A naive lymphocyte first recognizes its specific antigen and begins adaptive immune activation. Where does this recognition phase occur?
A. Primary lymphoid organs
B. Secondary lymphoid organs
C. Peripheral infected tissue
D. Bone marrow sinusoids

B. Secondary lymphoid organs

Which set contains only secondary lymphoid organs?
A. Thymus, spleen, MALT
B. Bone marrow, thymus, spleen
C. Lymph nodes, thymus, MALT
D. Lymph nodes, spleen, MALT

D. Lymph nodes, spleen, MALT

Which organs are classified as primary lymphoid organs?
A. Bone marrow and thymus
B. Spleen and thymus
C. Lymph nodes and MALT
D. Cortex and paracortex

A. Bone marrow and thymus

A patient has impaired lymphoid follicle formation. Which immune structures would most directly share this abnormality?
A. Primary lymphoid organs
B. All lymphatic vessels
C. Secondary lymphoid organs
D. All inflamed tissues

C. Secondary lymphoid organs

The common anatomical structure shared by secondary lymphoid organs is which of the following?
A. High endothelial venules
B. Lymphoid follicles
C. Hassall corpuscles
D. Red pulp cords

B. Lymphoid follicles

Lymphoid follicles begin as loose networks of which cell type?
A. Conventional dendritic cells
B. Medullary epithelial cells
C. Paracortical macrophages
D. Follicular dendritic cells

D. Follicular dendritic cells

Early lymphoid follicles form in regions especially rich in which lymphocyte population?
A. B cells
B. T cells
C. NK cells
D. Plasma cells

A. B cells

Follicular dendritic cells are already present by which developmental period?
A. First trimester
B. Birth
C. Second trimester
D. Early infancy

C. Second trimester

Which cell type displays antigen primarily to B cells?
A. Macrophages
B. Follicular dendritic cells
C. Conventional dendritic APCs
D. Thymic epithelial cells

B. Follicular dendritic cells

Which cell type presents antigen primarily to T cells?
A. Follicular dendritic cells
B. Conventional dendritic APCs
C. Marginal-zone B cells
D. Stromal reticular cells

B. Conventional dendritic APCs

A follicular dendritic cell binds antigen coated with complement fragments. Which receptor function explains this?
A. BCR crosslinking receptors
B. Complement fragment binding
C. TCR antigen presentation
D. Fc-independent antigen uptake

B. Complement fragment binding

A follicular dendritic cell bind complement-opsonized antigen because they express receptors for which material?
A. Fc regions
B. Cytokine gradients
C. Complement fragments
D. Chemokine ligands

C. Complement fragments

A follicular dendritic cell holds many antigen molecules very close together. What B-cell event does this promote?
A. TCR editing
B. FasL signaling
C. BCR crosslinking
D. MHC I loading

C. BCR crosslinking

Follicular dendritic cells can also bind immune complexes using receptors for which antibody region?
A. Fab region
B. J chain
C. Variable region
D. Fc region

D. Fc region

A follicular dendritic cell attracts and activates B cells, leading to intense B-cell proliferation. Over time, this active follicle becomes what?
A. Red pulp
B. Germinal center
C. Thymic cortex
D. Paracortical cord

B. Germinal center

A germinal center is best described as which structure?
A. Active secondary lymphoid follicle
B. Primary lymphoid maturation site
C. T-cell deletion region
D. Macrophage-rich venous sinus

A. Active secondary lymphoid follicle

Before adaptive immunity responds effectively to infection, which system must first detect danger?
A. Humoral system
B. Complement system
C. Innate system
D. Lymphatic system

C. Innate system

B cells proliferating in germinal centers become fragile. Which cells rescue them from apoptosis?
A. Helper T cells
B. NK cells
C. Neutrophils
D. Follicular macrophages

A. Helper T cells

Which secondary lymphoid organ lacks high endothelial venules?
A. MALT
B. Lymph node
C. Peyer patch
D. Spleen

D. Spleen

High endothelial venules serve primarily as a doorway for which cells?
A. Neutrophils and eosinophils
B. B and T cells
C. Monocytes and basophils
D. Plasma cells and platelets

B. B and T cells

High endothelial venules allow lymphocytes to enter secondary lymphoid organs from which compartment?
A. Blood
B. Bone marrow
C. Germinal centers
D. Efferent lymph

A. Blood

High endothelial venules are regions within which vessel type?
A. Arteriole
B. Capillary
C. Venule
D. Lymphatic duct

