APCs use two major “billboards” to display peptide fragments. Which are they?
A. IgM and IgG
B. C3b and C5b
C. Class I and II MHC
D. CD40 and CD40L

C. Class I and II MHC

Class I MHC has what type of peptide-binding groove?
A. Open at both ends
B. Open at one end
C. Closed at both ends
D. Closed in the middle

C. Closed at both ends

Class II MHC has what type of peptide-binding groove?
A. Open at both ends
B. Closed at both ends
C. Open at one end
D. No binding groove

A. Open at both ends

Because class I MHC has a closed groove, what peptide length fits best?
A. 3–5 amino acids
B. 8–9 amino acids
C. 13–25 amino acids
D. 30–40 amino acids

B. 8–9 amino acids

Because class II MHC has an open groove, what peptide length can it fit?
A. 4–6 amino acids
B. 8–9 amino acids
C. 10–12 amino acids
D. 13–25 amino acids

D. 13–25 amino acids

Every human has three genes encoding class I HLA proteins. Which set is correct?
A. HLA-A, HLA-B, HLA-C
B. HLA-D, HLA-E, HLA-F
C. HLA-I, HLA-II, HLA-III
D. HLA-M, HLA-N, HLA-O

A. HLA-A, HLA-B, HLA-C

The class I HLA genes are located on which chromosome?
A. Chromosome 2
B. Chromosome 14
C. Chromosome 6
D. Chromosome 22

C. Chromosome 6

Each class I HLA protein pairs with which protein?
A. β2-microglobulin
B. TAP 1
C. TAP 2
D. Proteasome

A. β2-microglobulin

HLA protein plus β2-microglobulin forms a complete what?
A. Class II MHC
B. Complement receptor
C. Class I MHC
D. B-cell receptor

C. Class I MHC

Humans have the same gene for which class I partner protein?
A. HLA-A
B. HLA-B
C. HLA-C
D. β2-microglobulin

D. β2-microglobulin

Class I HLA genes are best described as what?
A. Highly polymorphic
B. Mostly identical
C. Antibody-dependent
D. Cytokine-encoded

A. Highly polymorphic

Class I MHC is selective about amino acids located where?
A. Peptide ends
B. Peptide middle
C. Fc region
D. C-terminal only

A. Peptide ends

Class I MHC is relatively “promiscuous” about amino acids located where?
A. Peptide ends
B. Peptide middle
C. TAP pore
D. β2 chain

B. Peptide middle

Class I MHC selectivity at peptide ends helps each peptide fit what?
A. TAP transporter
B. Binding groove ends
C. Proteasome core
D. Class II groove

B. Binding groove ends

Class II MHC molecules are encoded by which HLA region?
A. HLA-A region
B. HLA-B region
C. HLA-D region
D. HLA-C region

C. HLA-D region

The HLA-D region is located on which chromosome?
A. Chromosome 6
B. Chromosome 2
C. Chromosome 14
D. Chromosome 22

A. Chromosome 6

Compared with class I, class II MHC has selective binding points located where?
A. Only at ends
B. Along the groove
C. Only on β2-microglobulin
D. Outside the groove

B. Along the groove

MHC I molecules display what material?
A. Fragments of proteins
B. Whole antibodies
C. Intact bacteria
D. Free carbohydrates

A. Fragments of proteins

Endogenous proteins are proteins made by which source?
A. Nearby bacteria
B. Helper T cells
C. The cell itself
D. Extracellular fluid

C. The cell itself

Almost every nucleated cell expresses which MHC class?
A. Class II MHC
B. Class III MHC
C. Class I MHC
D. Secreted MHC

C. Class I MHC

Class I MHC molecules are inspected mainly by which cells?
A. Helper T cells
B. Plasma cells
C. B cells
D. Killer T cells

D. Killer T cells

Killer T cells are also called what?
A. Plasma lymphocytes
B. Cytotoxic lymphocytes
C. Regulatory lymphocytes
D. Follicular lymphocytes

