Antigens and Adaptive Immunity

Question 1

MO active Th cells. Th cells then can activate what?

Answer 1

Can either active Cytotoxic T cells/ CD8
OR
B cells.

Question 2

What do Cytotoxic T cells target?

Answer 2

Virally or cancerous infected cells. Also targets cells that are involved with autoimmune diseases and non-self cells involved with grafts.

Question 3

What do B cells target?

Answer 3

Bacteria and toxins in Solution

Question 4

4 Key Antigen characteristics?

Answer 4

Degree of foreignness to host.
Size (mannose vs hapten)
Chemical complexity
Amount (threshold)

Question 5

3 main APCs

Answer 5

Dendritic cells especially

MO and B cells

Question 6

What are dendritic cells?

Answer 6

The main APC. Resident of epithelial tissue. Binds AG in epithelial tissue and presents it on outside of cell. Travels to secondary lymphoid tissue and presents to naive T cell

Question 7

Primary lymphoid tissue

Answer 7

Bone marrow, Thymus

Question 8

Secondary lymphoid tissue

Answer 8

Spleen, lymph nodes, Tonsils, Adenoids, MALT (mucosal associated lymphoid tissues), Peyers patches

Question 9

MHC on which chromosome. Which genes?

Answer 9

On short arm of Chromosome 6. Involves genes VDJ

Question 10

What is MHC?

Answer 10

a glycoprotein. MHC1 on all nucleated cells. MHCII only on professional APCs

Question 11

MHCI
On which cells?
Presents to who?
Presents what?

Answer 11

On all nucleated cells.
Presents to Cytotoxic T cell (CD8)
Presents endogenous protein. Normal? No response by CD8. Abnormal? CD8 will initiate response based on if is viral or cancerous.

Question 12

MCHII
On which cells?
Presents to who?
Presents what?

Answer 12

On professional APCs only- dendritic, MO, B cell.
Presents to CD4- T helper cells. which can then activate CD8 or B cells.
Presents exogenous epitope. APC engulfs, processes, and presents epitope for APC.

Question 13

Epitope and paratope?

Answer 13

Epitope: Portion of antigen.
Paratope: Variable portion on T or B cell or AB binding site. Part that binds epitope.

Question 14

4 characteristics of Ag- receptor binding?

Answer 14

1. Weak bonds. Electrostatic, hydrogen. Non-covalent.
2. Affinity. Strength of bond.
3. Valence. How many arms/binding site does the receptor have? B cells- bivalent. T cells- monovalent.
4. Avidity. Total bond. Combo of affinity and valence.

Question 15

Clonal diversity 
what is it? 
Where does it occur?
What happens?
Result?

Answer 15

Somatic recombination creates unique Ab receptor.
Occurs in primary lymphoid organs.
VDJ gene segments cut and spliced on CHR 6 short arm.
Result: Naive but immunocompetent T and B cells.

Question 16

Clonal deletion
What happens?
What is the outcome?

Answer 16

Self reactive B and T cells are destroyed. Generates central/self tolerance.

Question 17

Clonal selection

Answer 17

APCs present Ags to the naive lymphocytes in secondary lymphoid tissue.
If a match is made, the activated lymphocyte will proliferate.

Question 18

How are T cells activated

Answer 18

T cell Receptor must bind to Ag presented by MHCII complex on APC

Question 19

How are B cells activated

Answer 19

B cell receptor bound to bacteria that enters secondary lymphoid tissue.

Question 20

Activation of CH4 helpers (3)

Answer 20

T cell receptor binds to MHCII with Ag on APC.
Co stimulatory signals
Cytokine stimulation by APC. APC releases IL-1.

Question 21

Activation of CD8 CTLs (3)

Answer 21

T cell receptor binds to MHCI with Ag on any nucleated cell.
Co stimulatory signal
Cytokine stimulation by Th1 cells releasing IL-2

Question 22

Subtypes of T helper

Answer 22

Th1: Cellular pathway. Activates CD8
Th2: Humoral pathway. Activates B cell.
T reg: peripheral tolerance (makes sure there aren’t any self reactive lymphocytes in secondary lymphoid tissue. Also can turn off immune response.)
T memory cells.

Question 23

4 main goals of T helper cells

Answer 23

1. Initiate maturation of B and T cells. Driven by antigens.
2. Recognize specific Ag by MHCII presentation.
3. Differentiate into effector/memory cells when activated.
   - Th1: Cellular pathway. Activates CD8
   - Th2: Humoral pathway. Activates B cells
   - Treg: Peripheral tolerance and turn off.
   - Memory
4. Facilitates. Assists effectors (Tc and B cells) with cytokines. Tells them what to do.