C. Venule

In a lymph node, high endothelial venules are located in which region?
A. Cortex
B. Medulla
C. Paracortex
D. Capsule

C. Paracortex

In a lymph node, B cells mainly accumulate in which area?
A. Paracortex
B. Cortex
C. Medulla
D. Hilum

B. Cortex

In a lymph node, T cells mainly accumulate in which area?
A. Paracortex
B. Cortex
C. Follicle center
D. Subcapsular sinus

A. Paracortex

Conventional dendritic cells mainly accumulate in which lymph-node region?
A. Cortex
B. Medulla
C. Paracortex
D. Germinal center

C. Paracortex

Follicular dendritic cells are mainly located in which lymph-node region?
A. Paracortex
B. Cortex
C. Medulla
D. Hilum

B. Cortex

In lymph nodes, the B-cell area correlates with which dendritic cell location?
A. Conventional DCs in cortex
B. FDCs in cortex
C. FDCs in paracortex
D. Macrophages in paracortex

B. FDCs in cortex

In lymph nodes, the T-cell area correlates with which dendritic cell location?
A. FDCs in medulla
B. Macrophages in cortex
C. Conventional DCs in paracortex
D. B cells in sinuses

C. Conventional DCs in paracortex

Lymph-node sinus walls are carpeted with which immune cells?
A. Dendritic cells
B. Macrophages
C. Plasma cells
D. Eosinophils

B. Macrophages

Movement of immune cells within secondary lymphoid organs is coordinated by which signal type?
A. Chemokines
B. Antibodies
C. Perforins
D. Integrins only

A. Chemokines

Chemokines are best described as which type of cytokine?
A. Apoptotic cytokines
B. Chemoattractive cytokines
C. Cytotoxic cytokines
D. Complement-fixing cytokines

B. Chemoattractive cytokines

Follicular dendritic cells produce which chemokine to attract naive B cells?
A. CCR7
B. ICOSL
C. CXCR5
D. CXCL13

D. CXCL13

After a B cell finds its cognate antigen, what happens to its CXCL13 receptor expression?
A. It increases sharply
B. It remains unchanged
C. It downregulates
D. It switches to CD28

C. It downregulates

After recognizing cognate antigen, an activated B cell upregulates which chemokine receptor?
A. CXCL13
B. CCR7
C. ICOSL
D. B7

B. CCR7

CCR7 expression helps activated B cells migrate toward which region?
A. Medullary sinus
B. Thymic cortex
C. Blood-red pulp border
D. Cortex-paracortex border

D. Cortex-paracortex border

The cortex-paracortex border is important because it allows meeting between which cells?
A. B cells and T cells
B. NK cells and neutrophils
C. Macrophages and eosinophils
D. Plasma cells and platelets

A. B cells and T cells

Activated helper T cells downregulate signals keeping them in which region?
A. Cortex
B. Paracortex
C. Medulla
D. Red pulp

B. Paracortex

Activated helper T cells upregulate which receptor to meet activated B cells?
A. CCR7
B. CXCL13
C. CXCR5
D. ICOSL

C. CXCR5

CXCR5 expression helps helper T cells congregate with activated B cells at which site?
A. Medullary cord
B. Follicle border
C. Splenic red pulp
D. Efferent lymphatic

B. Follicle border

B cells require help from activated helper T cells. Activated helper T cells also require help from which cells?
A. Activated B cells
B. Resting macrophages
C. Naive neutrophils
D. Medullary thymocytes

A. Activated B cells

The reciprocal help between activated B cells and activated Th cells occurs through what mechanism?
A. Cell-cell contact
B. Antibody secretion only
C. Complement lysis
D. Cytokine diffusion only

A. Cell-cell contact

Which B-cell surface protein binds CD28 on helper T cells?
A. CCR7
B. ICOSL
C. B7
D. CXCL13

C. B7

Which B-cell surface protein binds ICOS on helper T cells?
A. B7
B. ICOSL
C. CCR7
D. CXCR5

B. ICOSL

Which helper T-cell protein binds B7 on the activated B-cell surface?
A. ICOS
B. CD28
C. CCR7
D. CXCR5

B. CD28

Which helper T-cell protein binds ICOSL on the activated B-cell surface?
A. CD28
B. CXCL13
C. CCR7
D. ICOS