B. Cytotoxic lymphocytes

Cytotoxic T lymphocytes inspect class I MHC mainly to determine whether a cell is what?
A. Infected
B. Opsonized
C. Allergic
D. Complement-coated

A. Infected

Approximately how many class I MHC molecules are on each cell?
A. 100,000
B. 1,000
C. 10 million
D. 60

A. 100,000

Class I MHC molecules on a cell are replaced how often?
A. Hourly
B. Weekly
C. Daily
D. Monthly

C. Daily

Old or defective intracellular proteins are broken down by what?
A. Lysosomes
B. Ribosomes
C. Golgi bodies
D. Proteasomes

D. Proteasomes

Protein fragments for class I loading are transported into which organelle?
A. Nucleus
B. Endoplasmic reticulum
C. Mitochondrion
D. Lysosome

B. Endoplasmic reticulum

Which transporters carry fragments into the ER?
A. HLA-A and HLA-B
B. C1 and C3
C. Igα and Igβ
D. TAP 1 and TAP 2

D. TAP 1 and TAP 2

Where are class I MHC molecules loaded with protein fragments?
A. Golgi apparatus
B. Phagolysosome
C. Endoplasmic reticulum
D. Cell membrane

C. Endoplasmic reticulum

Some macrophages cut proteins into segments specifically for which transporters?
A. HLA transporters
B. C1 transporters
C. CD40 transporters
D. TAP transporters

D. TAP transporters

Macrophages can process proteins specifically for TAP and which molecule?
A. Class II MHC
B. β2-microglobulin alone
C. Class I MHC
D. Complement receptors

C. Class I MHC

A viral protein is synthesized inside an epithelial cell. Which MHC class displays its fragments?
A. Class II MHC
B. Secretory IgA
C. Complement C3
D. Class I MHC

D. Class I MHC

A bacterial protein is engulfed by an APC from outside the cell. Which MHC class is generally suited for longer peptides?
A. Class I MHC
B. Class II MHC
C. β2-microglobulin
D. TAP complex

B. Class II MHC

Which statement about β2-microglobulin is correct?
A. It encodes HLA-D
B. It binds class II only
C. It forms TAP pores
D. Humans share its gene

D. Humans share its gene

Class II MHC differs from class I because its selective binding points are where?
A. Only at peptide ends
B. Only on β2-microglobulin
C. Only outside the groove
D. Spaced along the groove

D. Spaced along the groove

A class I peptide must fit tightly at the groove ends. What explains this?
A. Closed binding groove
B. Open binding groove
C. HLA-D encoding
D. C1 binding

A. Closed binding groove

A class II peptide can extend beyond the groove. What explains this?
A. β2-microglobulin pairing
B. TAP transport
C. HLA-C polymorphism
D. Open binding groove

D. Open binding groove

Which molecule is required to complete a class I MHC molecule?
A. C3b
B. CD40L
C. β2-microglobulin
D. Igβ

C. β2-microglobulin

Which molecule is not encoded by polymorphic class I HLA genes?
A. β2-microglobulin
B. HLA-A
C. HLA-B
D. HLA-C

A. β2-microglobulin

Which sequence best fits MHC I loading?
A. ER → proteasome → TAP
B. Proteasome → TAP → ER
C. TAP → lysosome → CD40
D. C1 → TAP → membrane

B. Proteasome → TAP → ER

A macrophage receives a cytokine signal that changes its proteasome composition for better MHC I presentation. Which cytokine caused this?
A. IL-4
B. TNF
C. IL-10
D. IFN-γ

D. IFN-γ

IFN-γ upregulates which proteasome-associated components?
A. LMP2, LMP7, MECL1
B. TAP1, TAP2, CLIP
C. B7, CD28, CD40
D. HLA-A, HLA-B, C1

