Exam (elaborations)
Immunology Exam 4 Review Ch 7 & 8 with 100% correct answers
- Course
- PCB 3233
- Institution
- University Of Central Florida
Immunology Exam 4 Review Ch 7 & 8 with 100% correct answers
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Immunology Exam 4 Review Ch 7 & 8Development (maturation) of T cells, where does it take place? - correct answer ✔✔Thymus
What gene segments are rearranged for the alpha and beta chains? - correct answer ✔✔Alpha: VJ
Beta: VDJ
Are the RAG genes used in the rearrangement? - correct answer ✔✔Yes
What makes up pre-TCR? - correct answer ✔✔Beta chain and pt-alpha (surrogate alpha chain) + CD3 +
zeta chain
Know what IL-7 and Notch-1 do and when they exert their influence on developing T-cells - correct
answer ✔✔Notch-1 is a simple signaling mechanism in the thymus during the maturation process, signal
sent on all stages of maturation to drive T cells in their differentiation
IL-7 help T cell on what to do on the next step of its maturation
DiGeorge's syndrome. What is the cause? What chromosome is involved? What organ is involved? -
correct answer ✔✔A deletion of chromosome 22 in which the thymus fails to develop and T cells are
absent. This will make a person susceptible to a wide range of opportunistic infections. Resembles SCID;
genetic disease.
"Double negative" thymocytes; Why are they called this and where would you find them in the body? -
correct answer ✔✔Immature T cells in the thymus that do not express CD4 or CD8. Gene rearrangement
has begun. Posses CD2, CD5, CDiA and IL-7 receptor.
Are RAG-1 and 2 working in somatic recombination of T-cells genes also? What about the 12/23 rule (1/2
turn rule)? - correct answer ✔✔yes and yes
The 12/23 rule applies.
, Which takes place first positive or negative selection? Where does positive selection take place and
where does negative selection take place? - correct answer ✔✔Positive selection takes place first and
occurs in the cortex of the thymus. This process ensures that T cells 1st recognize YOUR MHC molecules.
Negative selection occurs next in the medulla of the thymus. This process will initiate apoptosis upon T
cells whose antigen receptors BIND TOO STRONGLY to the complexes of self peptides and self MHC
molecules presented by thymic cells.
Lifespan of a T cell, short or long compared to a B-cell. - correct answer ✔✔Long
If you are heterozygous for the MHC (HLA) genes how many presenting MHC (HLA) molecules do you
have? - correct answer ✔✔12 MHC molecules, which you can bind 120,000 different peptides
Thymocytes gene rearrangement; b, g and d chain genes (when) - correct answer ✔✔About the same
time. Gamma and Delta "race" with Beta, if GD wins it becomes a committed GD cell. If B wins a second
"race" starts with GD and alpha. IF GD wins it becomes a committed GD cell. If A wins it becomes a
committed AB cell. AB wins the vast majority of the time.
Deletion of the d chain genes how does this happen and when does this happen? - correct answer
✔✔When the alpha chain gene is rearranged the delta chain will be automatically deleted.
Which type of T cell receptor predominates αβ or γδ? - correct answer ✔✔Alpha-Beta
Rearrangement of a b-chain, how many possible attempts do they have to make a functional
rearrangement. - correct answer ✔✔4
When are CD 4 and 8 co-expressed, before or after beta chain rearrangement? When is a thymocyte
considered a single positive cell (before or after positive selection)? - correct answer ✔✔After Beta chain
rearrangement.
after positive selection
What is positive selection? Where is it done, what cells mediate it, what is being checked and what
happens to the T-cell? - correct answer ✔✔Positive selection takes place in the cortex of the thymus and
is mediated by cortical epithelial cells bearing complexes of class 1 and class II self-MHC and self
peptides. Testing for recognition of self-MHC and self-peptide on abTCR of thymocytes.
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