D. ICOS

A defect prevents activated B cells from interacting with Th-cell CD28. Which B-cell molecule is most likely defective?
A. B7
B. CCR7
C. ICOSL
D. CXCL13

A. B7

A defect prevents activated B cells from interacting with Th-cell ICOS. Which B-cell molecule is most likely defective?
A. CXCR5
B. ICOSL
C. B7
D. CCR7

B. ICOSL

A patient has impaired complement deposition on antigen. Which FDC function would be most directly reduced?
A. Binding opsonized antigen
B. Producing IL-2
C. Presenting peptide to T cells
D. Activating thymic selection

A. Binding opsonized antigen

Which statement best captures secondary lymphoid organ function?
A. They produce immature lymphocytes
B. They delete autoreactive thymocytes
C. They support antigen recognition
D. They generate hematopoietic stem cells

C. They support antigen recognition

At the follicle border, an activated Th cell directly helps an activated B cell through which ligand-receptor pair?
A. ICOSL–ICOS
B. B7–CD28
C. CD40L–CD40
D. CXCL13–CXCR5

C. CD40L–CD40

During the B-cell/Th-cell “dance,” which molecule is provided by the helper T cell?
A. CD40L
B. B7
C. ICOSL
D. Antigen

A. CD40L

During the B-cell/Th-cell “dance,” which molecule is found on the B-cell surface and binds CD40L?
A. ICOS
B. CD28
C. CXCR5
D. CD40

D. CD40

Activated B cells provide which material to help helper T cells mature?
A. IL-17, IL-21, IL-23
B. Antigen, B7, ICOSL
C. CD40L, IL-2, FasL
D. Perforin, granzyme, IFN-gamma

B. Antigen, B7, ICOSL

A helper T cell becomes fully mature at the follicular border after contact with an activated B cell. What is it now called?
A. Th0 cell
B. Treg cell
C. Tfh cell
D. CTL cell

C. Tfh cell

Follicular helper T cells are licensed to rescue which fragile cell population?
A. Germinal-center B cells
B. Naive T cells
C. Marginal-zone macrophages
D. Follicular dendritic cells

A. Germinal-center B cells

A germinal-center B cell receives Tfh help and avoids apoptosis. Which later processes can Tfh cells support?
A. Chemotaxis and phagocytosis
B. Class switching and hypermutation
C. Necrosis and opsonization
D. Tolerance and anergy

B. Class switching and hypermutation

During affinity maturation, B cells with higher-affinity receptors gain an advantage by doing what?
A. Secreting more IL-12
B. Plucking more antigen
C. Blocking CD40 signaling
D. Losing class II MHC

B. Plucking more antigen

Higher-affinity B cells present more antigen to Tfh cells using which molecule?
A. Class II MHC
B. Class I MHC
C. CD40 ligand
D. TLR4 receptor

A. Class II MHC

In germinal centers, greater antigen presentation by high-affinity B cells causes what outcome?
A. Less Tfh help
B. Immediate necrosis
C. More Tfh help
D. Reduced proliferation

C. More Tfh help

Somatic hypermutation selects higher-affinity B cells because these cells receive more help from which cells?
A. NK cells
B. Tfh cells
C. Neutrophils
D. Eosinophils

B. Tfh cells

A killer T cell recognizes cognate antigen presented by dendritic cells in a lymph node. Where does activation occur?
A. Cortex
B. Medulla
C. Follicle
D. Paracortex

D. Paracortex

A lymph node draining an infected wound becomes enlarged. Which process contributes most directly?
A. Lymphocyte proliferation
B. Erythrocyte trapping
C. Platelet aggregation
D. Fibroblast calcification

A. Lymphocyte proliferation

In infected draining lymph nodes, medullary sinuses may become clogged by which cells?
A. Basophils
B. Eosinophils
C. Macrophages
D. Mast cells

C. Macrophages

Peyer patches are examples of which lymphoid tissue?
A. Thymic tissue
B. Red pulp
C. Bone marrow
D. MALT

D. MALT

Unlike lymph nodes, Peyer patches lack which structure?
A. Outgoing lymphatics
B. Incoming lymphatics
C. Germinal centers
D. B-cell follicles

B. Incoming lymphatics

Peyer patches still contain which drainage structure?
A. Outgoing lymphatics
B. Incoming lymphatics
C. Splenic sinusoids
D. Afferent arterioles

A. Outgoing lymphatics

Peyer patches are topped by which specialized epithelial cells?
A. Goblet cells
B. Paneth cells
C. Enteroendocrine cells
D. M cells