A. LMP2, LMP7, MECL1

LMP2, LMP7, and MECL1 fit into which structure?
A. Endosomes
B. Phagosomes
C. Proteasomes
D. Ribosomes

C. Proteasomes

IFN-γ-modified proteasomes preferentially cut proteins after which amino acids?
A. Acidic or polar
B. Hydrophobic or basic
C. Aromatic or acidic
D. Neutral or sulfur-containing

B. Hydrophobic or basic

Proteasomes cut after hydrophobic/basic residues because TAP and MHC I favor these where?
A. Peptide C-termini
B. Peptide N-termini
C. MHC II grooves
D. Invariant chains

A. Peptide C-termini

TAP transporters preferentially bind peptides of what length?
A. 3–5 amino acids
B. 6–7 amino acids
C. 20–30 amino acids
D. 8–16 amino acids

D. 8–16 amino acids

Most proteins degraded by proteasomes are best described as what?
A. Extracellular proteins
B. Structurally flawed proteins
C. Complement-coated proteins
D. Antibody-bound proteins

B. Structurally flawed proteins

Proteasomal degradation usually targets flawed proteins more than simply what?
A. Viral
B. Exogenous
C. Old
D. Secreted

C. Old

Class II MHC molecules are expressed exclusively on which cells?
A. Red blood cells
B. Immune system cells
C. Skeletal muscle cells
D. Endothelial cells only

B. Immune system cells

Class II MHC molecules are designed to present antigen to which cells?
A. Helper T cells
B. Killer T cells
C. Natural killer cells
D. Plasma B cells

A. Helper T cells

Class II MHC molecules are made from which two protein chains?
A. Heavy and light
B. CD40 and CD40L
C. TAP1 and TAP2
D. α and β

D. α and β

In the ER, class II MHC α and β chains bind which third protein?
A. CLIP
B. HLA-DM
C. Invariant chain
D. β2-microglobulin

C. Invariant chain

Class II MHC binds the invariant chain in which organelle?
A. Endoplasmic reticulum
B. Golgi stack
C. Endosome
D. Phagosome

A. Endoplasmic reticulum

The invariant chain prevents premature peptide loading by sitting in the MHC II what?
A. Tail
B. Membrane anchor
C. Groove
D. Cytosolic domain

C. Groove

Why does the invariant chain occupy the MHC II groove?
A. It binds CD28
B. It blocks ER peptides
C. It activates C1
D. It degrades TAP

B. It blocks ER peptides

The invariant chain helps guide MHC II molecules through which structure?
A. Nucleus
B. Proteasome
C. Mitochondrion
D. Golgi stack

D. Golgi stack

After the Golgi, invariant-chain-bound MHC II is guided to which vesicles?
A. Lysosomes
B. Ribosomes
C. Endosomes
D. Peroxisomes

C. Endosomes

The goal of MHC II presentation is to display which proteins?
A. Endogenous proteins
B. Exogenous proteins
C. Structurally flawed proteins
D. Cytosolic proteins

B. Exogenous proteins

Exogenous proteins are best defined as proteins from where?
A. Outside the cell
B. Inside the nucleus
C. Proteasome fragments
D. Mitochondrial matrix

A. Outside the cell

Once inside an endosome, MHC II merges with what structure?
A. Proteasome
B. Ribosome
C. Golgi vesicle
D. Phagosome

D. Phagosome

The phagosome carries what material into the MHC II-loading pathway?
A. TAP transporters
B. Outside protein debris
C. β2-microglobulin
D. CD28 molecules

B. Outside protein debris

Inside the endosome, exogenous proteins are what?
A. Secreted intact
B. Sent to TAP
C. Bound by C1
D. Broken down

D. Broken down

During endosomal processing, most invariant chain is destroyed except what piece?
A. CLIP
B. TAP1
C. B7
D. LMP7

