Name _________________________________________ TA/Section ____________________
MCDB 133 W19 Midterm #2 (100 pts) – KEY
Grade Stats: 18 people scored 100 or above. Grades are as follows: >/= 90 = A; >/=80 = B; >/=67 =
C. >52 = D. Re-grade Policy is same as before, all re-grades need to be to me after lecture by
Monday, 4/11.
1. CD4 and CD8 binding are required for TCR signaling. Cells would be initially DP because the
cell does not yet know if the newly recombined TCR binds to Class I or Class II MHC, so would
need both molecules on cell surface such that signaling could occur upon binding.
2. Naïve cells need BAFF stimulation or they will die, requiring they migrate into the lymph
node and come into contact with a FDC. This is a quality control mechanism (don’t need to say
that specifically). Activated B-cells can die if they lose during affinity maturation. This ensures
that only the highest affinity binders survive. Both processes are based on competition.
One answer I’ve seen a lot is that’s where negative selection occurs. That’s a partial credit, as
not required to be in lymph node for selection.
3. They need to be physically linked to a protein that will be presented in MHC Class II, in order
to stimulate TFH cells. They also need a co-stimulatory signal from the TFH cell.
4. Death or receptor editing during development. Death or anergy in the periphery.
For second: Central and peripheral tolerance, clonal deletion.
5. Affinity Maturation: improved affinity binding
CSR: adding right functionality to antibody to get correct response.
6. Multiple answers: FDC vs pAPC; peptide vs whole antigen; requires MHC or not; requires
protein destruction vs not…..any differences accepable.
7a CD4 SP- no MHC II, no positive selection for CD4+
b. Nothing would change for development, BUT autoreactive cells would be released.
c. Both CD4 SP and CD8 SP…but since cells start to go DP with expression of pre-TCR, you
can accept just DP…
Extra Credit (6 pts):
A. Lineage Commitment or positive selection B. Negative Selection C. Positive
Selection
1
This study source was downloaded by 100000850872992 from CourseHero.com on 02-13-2023 02:19:10 GMT -06:00
https://www.coursehero.com/file/39085332/2019-Midterm-2-Keypdf/
MCDB 133 W19 Midterm #2 (100 pts) – KEY
Grade Stats: 18 people scored 100 or above. Grades are as follows: >/= 90 = A; >/=80 = B; >/=67 =
C. >52 = D. Re-grade Policy is same as before, all re-grades need to be to me after lecture by
Monday, 4/11.
1. CD4 and CD8 binding are required for TCR signaling. Cells would be initially DP because the
cell does not yet know if the newly recombined TCR binds to Class I or Class II MHC, so would
need both molecules on cell surface such that signaling could occur upon binding.
2. Naïve cells need BAFF stimulation or they will die, requiring they migrate into the lymph
node and come into contact with a FDC. This is a quality control mechanism (don’t need to say
that specifically). Activated B-cells can die if they lose during affinity maturation. This ensures
that only the highest affinity binders survive. Both processes are based on competition.
One answer I’ve seen a lot is that’s where negative selection occurs. That’s a partial credit, as
not required to be in lymph node for selection.
3. They need to be physically linked to a protein that will be presented in MHC Class II, in order
to stimulate TFH cells. They also need a co-stimulatory signal from the TFH cell.
4. Death or receptor editing during development. Death or anergy in the periphery.
For second: Central and peripheral tolerance, clonal deletion.
5. Affinity Maturation: improved affinity binding
CSR: adding right functionality to antibody to get correct response.
6. Multiple answers: FDC vs pAPC; peptide vs whole antigen; requires MHC or not; requires
protein destruction vs not…..any differences accepable.
7a CD4 SP- no MHC II, no positive selection for CD4+
b. Nothing would change for development, BUT autoreactive cells would be released.
c. Both CD4 SP and CD8 SP…but since cells start to go DP with expression of pre-TCR, you
can accept just DP…
Extra Credit (6 pts):
A. Lineage Commitment or positive selection B. Negative Selection C. Positive
Selection
1
This study source was downloaded by 100000850872992 from CourseHero.com on 02-13-2023 02:19:10 GMT -06:00
https://www.coursehero.com/file/39085332/2019-Midterm-2-Keypdf/