D. M cells

M cells over Peyer patches are not coated with which structures?
A. IgE and CD40
B. B7 and ICOSL
C. Mucus and villi
D. FasL and perforin

C. Mucus and villi

M cells sample material from which location?
A. Splenic blood
B. Intestinal lumen
C. Bone marrow
D. Medullary sinus

B. Intestinal lumen

M cells transport sampled intestinal material into which site?
A. Bloodstream
B. Thymic medulla
C. Red pulp
D. Underlying tissues

D. Underlying tissues

The spleen primarily functions as what type of filter?
A. Blood filter
B. Lymph filter
C. Mucus filter
D. Airway filter

A. Blood filter

Approximately what fraction of cardiac output enters the spleen?
A. 1%
B. 20%
C. 5%
D. 50%

C. 5%

The spleen screens circulating blood approximately every how long?
A. 5 minutes
B. 30 minutes
C. 6 hours
D. 1 day

B. 30 minutes

Compared with lymph nodes and Peyer patches, the spleen is less selective because everything enters from where?
A. Blood
B. Lymph
C. Mucus
D. Thymus

A. Blood

Which organs are selective about where B/T cells and antigens enter?
A. Spleen and thymus
B. Marrow and thymus
C. Spleen and marrow
D. Lymph nodes and Peyer patches

D. Lymph nodes and Peyer patches

In the spleen, T cells are temporarily retained in which region?
A. Marginal sinus
B. Red pulp
C. PALS
D. Trabeculae

C. PALS

In the spleen, B cells are found between which structures?
A. Red pulp and capsule
B. PALS and marginal sinuses
C. Thymus and medulla
D. Cortex and paracortex

B. PALS and marginal sinuses

The periarteriolar lymphocyte sheath mainly retains which cells?
A. T cells
B. B cells
C. Plasma cells
D. Macrophages

A. T cells

The spleen lacks lymphatics to transport dendritic cells from tissues. How does it compensate?
A. Uses thymic epithelial cells
B. Uses incoming M cells
C. Uses circulating neutrophils
D. Uses resident dendritic cells

D. Uses resident dendritic cells

In the spleen, resident dendritic cells take up antigens from invaders located where?
A. Mucus layer
B. Lymphatic fluid
C. Blood
D. Thymic cortex

C. Blood

Which organ is a main site where B cells can activate without Th-cell assistance?
A. Lymph node
B. Spleen
C. Thymus
D. Bone marrow

B. Spleen

B cells that can activate without Th-cell help in the spleen are called what?
A. Germinal-center B cells
B. Naive follicular B cells
C. Plasma memory cells
D. Marginal-zone B cells

D. Marginal-zone B cells

Marginal-zone B cells are stationed where they contact blood entering the spleen. Where is this?
A. Marginal sinuses
B. Red pulp cords
C. Splenic capsule
D. Central arteriole wall

A. Marginal sinuses

Secondary lymphoid organs are strategically positioned to intercept which threat?
A. Self-reactive thymocytes
B. Aging erythrocytes only
C. Invaders entering the body
D. Bone marrow precursors

C. Invaders entering the body

Secondary lymphoid organs provide environments that mobilize weapons appropriate to what?
A. Thymocyte selection stage
B. Likely invading organisms
C. Red-cell deformability
D. Platelet activation status

B. Likely invading organisms

The most important function of secondary lymphoid organs is bringing together which cells?
A. Platelets and erythrocytes
B. Mast cells and basophils
C. Fibroblasts and osteoblasts
D. Lymphocytes and APCs

D. Lymphocytes and APCs

Bringing lymphocytes and APCs together increases the probability of activating which immune system?
A. Adaptive immune system
B. Complement system
C. Coagulation system
D. Innate barrier system

A. Adaptive immune system

The process of B and T cells moving to specific locations is called what?
A. Chemotactic drift
B. Lymphocyte trafficking
C. Germinal rescue
D. Antigen plucking

B. Lymphocyte trafficking

Virgin and experienced lymphocytes differ mainly in which feature?
A. Nuclear membrane number
B. Immunoglobulin shape
C. Traffic patterns
D. Ribosomal density

C. Traffic patterns

Virgin T cells use which molecule to enter lymph nodes through HEVs?
A. L-selectin
B. αEβ7
C. ICOSL
D. FasL

A. L-selectin

L-selectin on virgin T cells binds which ligand on lymph-node HEVs?
A. MadCAM-1
B. ICOS
C. CD40
D. GlyCAM-1

