Question 1

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

Accepted Answer

They phagocytose pathogens, migrate to lymph nodes, and present antigens on MHC II (or MHC I if the pathogen is cytosolic) to activate matching naïve T cells.

Question 2

Which signal is required for full activation of a naïve T cell by an antigen-presenting cell (APC), and what is the consequence if this signal is absent?

Accepted Answer

Signal 2: CD28 on T cell binding B7 on APC; absence leads to T cell anergy.

Question 3

Which effector T cell subtype is primarily responsible for activating macrophages to enhance their ability to kill intracellular bacteria?

Accepted Answer

CD4 T\_{H}1 cells

Question 4

A patient with lepromatous leprosy shows high antibody production but poor containment of Mycobacterium leprae. Which T cell response is dominant in this patient?

Accepted Answer

T\_{H}2 response, promoting antibody production and suppressing inflammation.

Question 5

Which molecule on the T cell acts as a competitive inhibitor of CD28, downregulating IL-2 production and preventing dangerous overactivation?

Accepted Answer

CTLA-4

Question 6

What is the primary function of CD8 cytotoxic T cells in cell-mediated immunity?

Accepted Answer

Kill virus-infected cells by inducing apoptosis.

Question 7

Which cytokine is most associated with the promotion of T\_{H}1 differentiation and activation of macrophages?

Accepted Answer

IL-12

Question 8

During the activation of a naïve CD8 T cell, which helper cell and cytokine are typically required to enhance the process?

Accepted Answer

CD4 T cell and IL-2

Question 9

Which process describes the removal of potentially self-reactive immature lymphocytes during T cell development?

Accepted Answer

Negative selection

Question 10

A mutation prevents the expression of B7 on dendritic cells. What is the most likely outcome for T cells encountering antigen presented by these dendritic cells?

Accepted Answer

T cells become anergic due to lack of co-stimulation.

Question 11

Which effector molecule produced by cytotoxic T cells directly induces apoptosis in target cells by binding to Fas?

Accepted Answer

FasL (Fas ligand)

Question 12

Which type of T cell is most important for supporting B cell isotype switching and antibody production, especially IgE?

Accepted Answer

CD4 T\_{H}2 cells

Question 13

Which cytokines are produced by regulatory T cells to suppress immune responses and prevent autoimmune disease?

Accepted Answer

IL-10 and TGF-\beta

Question 14

Which of the following best explains why granulomas form in response to certain intracellular bacteria such as Mycobacterium tuberculosis?

Accepted Answer

Activated macrophages fail to kill bacteria in lysosomes, leading to containment by surrounding T cells and macrophages.

Question 15

Which step in T cell development ensures that mature T cells do not react strongly with self antigens?

Accepted Answer

Negative selection in the thymus

Question 16

Which of the following is a key difference between B cells and dendritic cells as antigen-presenting cells (APCs)?

Accepted Answer

Dendritic cells are strong phagocytes and present diverse antigens, while B cells present antigens specifically bound to their surface immunoglobulin.

Question 17

Which effector T cell subtype is most associated with enhancing neutrophil recruitment and promoting barrier integrity in tissues such as the skin and intestine?

Accepted Answer

CD4 T\_{H}17 cells

Question 18

Which molecule must be expressed on B cells and bound by CD40L on helper T cells for B cell activation and isotype switching?

Accepted Answer

CD40

Question 19

A patient is unable to produce IL-2 after T cell activation. Which process will be most directly impaired?

Accepted Answer

Clonal expansion and differentiation of activated T cells

Question 20

Which of the following best describes the role of CTLA-4 in peripheral tolerance?

Accepted Answer

CTLA-4 competes with CD28 for B7 binding, downregulating T cell activation and preventing autoimmunity.

Cell-Mediated Immunity: T Cell Activation and Effector Functions

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