Mhc Structure And Function
Feldman lecture 9/23/08
Questions and Answers
- 1.
The phenomenon whereby a T cell can only recognize a peptide antigen when it is bound to a particular MHC molecule is called
- A.
Dominance
- B.
Professional antigen recognition
- C.
MHC restriction
- D.
Positive selection
- E.
Negative selection
Correct Answer
C. MHC restrictionExplanation
MHC restriction refers to the phenomenon where a T cell can only recognize a peptide antigen when it is bound to a specific MHC molecule. This is because T cells have T cell receptors (TCRs) that can only recognize antigens when they are presented on MHC molecules. MHC molecules play a crucial role in presenting antigens to T cells, allowing them to initiate an immune response against foreign substances. Therefore, MHC restriction is essential for ensuring that T cells only respond to antigens that are presented on the appropriate MHC molecules.Rate this question:
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- 2.
True or False: An antigen that binds to a specific B cell receptor only has one epitope.
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
Each B-cell receptor actually has multiple epitopes. All epitopes will be internalized when one binds and since they are chopped up inside the cell, all of them will be presented on MHC II molecules. This is the basis for the conjugate vaccine.Rate this question:
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- 3.
B cell responses to bacterial polysaccharides do not require peptide-specific T-cell help and thus are called:
- A.
Innate immune responses
- B.
TI-2 antigens
- C.
TI-4 antigens
- D.
TNF-alpha mediated responses
- E.
INF-gamma mediated repsonses
Correct Answer
B. TI-2 antigensExplanation
B cell responses to bacterial polysaccharides do not require peptide-specific T-cell help and thus are called TI-2 antigens. This means that B cells can directly recognize and respond to these antigens without the need for T-cell assistance. TI-2 antigens can stimulate B cells to produce antibodies, leading to an immune response against the bacterial polysaccharides. This is different from TI-4 antigens, which require T-cell help, and the TNF-alpha and INF-gamma mediated responses, which involve different immune mechanisms.Rate this question:
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- 4.
Two examples of conjugate vaccines are
- A.
H.influenzae and HPV
- B.
H.influenzae and S.pneumoniae
- C.
MMR and HPV
- D.
MMR and H.influenzae
- E.
Rotavirus and HPV
Correct Answer
B. H.influenzae and S.pneumoniaeExplanation
Conjugate vaccines are vaccines that use a part of the bacteria or virus, such as a protein or sugar, to stimulate an immune response. In this case, the correct answer is H.influenzae and S.pneumoniae. H.influenzae and S.pneumoniae are both bacteria that can cause serious infections, particularly in young children. Conjugate vaccines for these bacteria have been developed to help prevent these infections. MMR (measles, mumps, and rubella) and HPV (human papillomavirus) are not examples of conjugate vaccines. Rotavirus is a virus, not a bacteria, and does not have a conjugate vaccine.Rate this question:
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- 5.
True or False: MHC class molecules rearrange
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
MHC class molecules do not rearrange. MHC class molecules are proteins found on the surface of cells that play a crucial role in the immune system by presenting antigens to T cells. While MHC class I molecules are constantly present on the surface of cells, MHC class II molecules are only expressed when the cell is activated by an immune response. However, neither MHC class I nor MHC class II molecules undergo rearrangement. They are encoded by specific genes and their structure remains constant.Rate this question:
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- 6.
All MHC class I and MHC class II genes are ______________ on a cell.
Correct Answer
co-expressed
coexpressed
expressedExplanation
MHC class I and MHC class II genes are expressed on a cell. This means that both types of genes are actively producing their respective proteins, which are important for the immune system. The term "co-expressed" or "coexpressed" implies that these genes are expressed together or simultaneously, indicating that both MHC class I and MHC class II genes are active in the cell. Therefore, the correct answer is "co-expressed," "coexpressed," or simply "expressed."Rate this question:
- 7.
MHC makes it difficult for pathogens by being
- A.
Polygenic
- B.
Polymorphic
- C.
Polyvalent
- D.
A and B
- E.
B and C
Correct Answer
D. A and BExplanation
The correct answer is A and B. MHC (major histocompatibility complex) makes it difficult for pathogens by being polygenic, meaning that it has multiple genes that code for different MHC molecules, increasing the diversity of antigens that can be recognized. MHC is also polymorphic, meaning that there are multiple alleles for each MHC gene, further increasing the diversity of antigens that can be recognized. This diversity makes it challenging for pathogens to evade the immune system. Polyvalent (option C) is not a characteristic of MHC and therefore not a correct answer.Rate this question:
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- 8.
We have ______ MHC I genes.
Correct Answer
six
6Explanation
We have six MHC I genes. The MHC I genes code for proteins that are found on the surface of cells and play a crucial role in the immune system by presenting antigens to T cells. These genes are highly polymorphic, meaning they have multiple variants, which allows for a diverse range of antigens to be presented. The number six indicates the specific count of MHC I genes present in our system.Rate this question:
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