Session 6 -Part II

Question 1

What are some examples of Antigen presenting cells?

Answer 1

Macrophages
Dendritic cells
Langerhans
B lymphocytes

Question 2

Briefly, state what Antigen presenting cells do

Answer 2

Capture
Process (breaks into peptides to present)
Present

Question 3

Where are antigen presenting cells usually found?

Answer 3

Mucus membranes
Layers of skin (skin associated lymphoid tissue) Nasal
Bronchial
Lymph system (Made of Spleen, lymph nodes and blood)

Question 4

What can an Antigen presenting cell do to a pathogen it has captured?

Answer 4

Phagocytosis

Micropinocytosis (engulfs ecf and extras eg toxins as well as microbe)

Question 5

Give an example of an intracellular pathogen

Answer 5

A virus

Question 6

Give an example of an extracellular pathogen

Answer 6

A bacteria

Question 7

What is MHC?

Answer 7

Major Histocompatability complex. Have class 1 & 2

Question 8

Where is MHC type 1?

Answer 8

On all nucleated cells

Question 9

What type of MHC presents viruses?

Answer 9

Type 1. Type 2 presents bacteria

Question 10

What type of T cell does MHC present to?

Answer 10

CD4+ for bacteria

CD8+ for viruses

Question 11

How do MHCs achieve their wide diversity of presenting?

Answer 11

They are co-dominant (both parental genes are expressed) and Polymorphic (Different alleles so more than one phenotype)

Question 12

What type of cell is CD4+ & CD8+?

Answer 12

T cells.

Question 13

Why are Antigen presenting cells so key to the immune response?

Answer 13

Because T cells won’t mount a response until it is activated by an antigen presenting cell

Question 14

What is the Peptide binding cleft?

Answer 14

Part of Major Histocompatability Complex where the peptide is presented to the T cell. It has different reidues lining it so can present different peptides from different microbes

Question 15

Why are viruses generally harder to present compared to bacteria?

Answer 15

Because they have a higher rate of mutation as soon as the Major Histocompatability Complex attempts to present it, the virus has changed

Question 16

What pathway do extracellular PAMP materials go through?

Answer 16

The endogenous pathway

Question 17

What pathway do intracellular PAMP materials go though?

Answer 17

The exogenous pathway

Question 18

What are PAMPs?

Answer 18

Pathogen-Associated Molecular Patterns - Molecules that act as markers for certain pathogens. Act on PRRs (Pathogen Recognition Receptor)

Question 19

Why do some people have fast progressing HIV?

Answer 19

The virus is mutating too fast for the MHCs to present it to the T cells

Question 20

Why do some people have slow progressing HIV?

Answer 20

The body manages to slow the virus mutating enough for the MHCs to present it to the T cells

Question 21

What is cross reactivity between antigens ?

Answer 21

Body doesn’t see difference between self and pathogen due to similar parts
Seen in autoimmune destruction (Type I Daibetes and Islets of Langerhans) and Graft Vs Host disease

Question 22

Where are T cells made and where do they mature?

Answer 22

Produced bone marrow, mature in thymus.

T cell receptor binds antigen

Question 23

Where are B cells made and where do they mature?

Answer 23

In the bone marrow and mature in the bone marrow as well

Question 24

What can CD4 become?

Answer 24

TH1 & TH2 (T helper cells)

Question 25

What can CD8 become?

Answer 25

Cytotoxic T cells (Release H202) | Memory cells

Question 26

Why is CD4 reduced involved in HIV? (Even though they usually fight bacteria)

Answer 26

Because they aid CD8 in clearing bacterial infections as well (Possibly due to differentiating into T helper cells)

Question 27

What are the different regions of a T cell receptor?

Answer 27

Variable region Constant region. (Variable has lots of diversity so bind peptides from MHC)

Question 28

What is a CD3 molecule?

Answer 28

A co receptor that aids the other T cells

Question 29

How does the Antigen presenting cell cause the CD4 cell to mature?

Answer 29

Gives 2 signals – B7 and MHC (Class 2 for bacterial, class 1 for viral)

Question 30

Once a T cell is mature, what prevents it from changing to another type of T cell?

Answer 30

Molecules prevent it from changing from one helper to other (cytokines) IL4/IL10 2->1 Suppresses 1 IFN gamma 1->2 Supresses 2. (Also enhancea macrophages phagocytosis.)

Question 31

What is the function of T helper 1 cells?

Answer 31

Suppress T helper 2. Enhances/activates Cytotoxic T cells Cell mediated immunity (Generally viruses)

Question 32

What is the function of T helper 2 cells?

Answer 32

Humeral response (Antibodies) Act on B cells --> plasma cells (produce antibodies) Suppress TH1. Activate Mast cells. (Involved in killing parasites) Attract and activate eosinophils Allergies Mucosal protection. BEST RESPONSE to extracellular microbes (Bacteria)

Question 33

How do B cells present antigens?

Answer 33

Have B cell receptors – Binds microbes, takes it in and processes it then presents it on MHC which shows it to T cell receptor (Have Antigen presenter diversity.)

Question 34

What happens once a B cell has presented the antigen?

Answer 34

Once presented it goes through clonal expansion & differentiation into plasma cells which produce antibodies. It can be activated by lipids or proteins (T cells only activated by peptides?)

Question 35

What are the different antibodies?

Answer 35

IgG (Opsonin. Enhances compliment pathway. Aids neonate immunity. Toxin and virus neutralisation) IgE (Parasite and mast cells) IgA (Mucosal immunity) IgM (Acitvates compliment pathway)

Question 36

What are some antibody based diagnostic tests?

Answer 36

Blood type HLA types Some disease diagnostic tests