The Major Histocompatibility Complex and Antigen Processing and Presentation, biology homework help

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The Major Histocompatibility Complex and Antigen Processing and Presentation.

1. Explain this statement: “T lymphocytes are MHC-restricted”.

2. Briefly describe the role of antigen-presenting cells.

3. Are Class I and Class II MHC monospecific or multispecific? Explain.

4. Which human cells express MHC class I and which human cells express MHC class II?

5. Briefly describe – or diagram – the structures of MHC class I and MHC class II molecules. Be sure to indicate where the antigens bind, as well as which portion of the molecule interacts with the T lymphocyte accessory molecules.

6. Which T lymphocytes recognize MHC class I versus MHC class II molecules? How are CD4 and CD8 involved in MHC restriction during antigen-presentation? Give a specific answer for both CD4 and CD8, and make a drawing to show these mechanisms.

7. Briefly discuss the inheritance patterns of MHC class I and class II molecules. In humans, there are 3 Class I loci (HLA-A, HLA-B, HLA-C), and 3 Class II loci (HLA-DP, HLA-DQ, HLA-DR). However, there are over 3 times as many Class II antigens than Class I antigens that are expressed on heterozygous cells. What is the primary reason for this?

8. Briefly describe two ways in which expression of MHC molecules is controlled.

9. It is recognized that heterozygosity at the Class I and Class II loci imparts immune advantages because individuals can present a wider array of antigens than homozygotes. Although heterozygotes possess a diverse set of MHC antigens (over 20 different Class I and Class II antigens), this number is by no means extensive. It would seem to be beneficial to the human race if there was more diversity in MHC antigens since this would increase the number of antigens an individual could present. However, this is not the case. Why do you think the diversity of MHC antigens is somewhat limited? What benefit does it serve to have this limited diversity of MHC antigens?

10. Describe the mixed leukocyte reaction (MLR; also called the mixed lymphocyte reaction). What is the basic protocol, and how is this used to identify MHC antigens?

11. Briefly describe – or diagram – the exogenous or endocytic pathway for antigen presentation. Be sure to include a discussion of the accessory proteins involved in the pathway.

12. Briefly explain why endogenous antigens are prevented from being presented via the exogenous pathway, and vice versa.

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