A. CLIP

CLIP remains temporarily in the MHC II groove to do what?
A. Bind CD28
B. Activate proteasomes
C. Guard the groove
D. Recruit NK cells

C. Guard the groove

Which protein releases CLIP from MHC II?
A. IFN-γ
B. TAP2
C. β2-microglobulin
D. HLA-DM

D. HLA-DM

HLA-DM release of CLIP allows loading of what?
A. Endogenous peptide
B. Exogenous protein fragment
C. Whole bacterium
D. C1 complex

B. Exogenous protein fragment

HLA-DM also helps ensure MHC II presents peptides that fit how?
A. Loosely
B. Randomly
C. Tightly
D. Weakly

C. Tightly

HLA-DM competes with peptides trying to bind which molecule?
A. MHC II
B. MHC I
C. CD28
D. TAP1

A. MHC II

HLA-DM acts like a peptide editor by favoring what?
A. Fastest peptides
B. Largest proteins
C. Tightest binders
D. Complement fragments

C. Tightest binders

For T cells to function, they need cognate antigen plus what?
A. Complement fixation
B. Antibody secretion
C. TAP transport
D. Co-stimulation

D. Co-stimulation

Killer T cells and helper T cells both require antigen presented by what?
A. MHC molecules
B. Antibodies
C. Complement proteins
D. Fc receptors

A. MHC molecules

Which cells have both class I and class II MHC and provide co-stimulation?
A. Neutrophils
B. APCs
C. Red blood cells
D. Platelets

B. APCs

Co-stimulation usually involves B7 on which cell?
A. T cell
B. NK cell
C. APC
D. Plasma cell

C. APC

Co-stimulation usually involves CD28 on which cell?
A. T cell
B. APC
C. Macrophage
D. Bacterium

A. T cell

A T cell recognizes antigen-MHC but receives no co-stimulation. What key signal is missing?
A. Antigen signal
B. TAP signal
C. CLIP signal
D. B7-CD28 signal

D. B7-CD28 signal

The MHC II pathway begins with α, β, and invariant chain assembly where?
A. Endosome
B. ER
C. Phagosome
D. Cell surface

B. ER

Invariant chain first blocks which event?
A. Peptide binding in ER
B. MHC II synthesis
C. Golgi transport
D. Endosomal fusion

A. Peptide binding in ER

Which sequence best fits MHC II loading?
A. Proteasome → TAP → ER
B. C1 → C3 → C5
C. CD28 → B7 → CLIP
D. ER → Golgi → endosome

D. ER → Golgi → endosome

A macrophage presents extracellular bacterial fragments to helper T cells. Which pathway is used?
A. MHC II pathway
B. MHC I pathway
C. NK-cell pathway
D. Complement pathway

A. MHC II pathway

A macrophage processes cytosolic proteins for killer T-cell inspection. Which pathway is emphasized?
A. MHC II pathway
B. MHC I pathway
C. IgE pathway
D. C1 pathway

B. MHC I pathway

IFN-γ-induced LMP proteins help generate peptides suited for which transporters?
A. HLA-DM
B. B7
C. TAP
D. CD28

C. TAP

IFN-γ-induced proteasome changes help generate peptides suited for which MHC class?
A. MHC II
B. Secretory IgA
C. Complement C1
D. MHC I

D. MHC I

TAP favors peptides with hydrophobic/basic features at which end?
A. N-terminus
B. C-terminus
C. Middle only
D. Both ends equally

B. C-terminus

MHC I favors hydrophobic/basic features at which end?
A. C-terminus
B. N-terminus
C. CLIP region
D. Invariant chain

A. C-terminus

Which statement best describes immunoproteasome-style cutting?
A. Cuts after acidic residues
B. Prevents all degradation
C. Generates MHC II peptides
D. Favors TAP-compatible peptides

D. Favors TAP-compatible peptides

An APC has both MHC classes and B7. What can it provide to T cells?
A. Antibody secretion
B. Complement fixation
C. Co-stimulation
D. IgA transport

