Primer 30 - T Cells

Question 1

What does Interferon gamma (IFN-gamma) do?

Answer 1

Stimulates macrophages.

Question 2

What does IL-10 do?

Answer 2

Inhibits T cells and macrophages.

Question 3

What do IL-4 and IL-5 do?

Answer 3

They stimulate B cells.

Question 4

Where are T cells made and where do they differentiate?

Answer 4

They are manufactured in the bone marrow and they migrate to the thymus to differentiate.

Question 5

Describe the maturation process of the T cells.

Answer 5

When they arrive in the Cortex of the thymus, they are immature (they are both CD4+ and CD8+). As they mature, they lose the one positivity to become CD8 cytotoxic T cells or CD4 helper T cells.

Question 6

Where does Positive selection of T cells takes place?

Answer 6

Thymic cortex.

Question 7

Where does Negative selection of T cells takes place?

Answer 7

Thymic corticomedullary junction.

Question 8

What happens to the T cells that are selected in the negative selection?

Answer 8

They are removed by apoptosis.

Question 9

What are the two kinds of T helper cells?

Answer 9

Th1 and Th2 cells.

Question 10

What cytokine makes the T helper cell differentiate to Th1 cell and what factor for Th2?

Answer 10

Th1: IL-12.
Th2: IL-4.

Question 11

How do we stimulate the production of IL-12 cells and what does it do?

Answer 11

Viral infections stimulate the production of IL-12 that stimulates the production of Th1, which in turn stimulates the production of IL-2 and INF-gamma.

Question 12

What inhibits the production of Th1 and who is responsible for it?

Answer 12

Th1 is inhibited by IL-10, which is released by Th2 cells.

Question 13

What does Th1 stimulate?

Answer 13

The production of IL-2(which stimulates the production of T cells and cytotoxic T cells.) and INF-gamma (Which stimulates macrophages).

Question 14

What does Th2 stimulate?

Answer 14

Production of IL-10 which inhibits the development of Th1 cells and IL-4 and IL-5 which stimulates the production of B cells.

Question 15

What is MALT tissue?

Answer 15

The mucosa-associated lymphoid tissue (MALT) is a diffuse system of small concentrations of lymphoid tissue found in various mucosa sites of the body, such as the gastrointestinal tract, thyroid, breast, lung, salivary glands, eyes and skin.

Question 16

In what sites of the bodies do we find more Th1 cells?

Answer 16

In the dendritic cells, skin and lymph node areas.

Question 17

In what sites of the body do we find more Th2 cells?

Answer 17

Around the MALT (mucosa-associated lymphoid tissue) in order to stimulate IgA antibody production.

Question 18

Where does the thymus come from?

Answer 18

From the epithelium of the third brachial pouch.

Question 19

Where do mature T cells reside in the thymus?

Answer 19

In the medullar of thymus.

Question 20

What are the two signals to activate T cells?

Answer 20

On the surface of the Th is the TCR + CD4 complex and CD28 receptor. Said receptors need to unite to a molecule presented by a MHCII and B7 (AKA CD 80 or CD86), respectively on the cell that is presenting the molecule. This is called co-stimulation, stimulating the Th cell to produce cytokines.

Question 21

What do cytotoxic T cells do?

Answer 21

They look for virally infected cells to kill, neoplastic cells and non-self selfs (like donor grafts).

Question 22

What relevant receptors are on the surface of cytotoxic T cells in order to activate them?

Answer 22

Cytotoxic T cells have TCR+CD8 complex that recognizes an antigen presented in MHC I and CD28 that combines with B7 molecule on the cell that is presenting the antigen.

Question 23

How do we activate B cells to make immunoglobulins?

Answer 23

There are 4 main steps; 1.Endocytosis of antigen by B cells 2.Antigen is presented to a Th cell by using the MHC II found on APCs. 3. Use of costimulatory signal of CD40 receptor on B cells and CD40 ligand on Th cells. 4. The first 3 steps have induced the Th2 cells to generate IL-4,5,and 6 cells (These IL now promote activation and immunoglobulin class switching of the B cells).

Question 24

What does IL-2 do?

Answer 24

It is an important cytokine that is a T cell stimulator.

Question 25

Where do CD8 cells go after maturing in the thymus?

Answer 25

In the lymph nodes where they spend most of their time.

Question 26

How do cytotoxic T cells attack their targets and how?

Answer 26

By inducing apoptosis by the release cytotoxic granules that have preformed proteins like perforin and granzyme by the CD8 cells. They also express a molecule called FAS ligand, interacting with the fas receptor in the host cell, resulting in apoptosis.

Question 27

What are the two types of Regulatory T cells?

Answer 27

T regulatory CD4 cells and T suppressor CD8 cells.

Question 28

What does T regulatory CD4 cells do?

Answer 28

They express CD4 and CD25. They inhibit B cell antibody production and inhibit the generation of autoimmune disease.

Question 29

What do T suppressor CD8 cells do?

Answer 29

Suppress graft rejection and inhibit some autoimmune diseases.

Question 30

What do NK cells do?

Answer 30

They can kill other cells by using perforin and granzyme to induce apoptosis. They secrete IFN-gamma (which stimulates macrophages).

Question 31

How are NK cells induced to kill?

Answer 31

When appropriate ratio of activation signals are present on the target cell and the absence of specific inhibitory signals on the target cell (MHC I). Because NK cells do not need require helper T signals (like cytotoxic T cells) to attack, they are part of the early innate immune response to kill tumor and virally infected cells.

Question 32

What enhances the activity of NK cells?

Answer 32

Their activity is enhanced by IL-2, IL-12, interferon beta and interferon alpha.

Question 33

Which surface markers are on the surface of NK cells?

Answer 33

CD 16 and CD 56.

Question 34

What does CD16 do and where is it found?

Answer 34

It binds to the constant region of antibodies. Those with this CD can recognize and kill immunoglobulins coated cells by ADCC. They are found on NK cells, macrophages, monocytes, and neutrophils.

Question 35

Which cytokines are produced by Th1 cells? Which cytokines are produced by Th2 cells?

Answer 35

Th1: IL-2 and IFN-gamma which leads activation of CD8 cells and macrophages. Th2: IL-4, IL-5, IL-10, which lead to activation of B cells and Ab production.

Question 36

Which cytokines inhibit Th1 cells? Which cytokines inhibit Th2 cells?

Answer 36

Th1 is inhibited by IL-10 while Th2 is inhibited by Th2.