Effector Responses: Cell-Mediated Immunity

Question 1

What is cell-mediated immunity?

Answer 1

• involves T lymphocytes
• clear infected self-cells
• eradicate intracellular pathogens

Question 2

TCR activation allows for ….

Answer 2

• CTLs recognition and kill infected/tumor cells

Question 3

List the 3 signals of cell-mediated effector functions.

Answer 3

Signal 1: TCR engagement binds peptide with MHC class I
Signal 2: costimulatory signal by CD80/86 on APC and CD28 on T cell
Signal 3: Cytokine production (IL-2) induces proliferation

Question 4

List the pathways of cell-mediated effector functions once they recognize infected MHC class I.

Answer 4

Intrinsic pathways: perforin punches holes in target cell membrane and granzymes induce apoptosis
Extrinsic pathways: FasL on cytotoxic T cell binds Fas and initiates death leading to apoptosis

Question 5

Do NK cells have PRRs?

Answer 5

No, they have inhibitory and activation receptors

Question 6

What type of selection do NK cells undergo so that it does not attack the healthy cell?

Answer 6

Negative Selection

Question 7

How do NK cells recognize and target virus-infected cells?

Answer 7

• lack of MHC class I expression due to virus defense mechanism
• NK cell’s inhibitory receptors are not used causing cell to be killed

Question 8

Explain.

Answer 8

1. There is a balance of inhibitory and activation receptors
2. NK cell is activated because there are more activation receptors that override inhibitory receptors