Antigen Receptor and Lymphocyte Development

Question 1

What is an antigen?

Answer 1

Antigen (Ag) is a molecule which specifically binds a T-cell receptor or an antibody (Ab) site

Question 2

What is an immunogen?

Answer 2

Any molecule that elicits an immune response by binding to a T-cell receptor or an antibody

Question 3

What are the specific immune receptors of the adaptive immune response?

Answer 3

T-cell receptors (TCR)
B-cell receptors (BCR)

These receptors are formed/generated to aid in immune response.

Question 4

What are the preformed antigen receptors?

Answer 4

PRR
TLR
CR
Fc

These act in the innate system. They are general, preformed antigens. NOT SPECIFIC.

Question 5

What antibodies are displayed on mature B-cells?

Answer 5

IgM

IgD

Question 6

When is the constant region spliced during Ig development?

Answer 6

During RNA processing

Question 7

What creates diversity in the development of Igs?

Answer 7

TdT–transferase protein, adds nucleotides to the end before ligase proteins seal segments together.

Question 8

TdT is present in which cells only?

Answer 8

B-cells

Question 9

Where do B cells mature?

Answer 9

Follicular region of lymph node

Question 10

Where does a B cell become activated?

Answer 10

In the paracortex of a lymph node

Question 11

Which region is combined first in Ig recombination?

Answer 11

D-J

Question 12

RSSs contain how many base pairs?

Answer 12

12 or 23

Question 13

What is an RSS?

Answer 13

Recombination Segment Sequence

Part of the V, D, J regions on genes for Igs

Question 14

How many RSSs do V, D, and J have?

Answer 14

V: 1
D: 2 (joins with both V and J)
J: 1

Question 15

What opens the hairpin loop to allow nucleotide addition to the immunoglobulin?

Answer 15

Artemis (protein enzyme)

Question 16

Where do naive T-cells enter the thymus?

Answer 16

Corticomedullary area

Question 17

What guides T cells to the thymus?

Answer 17

CCR9 (receptor on thymocyte) + CCL25

Question 18

Which chemokine is essential in bringing T cell precursors into the corticomedullary thymus?

Answer 18

CCR9

Question 19

What does CCR9 bind to?

Answer 19

CCL25

Question 20

Where is CCL25 produced?

Answer 20

The cortex of the thymus

Question 21

Which chemokines guide the T cell from the cortex to the medulla during maturation?

Answer 21

CCR7 receptor (on thymocyte) + CCL21 and CCL19

Question 22

Where do positive and negative selection of T cells occur?

Answer 22

Positive: Cortex
Negative: Medulla

Question 23

When do T cells begin displaying CD3?

Answer 23

When they become DN3

Question 24

When do T cells display CD25?

Answer 24

DN2

DN3

Question 25

What does CD25 bind to?

Answer 25

IL-2

Question 26

When is a thymocyte committed to becoming a T cell?

Answer 26

After DN3 –> it is now displaying a TCR

Question 27

What must happen for a T cell to finish positive selection and enter negative selection?

Answer 27

TCR must interact with self MHC. If it does not, apoptosis will occur.

Question 28

Where do T cells become single positive cells?

Answer 28

Medulla

Question 29

What promotes the elimination of auto-reactive T cells in the medulla?

Answer 29

AIRE (auto-immune regulator protein–>transcription factor)

Question 30

What drives negative selection of single positive T cells in the medulla?

Answer 30

AIRE

Question 31

What is CD44?

Answer 31

Adhesion molecule on thymocytes

Question 32

Which chain is developed first in T cell maturation?

Answer 32

Beta chain