JACI PRIMER EXAM 2023-2024 ACTUAL EXAM 120 QUESTIONS AND CORRECT DETAILED ANSWERS
1. Answer: B
Explanation: In virus-infected cells, some viral proteins are degraded in the cellular proteasome, the
major cellular protein degrading organelle. TAP-1 and TAP-2 are proteins that participate in the transport
of peptide fragments from the proteasome into the endoplasmic reticulum where they are loaded into
newly synthesized class I MHC molecules. Without TAP-1 or TAP-2, viral peptides are not loaded into
class I molecules, and recognition by CD8+ T cells does not occur. HLA-DM is required for peptide loading
into class II MHC molecules, permitting recognition by CD4+ T cells. B-lymphocytes must traffic through
the germinal center in order to undergo somatic mutation and differentiation to high affinity antibody
producing cells. Trafficking through the germinal center is not required for CD81 T cells devel- opment or
differentiation. Some viruses down-regulate (extinguish) expression of the class I prote - (answer)
Question 1. For CD8+ T lymphocytes to recognize virally infected cells, the infected cells must —
A. express functional HLA-DM molecules.
B. express functional transporter associated with antigen
presentation (TAP) 1 and 2 proteins.
C. have trafficked through a germinal center.
D. extinguish expression of its class I HLA molecules.
2. Answer: C
Explanation: Loading of peptide fragment from exogenous antigens into class II HLA molecules occurs
when the acidified endosome fuses with the class II loading compartment. This fusion results in the
proteolytic degradation of the invariant chain that then allows peptides to associate with the class II
molecules. The invariant chain is not associated with peptide loading into class I HLA molecules. The
invariant chain associates with the newly synthesized class II HLA molecules in the endoplasmic
reticulum. The invariant chain is designated as ÔinvariantÕ because is shows very low sequence
variability in different individuals in the population. - (answer) Question 2. The HLA invariant chain —
A. controls loading of viral peptide fragments into class I HLA molecules.
B. is delivered to HLA molecules in endosomes.
C. prevents loading of antigenic peptides into class II HLA
molecules until it is proteolytically degraded.
D. differs in primary amino acid sequence among different
subjects in the population.
3. Answer: D
,JACI PRIMER EXAM 2023-2024 ACTUAL EXAM 120 QUESTIONS AND CORRECT DETAILED ANSWERS
Explanation: b2-Microglobulin associates with class I MHC molecules and several other molecules with
class I-like structures. The MHC molecules that are the targets of TH cells (CD41 T cells) are class II MHC
molecules. These do not contain b2-microglobulin. The CD3 complex, rearranged a and b chains of the T-
cell receptor, and the CD4 molecule are all important components for recognition of peptide antigens
associated with class II MHC molecules. - (answer) Question 3. For TH cells, a functional T-cell receptor
requires all of the following except
A. the CD3 complex.
B. coexpression of CD4.
C. rearranged a and b chains.
D. b2-microglobulin.
4. Answer: C
Explanation: TLRs are found on many somatic cells, particularly ones that are involved in early contact
with microbes that invade the body through skin and mucosal tissues. The intracellular domains of TLRs
are homologous to the corresponding domains of the IL- 1 receptor. Most TLRs are cell-surface proteins,
but TLR3 and TLR9 are intracellular proteins that interact with their ligands during the intracellular part
of their lifecycle. TLR4 is activated by LPS. TLR9, in contrast, is activated by bacterial CpG DNA. -
(answer) Question 4. Which of the following statements is true?
A. The extracellular domains of Toll-like receptors (TLRs) are homologous to the corresponding domains
of the IL-1 receptor.
B. All TLRs are cell-surface proteins.
C. TLRs are found on macrophages, dendritic cells,
neutrophils, and endothelial cells.
D. TLR4 is activated by CpG DNA.
1. Answer: C
Explanation: Because TLRs are highly expressed on dendritic cells but not on T cells, the goal of TLR-
based therapies in patients with allergy and asthma is to activate dendritic cells to produce a cytokine
milieu (eg, IL-12 and interferons) that favors inhibition of the TH2 immune response. - (answer)
Question 1. Which of the following statements regarding activa- tion of Toll-like receptor (TLR) 9 in
allergic responses is true?
