Biomed 3

TCR gene rearrangement ensures: A. Limited receptor diversity B. A variety of antigen specificities C. No recognition of self-antigens D. Expression of B cell receptors

B. A variety of antigen specificities

Clonal selection and expansion refers to: A. Random destruction of T cells B. Proliferation of activated lymphocytes C. Removal of memory cells D. Downregulation of IL-2 receptors

B. Proliferation of activated lymphocytes

Which sequence correctly describes T cell maturation? A. SP → DP → DN B. DP → DN → SP C. DN → DP → SP D. DN → SP → DP

C. DN → DP → SP

What occurs during the DN stage? A. Negative selection B. Rearranging TCR and forming the pre-TCR C. Expression of both CD4 and CD8 D. Commitment to CD4 lineage

B. Rearranging TCR and forming the pre-TCR

What occurs during the DP stage? A. Pre-TCR formation B. Negative selection only C. TCR rearrangement, formation of functional TCR, and positive selection D. Exit to periphery

C. TCR rearrangement, formation of functional TCR, and positive selection

What is the main event during the SP stage? A. Formation of the pre-TCR B. Positive selection C. Establishing central tolerance via negative selection D. Expression of both CD4 and CD8

C. Establishing central tolerance via negative selection

DN thymocytes rearrange which loci? A. Beta, alpha, and delta TCR loci B. Gamma only C. Heavy and light chain loci D. CD28 loci

A. Beta, alpha, and delta TCR loci

What happens if the beta chain rearranges before alpha and delta? A. The cell dies B. A pre-TCR forms → DP thymocyte + proliferation C. The cell becomes SP D. CD28 expression is suppressed

B. A pre-TCR forms → DP thymocyte + proliferation

Expression of a functional TCR leads to what phenotype? A. CD4 only B. CD8 only C. DN D. DP

D. DP

DP thymocytes undergo: A. Negative selection B. Pre-TCR formation C. Positive selection D. Apoptosis only

C. Positive selection

The strength/type of TCR interaction during positive selection determines: A. Th1 vs Th2 fate B. CD4 vs CD8 lineage C. IL-2 receptor affinity D. AIRE expression

B. CD4 vs CD8 lineage

During negative selection, SP thymocytes migrate to: A. Thymic cortex B. Lymph nodes C. Thymic medulla D. Bone marrow

C. Thymic medulla

In negative selection, TCRs that bind too tightly to self-antigens: A. Become memory cells B. Become Tregs C. Are signaled to die D. Migrate to lymph nodes

C. Are signaled to die

In negative selection, moderate binding of TCR to self-antigen results in: A. Apoptosis B. Survival C. Anergy D. Exhaustion

B. Survival

AIRE's main function is to: A. Promote CD4 lineage B. Activate dendritic cells C. Allow expression of peripheral antigens in the thymus D. Increase TCR diversity

C. Allow expression of peripheral antigens in the thymus

Immature T cells that strongly interact with self-antigen will undergo: A. Proliferation B. Activation C. Apoptosis D. Differentiation into Tregs

C. Apoptosis

During the DN (rearrangement) thymocyte development stage, what critical event occurs? A. Rearranging TCR(beta) B. Expression of both CD4 and CD8 C. Negative selection against high self-affinity TCR D. Lineage commitment to CD4 T cell

A. Rearranging TCR(beta)

What determines whether a positively selected DP thymocyte becomes a CD4 or CD8 T cell? A. Strength of TCR signal B. Type of MHC molecule recognized C. Presence of IL-2 D. Expression of AIRE

B. Type of MHC molecule recognized

Anergy results from lack of B7 expression and engagement of CTLA-4, leading to: A. Full activation B. Memory formation C. Functional unresponsiveness D. Increased cytokine secretion

C. Functional unresponsiveness

Regulatory T cells (Tregs) produce: A. Only IL-2 B. Anti-inflammatory/immunosuppressive cytokines C. Histamine D. Perforin only

B. Anti-inflammatory/immunosuppressive cytokines

Tregs interact with immune cells to: A. Promote activation B. Enhance antigen presentation C. Inhibit activation D. Increase IL-12 release

