Tophat questions

Question 1

Immature B and T lymphocytes share all of the following development processes before becoming mature EXCEPT:

Answer 1

selection for MHC restriction

Question 2

What happens to a double-positive thymocyte whose TCR binds with high affinity to a peptide presented with MHC I by a cortical thymic epithelial cell (cTEC)?

Answer 2

it undergoes apoptosis

Question 3

What type of selection is this? thymocyte does not bind to cTEC

Answer 3

positive selection of self-tolerant thymocyte

Question 4

What type of selection is this?

thymocyte binds with low affinity to cTEC

Answer 4

positive selection of MHC-restricted thymocyte

Question 5

What type of selection is this? thymocyte binds with high affinity to cTEC

Answer 5

negative selection of non-specific thymocyte = apoptosis

Question 6

What type of selection is this? thymocyte does not bind to mTEC or DC

Answer 6

Death by neglect = apoptosis

Question 7

What type of selection is this?

thymocyte binds to mTEC or DC

Answer 7

negative selection of autoreactive thymocyte = apoptosis

Question 8

How does a double-positive thymocyte know which co-receptor (CD4 or CD8) to express when it becomes a single-positive thymocyte?

Answer 8

whether it binds to MHC I or MHC II on cTEC

Question 9

What is the difference between central and peripheral tolerance in T cells?

Answer 9

Central tolerance uses mTEC to present thymic antigens. Peripheral tolerance uses mTECs to express self-antigens not native to the thymus

Question 10

AIRE is a transcription factor expressed in mTECs. Why is this factor called the “autoimmune regulator?”

Answer 10

AIRE causes mTECs to express major proteins from parts of the body besides the thymus to fully test if the T cells are self-reactive. If T cells bind to these proteins they will undergo apoptosis.

Question 11

What are the steps of T Cell development

Answer 11

1. mature naive CD4/CD8 T lymphocytes leave thymic

Question 12

When the TCR of a mature naive T lymphocyte binds to the correct peptide-MHC complex, intracellular signalling in the T cell will result in all the following EXCEPT:

Answer 12

apoptosis

Question 13

What is the co-receptor expressed by T cells that recognizes MHC I?

Answer 13

CD8

Question 14

Which cell type expresses neither MHC I nor MHC II?

Answer 14

erythrocyte

Question 15

Professional antigen-presenting cells use MHC I and MHC II to present antigens to and activate mature naive T lymphocytes. Which pair of leukocytes are professional APCs?

Answer 15

dendritic cells and macrophages

Question 16

Both MHC I and II are comprised of two polypeptide chains each. While both chains of MHC II are created by genetic recombination, only one chain of MHC I is recombined. Why is the second chain of MHC I, called B2-microglobulin, invariant? Hint: Compare the structures of MHC I and II.

Answer 16

B2-microglobulin is invariant because it doesnt affect antigen binding sites of MCH1 so it doesnt need gene recombination to make different variations.

Question 17

Why is it easier to find a compatible blood transfusion than a compatible bone marrow transplant?

Answer 17

Most nucleted cells of the body contain MHC 1, including the cells of the bone marrow. However, non-nucleated cells, like erythrocytes, do not contain MHC 1. So, when giving a blood transfusion only the type has to be matched, whereas when giving a bone marrow transplant there needs to be assurance that the T lymphocytes won’t become activated and attack the new bone marrow.

Question 18

If a virus infects a host cell, its antigens be processed via the (FILL-IN-THE-BLANK) pathway and presented with (FILL-IN-THE-BLANK) .

Answer 18

endogenous / MHC I

Question 19

Where in the APC are MHC molecules synthesized?

Answer 19

rough endoplasmic reticulum

Question 20

If a virus cannot infect a dendritic cell (DC), the virus will be phagocytosed and its antigens will be cross presented with MHC I, so that CD8 T cells can be activated for a cytotoxic response. How does the DC know that these phagocytosed antigens should be cross presented?

Answer 20

Helper T cells send interleukin 2 signals to Dendritic cells, initiating cross presentation