A. Activation of TLR9 expressed by eosinophils inhibits generation of prostaglandin D2.
B. Activation of TLR9 expressed by CD41 cells inhibits generation of TH2 cytokines.
C. Activation of TLR9 expressed by dendritic cells inhibits TH2 cell generation of cytokines.
,JACI PRIMER EXAM 2023-2024 ACTUAL EXAM 120 QUESTIONS AND CORRECT DETAILED ANSWERS
D. Activation of TLR9 expressed by endothelial cells inhibits recruitment of TH2 cells to sites of allergic
inflammation.
2. Answer: A
Explanation: IRAK4 deficiency is a novel primary immunodeficiency specifically affecting TLR function,
which is a component of the innate immune system. IRAK4 is involved in downstream signaling from
most TLRs. - (answer) Question 2. Which of the following human diseases is primarily caused by a
defect in the innate immune system?
A. IL-1 receptor-associated kinase 4 (IRAK4) deficiency
B. severe combined immunodeficiency (SCID)
C. X-linked agammaglobulinemia (XLA)
D. DiGeorge syndrome
3. Answer: D
Explanation: Flagellin is the ligand for TLR5. - (answer) Question 3. One recognition strategy used by
the innate immune system is to detect conserved microbial components. Which of the following is an
example of a well-characterized innate im- mune system receptor-ligand pair?
A. TLR4 and peptidoglycan
B. T-cell receptor and H1N1 influenza A peptide
C. caspase 1 and the muramyl dipeptide component of
peptidoglycan
D. TLR5 and flagellin
4. Answer: B
Explanation: The NLRP3 (NALP3) inflammasome is involved in mediating the adjuvant effects of alum.
This adjuvancy can occur directly through the triggering of the NALP3 inflammasome by alum crystals or
indirectly through release of the endogenous danger signal uric acid, which subsequently activates
NLRP3. - (answer) Question 4. Aluminum-containing vaccine adjuvants (alum) appear to mediate their
beneficial immunostimulatory effects through which of the following molecules of the innate immune
system?
A. TLR1/6 heterodimers
B. nucleotide oligomerization domain-like receptor family,
, JACI PRIMER EXAM 2023-2024 ACTUAL EXAM 120 QUESTIONS AND CORRECT DETAILED ANSWERS
pyrin domain-containing 3 (NLRP3, also called NALP3
or cryopyrin)
C. myeloid differentiation primary response gene 88
(MyD88)
D. killer cell immunoglobulin-like receptor (KIR)
1. Answer: C
Explanation: T-cell receptor activation leads to release of intracellular calcium stores, as well as influx of
extracellular calcium. Mature T cells express either CD4 or CD8 but not both. CD8 serves as a coreceptor
for MHC class I and not MHC class II molecules. The newborn screening for severe combined
immunodeficiency is performed by means of PCR quantitation of T-cell receptor excision circles on blood
spots. - (answer) Question 1. Which of the following statements concerning T cells is true?
A. On full maturation, T cells exiting the thymus express both CD4 and CD8.
B. CD8 serves as a coreceptor by binding to nonpolymorphic domains on MHC class II molecules.
C. T-cell activation leads both to release of intracellular calcium stores and to influx of extracellular
calcium.
D. Newborn screening for severe combined immunodeficiency is performed by counting T cells on a
blood spot.
2. Answer: D
Explanation: Natural killer T cells express markers of both T (ab) and natural killer (CD56) cells. CD251
regulatory T cells express forkhead box protein 3. RORgt is present in TH17 cells, which arise under the
influence of IL-6 and TGF-b. Target cell killing by cy- tolytic T lymphocytes is complement independent
and involves perforin, granzymes, and Fas-mediated apoptotic mechanisms. - (answer) Question 2.
Which of the following statements concerning ef- fector T cells is true?
A. CD251 regulatory T cells express the transcription factor retinoic acid receptor related orphan
receptor gt (RORgt).
B. TH17 cells arise from TH0 precursors under the influence
of IL-4 and IFN-g.
C. Killing of virally infected target cells by cytolytic T
lymphocytes is mediated by complement.
