MIMG C185A Final Exam | Questions and
Answers | 2025 Revised Update | 100%
Correct - UCLA
SECTION 1: MHC STRUCTURE AND GENETICS
1. An inbred (syngeneic) strain of mice (UCLA mice) has the following MHC locus
organization: K, I-Aα, I-Aβ, I-Eα, I-Eβ, D, L, L. How many different types of MHC I
molecules will these mice express on the surface of their antigen-presenting cells
(APCs)?
A) 2
B) 4
C) 6
D) 8
E) 9
Correct Answer: D
Rationale: The MHC locus shows 9 genes total: K, I-Aα, I-Aβ, I-Eα, I-Eβ, D, L, L. The L gene
is duplicated. Since the mice are inbred, both maternal and paternal MHC I genes are
, identical. However, the duplicated L gene produces two identical proteins that are not
distinct, so only 8 different MHC I molecules are expressed .
2. For the same inbred UCLA mice described above, how many different types of
MHC II molecules will be expressed on the surface of APCs?
A) 0
B) 2
C) 3
D) 4
E) 6
Correct Answer: A
Rationale: The alpha and beta chains available cannot recombine with each other. I-Aα is
only compatible with I-Aβ, and I-Eβ is only compatible with I-Eα. These mice lack I-Eα
entirely, so no functional MHC II complexes can form .
3. Westwood mice are genetically manipulated and cannot produce TAP1 and
TAP2 proteins in any of their cells. What type of microorganisms will these animals
be susceptible to?
A) Extracellular bacteria only
B) Extracellular parasites only
C) Intracellular pathogens (viruses, intracellular bacteria)
D) Both extracellular and intracellular pathogens
E) None, they have normal immunity
Correct Answer: C
, Rationale: TAP1/TAP2 are required for transporting peptides from the cytosol into the
endoplasmic reticulum for loading onto MHC I molecules. Without TAP function, MHC I
cannot present endogenous antigens (viral or intracellular bacterial peptides) to CD8+ T
cells. Therefore, these mice are susceptible to intracellular pathogens .
4. The hybrid offspring between UCLA mice (no MHC II) and Westwood mice (no
TAP) will be able to:
A) Present antigen on MHC I only
B) Present antigen on MHC II only
C) Present antigen on both MHC I and MHC II
D) Not present antigen on either
Correct Answer: C
Rationale: The hybrid mice have functional MHC I (from UCLA inheritance of TAP genes)
and functional MHC II (from Westwood inheritance of MHC II genes). Both CD4+ and
CD8+ T cells can perform their immune functions .
5. You have two different male mice: Mouse 1 is homozygous for the k haplotype
(Dk, Lk, Kk, IAk, IEk). You mate Mouse 1 to a female (Mouse 3) that is H-2s
(homozygous for s haplotype). You take skin from a progeny and graft it onto
Mouse 1. Will the graft be rejected?
A) No, because the progeny is a close relative
B) Yes, because Mouse 1 lacks the s haplotype
C) No, because all MHC genes are identical
D) Yes, because of blood type incompatibility
, Correct Answer: B
Rationale: The progeny of Mouse 1 (kk) and Mouse 3 (ss) will be heterozygous (k/s) for the
MHC haplotypes. Mouse 1 is homozygous for the k haplotype and does not express any s
haplotype MHC molecules. The graft will be recognized as foreign and rejected .
6. In the same experiment, you graft the skin from the k/s heterozygous progeny
onto one of its siblings. Will the graft be rejected?
A) Yes, because the sibling may have different MHC
B) No, because all siblings share the same k/s haplotype
C) Yes, because of minor histocompatibility antigens
D) No, because the graft is from an offspring
Correct Answer: B
Rationale: When both parents are homozygous for different haplotypes (k and s), all F1
offspring are identical heterozygotes (k/s). All siblings will share exactly the same MHC
haplotypes. The graft will be recognized as "self" and will not be rejected .
7. Which fluorescence channel is typically used to detect MHC I expression in flow
cytometry?
