Immunology lecture 4- eliminating pathogens that live outside of the cell

Question 1

Which intracellular bacteria cause the following diseases?

1. Respiratory infections
2. Legionnaire’s
3. Listeriosis
4. Meningitis
5. Typhoid fever
6. TB

Answer 1

1. Chlamydia pneumoniae
2. Legionella pneumophila
3. Listeria monocytogenes
4. Neisseria meningitidis
5. Salmonella typhi
6. Mycobacterium tuberculosis

Question 2

Modes of action to kill viraly or bacterially infected cells

Answer 2

Cytotoxic T cells
NK cells
Macrophages

Question 3

Describe now Cytotoxic T cells are activated

Answer 3

Binds to antigen presented on MHC class 1 molecule on dendritic cell in lymph nodes. Multiplies then leaves the lymph nodes and follows inflammatory signals to sight of infection

Question 4

What are the 2 receptors located cytotoxic T cells?

Answer 4

TCRaB (alpha beta)

CD8 co-receptor

Question 5

Which cell in the body does not present MHC class 1 receptor?

Answer 5

Red blood cells- has nu nucleus

Question 6

What mechanism does Cytotoxic T cells use to kill infected cells presenting a segment of the pathogen on its ,MHC class 1 receptor

Answer 6

Apoptosis

Question 7

Describe what apoptosis does to the cell

Answer 7

Cell digested from the inside
Cell Membrane kept intact
Nuclear blebbing occurs
Small mambrane fragments (vesicles) are shed
Nucleus is fragmented by nuclease enzymes
The fragments (apoptotic bodies) are removed by phagocytic cells

Question 8

How do cytotoxic T cells initiate apoptosis?

Answer 8

They use lytic granules (modified lysozymes) which have 2 powerful agents

Question 9

What are the two powerful agents of lytic granules?

Answer 9

Perforin- Forms pores in the target cells membrane

Granzymes- proteases which bind to proteins on cell membrane, enter the cell then cut up proteins in the target cell

Question 10

How do cytotoxic T cells differentiate between infected and not infected cells

Answer 10

They conducted non specific adhesion
Grabs onto any cell using receptors. Assess if the cell has a MHC class 1 receptor presenting the same antigen.
If no, it releases the cell and looks for another

If yes it uses TCR: MHC peptide interactions to pull the infected cell closer and exert its responce

Question 11

Type of cells cytotoxic T cells kill?

Answer 11

Infected cells and tumour cells

Question 12

Are natural kill cells part of the innate or adaptive immune system?

Answer 12

Innate immune system

Question 13

Are natural killer cells lymphocytes?

Answer 13

Yes

Question 14

Difference between NK cells and other lymphocytes?

Answer 14

Do not have antigen specific receptors

Question 15

Which method of cell death do Nk cells use?

Answer 15

Same at T lymphocytes

Perforin and granzymes

Question 16

What is activates NK cell?

Answer 16

Cytokines

Question 17

What does NK cells secrete?

Answer 17

Interferon gamma

Question 18

How do NK cells know a cell is infected and avoid killing normal cells

Answer 18

Missing self hypothesis
Recognition of “self” = No killing by NK cells

Recognition of “missing-self” = Killing by NK cells

Question 19

When a cell is not infected what sits in the MHC class 1 molecule?

Answer 19

Self antigen

Question 20

How does an NK cell recognise self antigens?

Answer 20

When NK cells develop in the bone marrow they are programmed to identify your MHC class 1 molceule. So it goes to different cells in the body and ensures this MHC class 1 molecule is being presented

Question 21

Function of inhibitory receptor and activating receptor in NK cells

Answer 21

Inhibitory- binds to side of MHC molecule to ensure it is present and self

Question 22

What do some viruses do to the MHC class 1 molecules present on human cells? How does theis activate NK cells

Answer 22

They down regulate MHC class 1 so it is no longer expressed on the surface of the cell.
When the NK cell assess if the cell has MHC class 1 the answer will be no.
So the NK cell kills the cell.
Tumours work the same way