D. Natural killer T cells express abT-cell receptors and CD56.
1. Answer: B
Explanation: In virus-infected cells, some viral proteins are degraded in the cellular proteasome, the
major cellular protein degrading organelle. TAP-1 and TAP-2 are proteins that participate in the transport
of peptide fragments from the proteasome into the endoplasmic reticulum where they are loaded into
newly synthesized class I MHC molecules. Without TAP-1 or TAP-2, viral peptides are not loaded into
class I molecules, and recognition by CD8+ T cells does not occur. HLA-DM is required for peptide loading
into class II MHC molecules, permitting recognition by CD4+ T cells. B-lymphocytes must traffic through
the germinal center in order to undergo somatic mutation and differentiation to high affinity antibody
producing cells. Trafficking through the germinal center is not required for CD81 T cells devel- opment or
differentiation. Some viruses down-regulate (extinguish) expression of the class I prote - (answer)
Question 1. For CD8+ T lymphocytes to recognize virally infected cells, the infected cells must —
A. express functional HLA-DM molecules.
B. express functional transporter associated with antigen
presentation (TAP) 1 and 2 proteins.
C. have trafficked through a germinal center.
D. extinguish expression of its class I HLA molecules.
2. Answer: C
Explanation: Loading of peptide fragment from exogenous antigens into class II HLA molecules occurs
when the acidified endosome fuses with the class II loading compartment. This fusion results in the
proteolytic degradation of the invariant chain that then allows peptides to associate with the class II
molecules. The invariant chain is not associated with peptide loading into class I HLA molecules. The
invariant chain associates with the newly synthesized class II HLA molecules in the endoplasmic
reticulum. The invariant chain is designated as ÔinvariantÕ because is shows very low sequence
variability in different individuals in the population. - (answer) Question 2. The HLA invariant chain —
A. controls loading of viral peptide fragments into class I HLA molecules.
B. is delivered to HLA molecules in endosomes.
C. prevents loading of antigenic peptides into class II HLA
molecules until it is proteolytically degraded.
D. differs in primary amino acid sequence among different
subjects in the population.
3. Answer: D
,JACI PRIMER EXAM 2023-2024 ACTUAL EXAM 120 QUESTIONS AND CORRECT DETAILED ANSWERS
Explanation: b2-Microglobulin associates with class I MHC molecules and several other molecules with
class I-like structures. The MHC molecules that are the targets of TH cells (CD41 T cells) are class II MHC
molecules. These do not contain b2-microglobulin. The CD3 complex, rearranged a and b chains of the T-
cell receptor, and the CD4 molecule are all important components for recognition of peptide antigens
associated with class II MHC molecules. - (answer) Question 3. For TH cells, a functional T-cell receptor
requires all of the following except
A. the CD3 complex.
B. coexpression of CD4.
C. rearranged a and b chains.
D. b2-microglobulin.
4. Answer: C
Explanation: TLRs are found on many somatic cells, particularly ones that are involved in early contact
with microbes that invade the body through skin and mucosal tissues. The intracellular domains of TLRs
are homologous to the corresponding domains of the IL- 1 receptor. Most TLRs are cell-surface proteins,
but TLR3 and TLR9 are intracellular proteins that interact with their ligands during the intracellular part
of their lifecycle. TLR4 is activated by LPS. TLR9, in contrast, is activated by bacterial CpG DNA. -
(answer) Question 4. Which of the following statements is true?
A. The extracellular domains of Toll-like receptors (TLRs) are homologous to the corresponding domains
of the IL-1 receptor.
B. All TLRs are cell-surface proteins.
C. TLRs are found on macrophages, dendritic cells,
neutrophils, and endothelial cells.
D. TLR4 is activated by CpG DNA.
1. Answer: C
Explanation: Because TLRs are highly expressed on dendritic cells but not on T cells, the goal of TLR-
based therapies in patients with allergy and asthma is to activate dendritic cells to produce a cytokine
milieu (eg, IL-12 and interferons) that favors inhibition of the TH2 immune response. - (answer)
Question 1. Which of the following statements regarding activa- tion of Toll-like receptor (TLR) 9 in
allergic responses is true?
