#3 Cytotoxic Cell-Mediated Immune Response

Question 1

Where does Ag independent maturation of T-cells occur?

Answer 1

In thymus

Only stem cells are from the bone marrow

Question 2

How are naive T cells activated?

Answer 2

By dendritic cells

Langerhans’ cells enter lymph node to become dendritic cells expressing B7

Question 3

Where is the T cell zone in the lymph node?

Answer 3

parafollicular cortex

DC loaded with Ag and moved to T cell zone located in the parafollicular cortex

Naive T cells enter LN via blood stream

Question 4

What do the co-receptors on CD4 and CD8 cells do?

Answer 4

Help to concentrate the attention of the T cell to the proper MHC

CD4 and CD8 are signaling co-receptors

Question 5

What leads to clustering of TCRs?

Answer 5

Ag recognition by several TCRs

Question 6

How is activation of T cells initiated?

Answer 6

To activate a T cell, we need ALL: TCR, CD3, CD4 or CD8

Question 7

Co stimulation for T cell

Answer 7

CD80-CD28

B7 proteins (CD80/CD86) on the APC bind to CD28 (on T-cell)

Question 8

Autocrine signaling and T cells

Answer 8

Newly activated T cells make IL-2 and use it to stimulate themselves to proliferate (# of activated T cells is doubled every 6 hours)

Question 9

What is the T-cell growth factor?

Answer 9

IL-2…they then express IL-2R (receptor)

Naive T cells don’t have IL-2 receptor

Question 10

Re-Stimulation of Activated T cell

Answer 10

Called “T cell homing” → going to tissue from where dendritic cell came from

2nd signal comes from MΦ

Question 11

Co-stimulation options:

Answer 11

B7-CD28

CD40 (on APC)-CD40L (on B cells)

INC B7/MHC expression

Question 12

Upregulation of CD40L protein does what?

Answer 12

Required for helping activated B cells

Question 13

How are CD8+ T cells activated?

Answer 13

Cross-presentation of antigens

Question 14

Cross-presentation of Ags

Answer 14

Some viral Ags are released from phagosome in cytoplasm of DC and then presented within class 1 MHC

They also display them within MHC class 2 for CD4+ helper T cells

Question 15

CD8+ cells kill in 2 ways

Answer 15

1. Granzyme and perforin

2. Fas-L-Fas (CD95): induces apoptosis via caspase activation

Question 16

Nontraditional T cells

Answer 16

• Most don’t express CD4 or CD8 co-receptors
• Abundant in intestine, uterus, tongue. We don’t know if educated in thymus
• T reg, 1st line of defense, bridging between innate and adaptive

Question 17

Nontraditional T cells can have a rearrangement of their TCR genes to produce junctional diversity

Answer 17

True

Don’t need APC (not MHC restricted)

Question 18

NKT cells vs NK cells

Answer 18

NKT cells:

• Share CD markers of both T and NK cells
• Recognize lipids and glycolipids (via CD1d (like MHC))

Question 19

When NKT cells are activated, what do they produce in large quantities?

Answer 19

IFN-γ and IL-4

Rapidly release cytokines. They can promote or suppress different immune responses

Question 20

What does dysfunction or deficiency of NKT lead to? (3)

Answer 20

Autoimmunity (diabetes or atherosclerosis)

Cancers

Progression of asthma