Question 1

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

Accepted Answer

They present antigens on MHC II molecules after phagocytosis and migrate to lymph nodes to activate matching T cells.

Question 2

Which signal is required for full activation of a naive 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 to 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\_{H1} cells

Question 4

A patient with lepromatous leprosy shows high antibody production but poor control of intracellular bacteria. Which T cell response is dominant in this patient?

Accepted Answer

T\_{H2} response, characterized by IL-4 and antibody production

Question 5

Which molecule acts as a competitive inhibitor of CD28 signaling in T cells, thereby downregulating IL-2 production and preventing overactivation?

Accepted Answer

CTLA-4

Question 6

What is the primary function of regulatory T cells (T\_{reg}) in the immune system?

Accepted Answer

Suppress Th1 and Th2 responses and prevent autoimmune disease by producing IL-10 and TGF-\beta

Question 7

Which cytokine is most associated with the proliferation and differentiation of activated T cells after initial priming?

Accepted Answer

IL-2

Question 8

During the activation of CD8 T cells, which helper cell and cytokine are crucial for upregulating B7 on APCs and increasing the likelihood of CD8 activation?

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 dendritic cell presents a cytosolic viral antigen. Which MHC molecule is used for presentation, and which T cell subtype is activated?

Accepted Answer

MHC I; CD8 cytotoxic T cell

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 of the following best explains why antibodies are not effective against bacteria residing inside macrophages in lepromatous leprosy?

Accepted Answer

Antibodies cannot penetrate the intracellular environment; cell-mediated immunity is required.

Question 13

Which combination of signals is required for the activation of a naive B cell by a helper T cell?

Accepted Answer

CD40 on B cell binding to CD40L on T cell, plus antigen recognition

Question 14

Which effector T cell subtype is most important for fighting helminth (parasitic worm) infections?

Accepted Answer

CD4 T\_{H2} cells

Question 15

Which cytokine is produced by T\_{reg} cells to suppress macrophage activity and promote immune tolerance?

Accepted Answer

IL-10

Question 16

A patient is unable to form granulomas in response to Mycobacterium tuberculosis infection. Which T cell response is likely deficient?

Accepted Answer

T\_{H1} response

Question 17

Which process allows effector T cells to migrate to sites of infection after activation in the lymph node?

Accepted Answer

Expression of chemokine receptors and integrins that facilitate rolling and migration through high endothelial venules (HEVs)

Question 18

Which transcription factor is most associated with the differentiation of T\_{H1} cells?

Accepted Answer

T-bet

Question 19

Which cytokine promotes switching of B cells to produce IgA and inhibits clonal expansion of T and B cells?

Accepted Answer

TGF-\beta

Question 20

Which effector T cell subtype is most important for enhancing neutrophil response and promoting barrier integrity in the intestine?

Accepted Answer

CD4 T\_{H17} cells

Cell Mediated Immunity: T Cell Activation and Effector Functions

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