C. Inhibit activation

Tregs release granzyme and perforin to: A. Activate neutrophils B. Kill T effector cells C. Promote B cell maturation D. Activate macrophages

B. Kill T effector cells

Which of the following accurately describes a mechanism of peripheral T-cell tolerance? A. Positive selection in the thymic cortex B. Negative selection in the thymic medulla C. Anergy induced by lost costimulation signal D. Expression of AIRE transcription factor

C. Anergy induced by lost costimulation signal

T cell activation involves which sequence? A. ZAP-70 activates Lck B. CD4/CD8 bring Lck → Lck activates ZAP-70 → downstream signaling C. AIRE activates ZAP-70 D. IL-10 activates Lck

B. CD4/CD8 bring Lck → Lck activates ZAP-70 → downstream signaling

T cell activation induces production of: A. Only IL-4 B. IL-2 and an additional IL-2 receptor subunit C. TNF-α only D. IgM

B. IL-2 and an additional IL-2 receptor subunit

IL-2 binding to high-affinity IL-2R causes: A. Apoptosis B. T cell proliferation C. Loss of costimulation D. Downregulation of TCR

B. T cell proliferation

Activated T cells differentiate into: A. Neutrophils B. Th and Tc effector cells C. NK cells only D. Basophils

B. Th and Tc effector cells

Naive CD4 T cells differentiate into Th1, Th2, or Treg depending on: A. MHC type B. Cytokine environment C. Antibody isotype D. Location in spleen

B. Cytokine environment

Th2 cells primarily: A. Kill infected cells B. Neutralize pathogens C. Present antigens D. Activate complement

B. Neutralize pathogens

Naive CD8 T cells can be activated directly by: A. Neutrophils B. Tregs C. Virus-infected dendritic cells D. B cells

C. Virus-infected dendritic cells

Activated CD8 T cells secrete IL-2 to: A. Activate macrophages B. Promote their own proliferation C. Kill neutrophils D. Suppress dendritic cells

B. Promote their own proliferation

Cytotoxic T lymphocytes (CTLs) kill target cells by: A. Complement proteins B. Antibody-mediated lysis C. Perforin and granzyme delivery D. IL-4 secretion

C. Perforin and granzyme delivery

Naive CD8 T cell activation requires direct interaction with: A. B cells B. Virus-infected DC C. NK cells D. Basophils

B. Virus-infected DC

T helper cells help improve APC costimulation by inducing expression of: A. CD28 B. B7 C. IL-12 D. MHC I

B. B7

Th cells secrete IL-2, which acts on neighboring CD8 T cells by: A. Lowering TCR affinity B. Binding high-affinity IL-2R C. Blocking co-stimulation D. Decreasing proliferation

B. Binding high-affinity IL-2R

Which of the following best describes the role of T helper cells in immune responses? A. Promotion of dendritic cell recruitment via IL-12 B. Induction of neutrophil recruitment via IL-17 C. Activation of cytotoxic T lymphocytes via IL-2 D. Activation of regulatory T cells via IL-10

C. Activation of cytotoxic T lymphocytes via IL-2

Activated CD8 Tc cells kill targets presenting: A. Antigen on MHC II B. Lipids on CD1 C. Peptide on MHC I D. Carbohydrates on BCR

C. Peptide on MHC I

Activated CD4 Th1/Th2 cells recognize antigen presented by: A. Neutrophils B. RBCs C. APCs and activate them D. Fibroblasts

C. APCs and activate them

Upon antigen recognition, CTLs reorganize their cytoskeleton by moving: A. Lysosomes toward nucleus B. MTOC and Golgi toward the target cell interface C. CD28 receptors into the ER D. MHC II molecules to the surface

B. MTOC and Golgi toward the target cell interface

Which subset is correctly matched with its function? A. Helper T cells – kill virus-infected cells B. Cytotoxic T cells – kill virus-infected cells C. Plasma cells – activate macrophages D. NK cells – present antigen to T cells

B. Cytotoxic T cells – kill virus-infected cells