D. GlyCAM-1

Virgin T cells use which integrin to enter Peyer patches and intestinal lymph nodes?
A. CD28
B. α4β7
C. CXCL13
D. CD40L

B. α4β7

α4β7 on virgin T cells binds which ligand on intestinal HEVs?
A. GlyCAM-1
B. Fas receptor
C. MadCAM-1
D. ICOSL

C. MadCAM-1

MadCAM-1 is expressed on HEVs in which sites?
A. Peyer patches, intestinal nodes
B. Thymus, bone marrow
C. Red pulp, splenic capsule
D. Skin, hepatic sinusoids

A. Peyer patches, intestinal nodes

Virgin T cells circulate through blood and lymph, spending about how long per loop?
A. 1 day
B. 1 week
C. 6 weeks
D. 30 minutes

A. 1 day

If a virgin T cell does not find cognate antigen, it dies after approximately how long?
A. 1 day
B. 30 minutes
C. 1 year
D. 6 weeks

D. 6 weeks

A virgin T cell failing to find cognate antigen eventually dies by what mechanism?
A. Necrosis
B. Pyroptosis
C. Apoptosis
D. Complement lysis

C. Apoptosis

Experienced T cells that have found cognate antigen have their travel passports become what?
A. Expanded
B. Deleted
C. Randomized
D. Restricted

D. Restricted

Experienced T cells express adhesion molecules based on what location?
A. Where they activated
B. Where they die
C. Where they circulate randomly
D. Where antibodies bind

A. Where they activated

A T cell activated in a Peyer patch will increase which adhesion molecule?
A. GlyCAM-1
B. CD40
C. α4β7
D. B7

C. α4β7

Increased α4β7 on Peyer-patch-activated T cells helps them do what?
A. Return to mucosal sites
B. Enter thymic cortex
C. Bind splenic red pulp
D. Block dendritic migration

A. Return to mucosal sites

Experienced T cells also carry “combat passports” that help them enter what sites?
A. Primary lymphoid organs
B. Sites of infection
C. Bone marrow niches
D. Thymic medulla

B. Sites of infection

Experienced mucosa-activated T cells express which integrin?
A. α4β7
B. MadCAM-1
C. L-selectin
D. αEβ7

D. αEβ7

αEβ7 helps experienced mucosal T cells enter which tissue environment?
A. Inflamed mucosa
B. Splenic capsule
C. Thymic cortex
D. Bone marrow

A. Inflamed mucosa

A defect in CD40L expression on activated Th cells would most directly impair which interaction?
A. B-cell CD40 activation
B. HEV entry into nodes
C. Antigen plucking by FDCs
D. M-cell sampling

A. B-cell CD40 activation

A B cell fails to provide B7 and ICOSL to a helper T cell. Which process is most directly impaired?
A. CTL granzyme release
B. Helper T-cell maturation
C. M-cell antigen transport
D. Splenic blood screening

B. Helper T-cell maturation

A high-affinity B cell outcompetes low-affinity B cells in a germinal center. Which mechanism best explains this?
A. Less antigen presentation
B. Better antigen plucking
C. Loss of class II MHC
D. Reduced Tfh contact

B. Better antigen plucking

A patient’s draining lymph node is swollen after cellulitis. Which combined mechanism best explains the swelling?
A. Lymphocyte loss, neutrophil apoptosis
B. Platelet trapping, RBC hemolysis
C. Lymphocyte growth, macrophage clogging
D. Fibrosis, thymocyte expansion

A. Lymphocyte loss, neutrophil apoptosis

A virgin T cell enters intestinal lymphoid tissue. Which receptor-ligand pair is most likely used?
A. CD40L–CD40
B. L-selectin–GlyCAM-1
C. α4β7–MadCAM-1
D. ICOS–ICOSL

C. α4β7–MadCAM-1

A virgin T cell enters a nonintestinal lymph node through HEVs. Which pair is most relevant?
A. αEβ7–mucosal ligand
B. α4β7–MadCAM-1
C. ICOS–ICOSL
D. L-selectin–GlyCAM-1

D. L-selectin–GlyCAM-1

A mucosa-activated experienced T cell leaves the lymphoid organ. Which change best predicts its future homing?
A. More α4β7 expression
B. Loss of all integrins
C. More splenic PALS binding
D. Less tissue selectivity

A. More α4β7 expression