- .CORRECT .ANSWER-They .facilitate
.activation:
-CD28: .homodimer .expressed .on .majority .of .T .cells .and .enhances .TCR-induced
.proliferation .and .survival. .It .binds .to .B7-1(CD80) .and .B7-2 .(CD86) .expressed .by
.APCs
-ICOS: .binds .to .ICOS-ligand .on .activated .APCs. .Expressed .on .memory .and
.effector .T .cells .that .may .help .maintain .activity .of .already .differentiated .cells.
, What .are .negative .costimulatory .receptors: .- .CORRECT .ANSWER-Help .turn
.activation .off:
-CTLA-4(CD152): .Induced .within .24 .hours .after .activation, .peaks .2-3 .days .post-
stimulation. .It .binds .to .B7-1/B7-2 .with .higher .affinity .than .CD28, .but .shuts
.down .signaling .pathways. .
-PD-1 .(program .death-1, .CD279) .and .BTLA .(B- .and .T-lymphocyte .attenuator):
.PD-1 .may .help .to .mediate .T-cell .tolerance .in .nonlymphoid .tissues. .BTLA .may
.down-regulate .inflammatory .and .autoimmune .responses.
What .are .superantigens? .- .CORRECT .ANSWER-Produced .by .pathogenic
.Viral/bacterial .proteins .that .bind .to .specific .Vβ .regions .of .TCRs .and .α .chain .of
.class .II .MHC .molecules .and .act .as .a .defense .mechanism .against .immune
.system. .This .non-specifically .activates .T .cells .that .secrete .a .massive .amount
.of .cytokines.
What .is .the .difference .between .exogenous .and .endogenous .superantigens? .-
.CORRECT .ANSWER-Exogenous .superantigens .are .soluble .proteins .secreted .by
.bacteria. .Endogenous .superantigens .are .cell .membrane .proteins .generated .by
.viral .genes .integrated .into .mammalian .genomes.
T .cell .differentiation .signals(1-3) .- .CORRECT .ANSWER--(1-2 .days) .signals .1 .and
.2 .induce .upregulation .of .prosurvival .genes( .induces .the .cell .cycle), .activates
.transcription .of .IL-2 .and .IL-2R .genes, .and .leads .to .proliferation .(Production .of
.memory .and .effector .clonal .cell .populations .occur .between .4-5 .days). .
-Signal .3(Cytokine .signaling): .APCs .bind .PAMPS .via .PRRs, .inducing .cytokine
.secretion. .Different .PRRs .engaged .(via .different .antigens) .= .different .cytokines
.produced. .(Ex. .Viruses .stimulate .IL-12 .to .induce .TH1 .subsets, .Worms .stimulate
.IL-4 .to .induce .TH2 .subsets)
T .cell .differentiation: .Helper .T .cells .- .CORRECT .ANSWER-Helper .T .cells .can .be
.divided .into .five .distinct .subsets .(TH1, .TH2, .TH17, .TREG, .TFH). .Each .produces
.a .distinct .cytokine .profile .and .regulates .distinct .activities .within .the .body
Th1 .cell .differentiation .- .CORRECT .ANSWER-Naive .CD4+ .T .cell .are .induced .by
.IL-12, .IL-18, .and .IFN-γ .which .facilitate .induction .of .T-bet .master .regulator .in
.positive .feedback .loop. .Characterized .by .strong .IFN-γ .and .TNF .cytokine
.production, .which: .
.-Leads .to .class .switching .to .IgG .classes .that .support .phagocytosis .and
.complement .fixation
-Supports .differentiation .of .antiviral .CD8+ .killer .T .cells(DC's). .
(INTRACELLULAR .PATHOGENS)
Th2 .cell .differentiation: .- .CORRECT .ANSWER-Naive .CD4+ .T .cell .is .induced .by
.IL-4 .that .triggers .master .regulator .GATA3 .to .produce .Th2 .cells. .Th2 .cells
.upregulate .IL-4, .IL-5, .and .IL-13 .production. .IL-4 .acts .to .promote .activities .of