A) Forward scatter (FSC)
B) Side scatter (SSC)
C) FITC (green fluorescence)
D) PE (red fluorescence)
Correct Answer: C
Answers | 2025 Revised Update | 100%
Correct - UCLA
SECTION 1: MHC STRUCTURE AND GENETICS
1. An inbred (syngeneic) strain of mice (UCLA mice) has the following MHC locus
organization: K, I-Aα, I-Aβ, I-Eα, I-Eβ, D, L, L. How many different types of MHC I
molecules will these mice express on the surface of their antigen-presenting cells
(APCs)?
A) 2
B) 4
C) 6
D) 8
E) 9
Correct Answer: D
Rationale: The MHC locus shows 9 genes total: K, I-Aα, I-Aβ, I-Eα, I-Eβ, D, L, L. The L gene
is duplicated. Since the mice are inbred, both maternal and paternal MHC I genes are
, identical. However, the duplicated L gene produces two identical proteins that are not
distinct, so only 8 different MHC I molecules are expressed .
2. For the same inbred UCLA mice described above, how many different types of
MHC II molecules will be expressed on the surface of APCs?
A) 0
B) 2
C) 3
D) 4
E) 6
Correct Answer: A
Rationale: The alpha and beta chains available cannot recombine with each other. I-Aα is
only compatible with I-Aβ, and I-Eβ is only compatible with I-Eα. These mice lack I-Eα
entirely, so no functional MHC II complexes can form .
3. Westwood mice are genetically manipulated and cannot produce TAP1 and
TAP2 proteins in any of their cells. What type of microorganisms will these animals
be susceptible to?
A) Extracellular bacteria only
B) Extracellular parasites only
C) Intracellular pathogens (viruses, intracellular bacteria)
D) Both extracellular and intracellular pathogens
E) None, they have normal immunity
Correct Answer: C
, Rationale: TAP1/TAP2 are required for transporting peptides from the cytosol into the
endoplasmic reticulum for loading onto MHC I molecules. Without TAP function, MHC I
cannot present endogenous antigens (viral or intracellular bacterial peptides) to CD8+ T
cells. Therefore, these mice are susceptible to intracellular pathogens .
4. The hybrid offspring between UCLA mice (no MHC II) and Westwood mice (no
TAP) will be able to:
A) Present antigen on MHC I only
B) Present antigen on MHC II only
C) Present antigen on both MHC I and MHC II
D) Not present antigen on either
Correct Answer: C
Rationale: The hybrid mice have functional MHC I (from UCLA inheritance of TAP genes)
and functional MHC II (from Westwood inheritance of MHC II genes). Both CD4+ and
CD8+ T cells can perform their immune functions .
5. You have two different male mice: Mouse 1 is homozygous for the k haplotype
(Dk, Lk, Kk, IAk, IEk). You mate Mouse 1 to a female (Mouse 3) that is H-2s
(homozygous for s haplotype). You take skin from a progeny and graft it onto
Mouse 1. Will the graft be rejected?
A) No, because the progeny is a close relative
B) Yes, because Mouse 1 lacks the s haplotype
C) No, because all MHC genes are identical
D) Yes, because of blood type incompatibility
, Correct Answer: B
Rationale: The progeny of Mouse 1 (kk) and Mouse 3 (ss) will be heterozygous (k/s) for the
MHC haplotypes. Mouse 1 is homozygous for the k haplotype and does not express any s
haplotype MHC molecules. The graft will be recognized as foreign and rejected .
6. In the same experiment, you graft the skin from the k/s heterozygous progeny
onto one of its siblings. Will the graft be rejected?
A) Yes, because the sibling may have different MHC
B) No, because all siblings share the same k/s haplotype
C) Yes, because of minor histocompatibility antigens
D) No, because the graft is from an offspring
Correct Answer: B
Rationale: When both parents are homozygous for different haplotypes (k and s), all F1
offspring are identical heterozygotes (k/s). All siblings will share exactly the same MHC
haplotypes. The graft will be recognized as "self" and will not be rejected .
7. Which fluorescence channel is typically used to detect MHC I expression in flow
cytometry?
A) Forward scatter (FSC)
B) Side scatter (SSC)
C) FITC (green fluorescence)
D) PE (red fluorescence)
Correct Answer: C