A. Activation of TLR9 expressed by eosinophils inhibits generation of prostaglandin D2.
B. Activation of TLR9 expressed by CD41 cells inhibits generation of TH2 cytokines.
C. Activation of TLR9 expressed by dendritic cells inhibits TH2 cell generation of cytokines.
,JACI PRIMER EXAM 2023-2024 ACTUAL EXAM 120 QUESTIONS AND CORRECT DETAILED ANSWERS
D. Activation of TLR9 expressed by endothelial cells inhibits recruitment of TH2 cells to sites of allergic
inflammation.
2. Answer: A
Explanation: IRAK4 deficiency is a novel primary immunodeficiency specifically affecting TLR function,
which is a component of the innate immune system. IRAK4 is involved in downstream signaling from
most TLRs. - (answer) Question 2. Which of the following human diseases is primarily caused by a
defect in the innate immune system?
A. IL-1 receptor-associated kinase 4 (IRAK4) deficiency
B. severe combined immunodeficiency (SCID)
C. X-linked agammaglobulinemia (XLA)
D. DiGeorge syndrome
3. Answer: D
Explanation: Flagellin is the ligand for TLR5. - (answer) Question 3. One recognition strategy used by
the innate immune system is to detect conserved microbial components. Which of the following is an
example of a well-characterized innate im- mune system receptor-ligand pair?
A. TLR4 and peptidoglycan
B. T-cell receptor and H1N1 influenza A peptide
C. caspase 1 and the muramyl dipeptide component of
peptidoglycan
D. TLR5 and flagellin
4. Answer: B
Explanation: The NLRP3 (NALP3) inflammasome is involved in mediating the adjuvant effects of alum.
This adjuvancy can occur directly through the triggering of the NALP3 inflammasome by alum crystals or
indirectly through release of the endogenous danger signal uric acid, which subsequently activates
NLRP3. - (answer) Question 4. Aluminum-containing vaccine adjuvants (alum) appear to mediate their
beneficial immunostimulatory effects through which of the following molecules of the innate immune
system?
A. TLR1/6 heterodimers
B. nucleotide oligomerization domain-like receptor family,
, JACI PRIMER EXAM 2023-2024 ACTUAL EXAM 120 QUESTIONS AND CORRECT DETAILED ANSWERS
pyrin domain-containing 3 (NLRP3, also called NALP3
or cryopyrin)
C. myeloid differentiation primary response gene 88
(MyD88)
D. killer cell immunoglobulin-like receptor (KIR)
1. Answer: C
Explanation: T-cell receptor activation leads to release of intracellular calcium stores, as well as influx of
extracellular calcium. Mature T cells express either CD4 or CD8 but not both. CD8 serves as a coreceptor
for MHC class I and not MHC class II molecules. The newborn screening for severe combined
immunodeficiency is performed by means of PCR quantitation of T-cell receptor excision circles on blood
spots. - (answer) Question 1. Which of the following statements concerning T cells is true?
A. On full maturation, T cells exiting the thymus express both CD4 and CD8.
B. CD8 serves as a coreceptor by binding to nonpolymorphic domains on MHC class II molecules.
C. T-cell activation leads both to release of intracellular calcium stores and to influx of extracellular
calcium.
D. Newborn screening for severe combined immunodeficiency is performed by counting T cells on a
blood spot.
2. Answer: D
Explanation: Natural killer T cells express markers of both T (ab) and natural killer (CD56) cells. CD251
regulatory T cells express forkhead box protein 3. RORgt is present in TH17 cells, which arise under the
influence of IL-6 and TGF-b. Target cell killing by cy- tolytic T lymphocytes is complement independent
and involves perforin, granzymes, and Fas-mediated apoptotic mechanisms. - (answer) Question 2.
Which of the following statements concerning ef- fector T cells is true?
A. CD251 regulatory T cells express the transcription factor retinoic acid receptor related orphan
receptor gt (RORgt).
B. TH17 cells arise from TH0 precursors under the influence
of IL-4 and IFN-g.
C. Killing of virally infected target cells by cytolytic T
lymphocytes is mediated by complement.
D. Natural killer T cells express abT-cell receptors and CD56.
