Tophat questions Flashcards
Immature B and T lymphocytes share all of the following development processes before becoming mature EXCEPT:
selection for MHC restriction
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)?
it undergoes apoptosis
What type of selection is this? thymocyte does not bind to cTEC
positive selection of self-tolerant thymocyte
What type of selection is this?
thymocyte binds with low affinity to cTEC
positive selection of MHC-restricted thymocyte
What type of selection is this? thymocyte binds with high affinity to cTEC
negative selection of non-specific thymocyte = apoptosis
What type of selection is this? thymocyte does not bind to mTEC or DC
Death by neglect = apoptosis
What type of selection is this?
thymocyte binds to mTEC or DC
negative selection of autoreactive thymocyte = apoptosis
How does a double-positive thymocyte know which co-receptor (CD4 or CD8) to express when it becomes a single-positive thymocyte?
whether it binds to MHC I or MHC II on cTEC
What is the difference between central and peripheral tolerance in T cells?
Central tolerance uses mTEC to present thymic antigens. Peripheral tolerance uses mTECs to express self-antigens not native to the thymus
AIRE is a transcription factor expressed in mTECs. Why is this factor called the “autoimmune regulator?”
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.
What are the steps of T Cell development
- mature naive CD4/CD8 T lymphocytes leave thymic
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:
apoptosis
What is the co-receptor expressed by T cells that recognizes MHC I?
CD8
Which cell type expresses neither MHC I nor MHC II?
erythrocyte
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?
dendritic cells and macrophages
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.
B2-microglobulin is invariant because it doesnt affect antigen binding sites of MCH1 so it doesnt need gene recombination to make different variations.
Why is it easier to find a compatible blood transfusion than a compatible bone marrow transplant?
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.
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) .
endogenous / MHC I
Where in the APC are MHC molecules synthesized?
rough endoplasmic reticulum
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?
Helper T cells send interleukin 2 signals to Dendritic cells, initiating cross presentation
