Question 1

Which of the following best describes the role of dendritic cells in the activation of naïve T cells within secondary lymphoid tissue?

Accepted Answer

They engulf pathogens, migrate to secondary lymphoid tissue, and present processed antigens on MHC molecules to naïve T cells.

Question 2

What is the primary function of interleukin-2 (IL-2) in T-cell activation?

Accepted Answer

IL-2 promotes division and clonal expansion of activated T cells.

Question 3

During antigen presentation, which molecule on the antigen-presenting cell provides the costimulatory signal required for naïve T-cell activation?

Accepted Answer

B7

Question 4

A patient with a genetic defect in the CD3 complex of T cells would most likely have impaired:

Accepted Answer

Signal transduction following T-cell receptor engagement

Question 5

Which process is essential for T cells to migrate into secondary lymphoid tissue from the circulation?

Accepted Answer

Expression of CCR7 on T cells and binding to CCL21 chemokine in lymphoid tissue

Question 6

Which equation correctly represents the activation of phospholipase C-γ in T-cell signal transduction?

Accepted Answer

$\mathrm{PIP_2} \xrightarrow{PLC-\gamma} \mathrm{IP_3} + \mathrm{DAG}$

Question 7

Which of the following is a key function of regulatory T cells (Treg) in the immune response?

Accepted Answer

Suppressing immune responses to maintain tolerance and prevent autoimmunity

Question 8

A cytotoxic T cell destroys a virus-infected cell primarily by:

Accepted Answer

Inducing apoptosis through perforin, granzymes, and Fas ligand interactions

Question 9

Which of the following best explains why costimulation is necessary for naïve T-cell activation?

Accepted Answer

It ensures T cells only respond to antigens presented by professional APCs, reducing the risk of autoimmunity.

Question 10

Helper T cells (Th1) activate macrophages at sites of infection by providing which two signals?

Accepted Answer

Interferon-gamma (IFN-γ) and CD40 ligand (CD40L)

Question 11

Which subset of helper T cells is primarily responsible for activating neutrophils to clear extracellular bacteria and fungi?

Accepted Answer

Th17 cells

Question 12

Natural killer T (NKT) cells are unique because they:

Accepted Answer

Recognize glycolipid antigens presented by CD1d molecules

Question 13

Which of the following is TRUE regarding B cells as antigen-presenting cells?

Accepted Answer

B cells present antigens specifically recognized by their immunoglobulin receptor via MHC class II pathway.

Question 14

Which signaling molecule is upregulated on dendritic cells after recognition of pathogen-associated molecular patterns (PAMPs) via toll-like receptors (TLRs)?

Accepted Answer

B7

Question 15

Which equation best represents the JAK-STAT pathway activation by cytokines in effector T cells?

Accepted Answer

$	ext{Cytokine} + 	ext{Receptor} \xrightarrow{JAK} 	ext{Phosphorylated STAT} ightarrow 	ext{Nucleus} ightarrow 	ext{Gene Expression}$

Question 16

A patient is unable to mount an effective immune response against extracellular parasites. Which helper T cell subset is most likely deficient?

Accepted Answer

Th2 cells

Question 17

Which of the following is a direct result of CTLA-4 expression on activated T cells?

Accepted Answer

Inhibition of T-cell proliferation by stronger binding to B7 molecules

Question 18

Which of the following steps occurs FIRST during the activation of a naïve T cell?

Accepted Answer

Formation of an immunological synapse between T-cell receptor and MHC-peptide complex

Question 19

Which equation best represents the formation of a high-affinity IL-2 receptor on activated T cells?

Accepted Answer

$	ext{IL-2R} = \alpha + \beta + \gamma$ (high-affinity complex)

Cell-Mediated Adaptive Immunity: T Cell Activation, Differentiation, and Effector Functions

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