C. Co-stimulation

Which set correctly lists the three main APC types?
A. Neutrophils, eosinophils, basophils
B. NK cells, mast cells, platelets
C. Dendritic cells, macrophages, B cells
D. Erythrocytes, monocytes, plasma cells

C. Dendritic cells, macrophages, B cells

For a macrophage to function well as an APC, it must usually be what?
A. Activated
B. Resting
C. Degranulated
D. Anucleate

A. Activated

Which B-cell state can function as an APC?
A. Immature B cell
B. Virgin B cell only
C. Plasma cell only
D. Activated B cell

D. Activated B cell

Dendritic cells are classically described as having what shape?
A. Spherical
B. Starfish-like
C. Spindle-shaped
D. Biconcave

B. Starfish-like

Dendritic cells should not be confused with which cell type?
A. Plasmacytoid dendritic cells
B. Activated macrophages
C. Activated B cells
D. Virgin T cells

A. Plasmacytoid dendritic cells

A dendritic cell migrates to a lymph node and activates a never-before-stimulated T cell. Which T cell is this?
A. Experienced T cell
B. Memory T cell
C. Virgin T cell
D. Regulatory T cell

C. Virgin T cell

Which APC is especially important for initiating immune responses?
A. Activated B cell
B. Dendritic cell
C. Activated macrophage
D. Plasma cell

B. Dendritic cell

Resting dendritic cells act as sentinel cells beneath which barrier?
A. Endothelial cells
B. Synovial cells
C. Red pulp
D. Epithelial cells

D. Epithelial cells

Resting dendritic cells beneath epithelial barriers are best described as what?
A. Antibody factories
B. Sentinel cells
C. Cytotoxic lymphocytes
D. Complement proteins

B. Sentinel cells

Resting dendritic cells store many reserve molecules of which class?
A. Class I MHC
B. IgG
C. CD1
D. Class II MHC

D. Class II MHC

Upon activation, reserve class II MHC molecules are loaded with what?
A. Surrounding antigens
B. Nuclear DNA only
C. Complement inhibitors
D. IgE antibodies

A. Surrounding antigens

A dendritic cell loads nearby antigens as it activates. This is like taking what?
A. Blood sample
B. Complement pulse
C. Local snapshot
D. Thymic census

C. Local snapshot

After activation, dendritic cells upregulate production of which class?
A. Class II MHC
B. CD1
C. IgA
D. Class I MHC

D. Class I MHC

Once activated, a dendritic cell travels through which system?
A. Bloodstream
B. Lymph system
C. Portal circulation
D. Biliary system

B. Lymph system

Activated dendritic cells increase production of which co-stimulatory protein?
A. CD40
B. CD28
C. B7
D. Fas

C. B7

The activated dendritic cell’s destination is usually which site?
A. Lymph node
B. Bone marrow
C. Thymic cortex
D. Spleen capsule

A. Lymph node

By the time an activated dendritic cell reaches a lymph node, it can activate which cells?
A. Naive B cells only
B. Virgin T cells
C. Erythrocytes
D. Neutrophils

B. Virgin T cells

How long does an activated dendritic cell live after reaching a lymph node?
A. About 1 week
B. About 1 day
C. About 1 month
D. About 1 year

A. About 1 week

As activated dendritic cells leave tissues, they produce what signaling molecules?
A. Antibodies
B. Complement pores
C. Histamine granules
D. Chemokines

D. Chemokines

Dendritic-cell chemokines recruit which cells into tissues?
A. Plasma cells
B. Erythrocytes
C. Monocytes
D. Platelets

C. Monocytes

Recruited monocytes can enter tissues and become which cells?
A. Dendritic cells
B. Eosinophils
C. Mast cells
D. Plasma cells

A. Dendritic cells

Why do activated dendritic cells recruit monocytes as replacements?
A. To kill antibodies
B. To remove lymph nodes
C. To stop antigen capture
D. To obtain fresh snapshots

D. To obtain fresh snapshots

Dendritic antigen-presenting cells generally do not what?
A. Present antigen
B. Express MHC
C. Activate T cells
D. Kill

D. Kill

Which APC distinction is correct?
A. Dendritic cells kill
B. Macrophages do not travel
C. B cells lack receptors
D. APCs lack MHC

B. Macrophages do not travel

Activated macrophages mainly provide consistent restimulation of which T cells?
A. Virgin T cells
B. Naive T cells
C. Experienced T cells
D. Immature T cells

C. Experienced T cells

Activated macrophages restimulate T cells mainly at what location?
A. Bone marrow
B. Site of infection
C. Thymic cortex
D. Blood plasma

B. Site of infection

Which APC has an advantage in concentrating antigen?
A. Activated B cell
B. Activated macrophage
C. Dendritic cell
D. NK cell

A. Activated B cell

Activated B cells can concentrate antigen using which receptor?
A. T-cell receptor
B. B-cell receptor
C. CD1 receptor
D. Fas receptor

B. B-cell receptor

Experienced B cells act as APCs specifically for which T cells?
A. Killer T cells
B. Regulatory T cells
C. NK cells
D. Helper T cells

D. Helper T cells

When antigen is scarce, experienced B cells are better at activating which cells?
A. Killer T cells
B. Helper T cells
C. Macrophages
D. Neutrophils

B. Helper T cells

Which APC is especially useful when little antigen is present?
A. Dendritic cell
B. Neutrophil
C. Experienced B cell
D. Eosinophil

C. Experienced B cell

Some APCs present exogenous antigen on class I MHC. What is this called?
A. Class switching
B. Cross-presentation
C. Affinity maturation
D. Polyclonal activation

B. Cross-presentation

Cross-presentation uses exogenous antigens for which MHC class?
A. Class II only
B. CD1 only
C. Secretory IgA
D. Class I MHC

D. Class I MHC

Cross-presentation is especially important because exogenous antigens can activate which cells?
A. Plasma cells
B. Mast cells
C. Killer T cells
D. Erythrocytes

C. Killer T cells

The nonclassical MHC family that binds lipids is called what?
A. CD1
B. CD28
C. CD40
D. C1

A. CD1

CD1 proteins are structurally similar to MHC I because they include what?
A. Two equal chains
B. Invariant chain only
C. Long heavy chain
D. Antibody light chain

C. Long heavy chain

CD1 proteins pair with which molecule?
A. CD40L
B. β2-microglobulin
C. CLIP
D. C3b

B. β2-microglobulin

CD1 grooves are designed to bind what?
A. Peptides
B. DNA
C. Carbohydrates
D. Lipids

D. Lipids

Organ transplant rejection is primarily caused by recognition of what?
A. MHC molecules
B. IgA molecules
C. C1 inhibitors
D. Histamine

A. MHC molecules

Which APC is most associated with taking tissue “snapshots”?
A. Dendritic cell
B. Activated macrophage
C. Activated B cell
D. NK cell

A. Dendritic cell

Resting dendritic cells load reserve class II MHC molecules when they become what?
A. Degranulated
B. Activated
C. Apoptotic
D. Anucleate

B. Activated

Activated dendritic cells travel to lymph nodes through lymph because they are trying to find what?
A. Red blood cells
B. Platelets
C. Antibodies only
D. Virgin T cells

D. Virgin T cells

A cell takes up extracellular antigen but displays it on MHC I. Which process occurred?
A. Cross-presentation
B. Class switching
C. Complement fixation
D. ADCC

A. Cross-presentation

CD1 proteins are part of which MHC family?
A. Classical MHC
B. Antibody MHC
C. Nonclassical MHC
D. Complement MHC

C. Nonclassical MHC