Immunology Quiz- Major Histocompatibility Complex (Mhc)

MHC class II genes are responsible for encoding the proteins that play a crucial role in the immune system by presenting antigens to T cells. The MHC class II region contains three major loci: HLA-DP, HLA-DQ, and HLA-DR. Each locus consists of two subunits, alpha and beta, resulting in a total of six genes. Therefore, the correct answer is 6 (HLA-DP alpha/beta, HLA-DQ alpha/beta, HLA-DR alpha/beta).

DR2 is associated with Goodpasture's syndrome.

Class II MHC molecules accommodate larger peptides and thus would be referred to analogously as a "hotdog in a bun", in contrast to class I MHC molecules.

Class III MHC genes encode for complement molecules. The complement system is an important part of the immune system that helps to recognize and eliminate pathogens. Complement molecules play a role in the activation and regulation of the complement system, which includes a cascade of proteins that can destroy pathogens directly or enhance the immune response. These molecules are not directly involved in the activation of CD4+ or CD8+ T cells or the production of cytokine molecules.

MHC molecules exhibit co-dominant expression, meaning that both alleles of the MHC gene are expressed and contribute to the overall MHC molecule. On the other hand, immunoglobulin/TCR molecules exhibit allelic exclusion, which means that only one allele of the immunoglobulin/TCR gene is expressed in each B or T cell, resulting in the production of a single type of immunoglobulin/TCR molecule.

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Certain MHC haplotypes, such as B27, are associated with autoimmune diseases like Ankylosing spondylitis. This means that individuals who have the B27 haplotype are more likely to develop Ankylosing spondylitis compared to those who do not have this haplotype.

The correct answer is DR3. Certain MHC haplotypes, specifically the HLA-DR3 haplotype, have been found to be associated with an increased risk of developing systemic lupus erythematosus, an autoimmune disease. The HLA-DR3 haplotype is a genetic variant of the HLA-DR gene, which plays a role in the immune system's recognition of self and non-self antigens. This association suggests that individuals carrying the DR3 haplotype may have a genetic predisposition to developing systemic lupus erythematosus.

The correct order from most alleles (most polymorphic) to least alleles is B > A > C. This means that HLA-B has the highest number of alleles, followed by HLA-A, and then HLA-C.

Because of a lack of genetic recombination in the MHC (Major Histocompatibility Complex), blocks of alleles (haplotypes) are inherited together, and they are identical in families. This is likely to result in:



Family members have identical combinations of HLA alleles thus tissue transplantation is difficult.



The lack of genetic recombination in the MHC means that family members are more likely to have the same HLA (Human Leukocyte Antigen) alleles, which can complicate tissue transplantation due to the increased risk of graft rejection.

The correct answer is DR4 because certain MHC haplotypes, including DR4, have been found to be associated with autoimmune diseases such as Pemphigus vulgaris. This suggests that individuals with the DR4 HLA type may have a higher risk of developing Pemphigus vulgaris compared to those with other HLA types.

The DR beta gene has the most alleles and is the most polymorphic among the MHC class II genes. This means that there are more variations and diversity in the DR beta gene compared to the other MHC class II genes listed.

The correct answer is "Disadvantage; Increase." The evidence mentioned in the passage suggests that homozygosity at HLA class I is advantageous with respect to HIV/AIDS, meaning that it provides some form of protection or advantage. On the other hand, homozygosity at HLA class II is associated with an increase in the risk of hepatitis B virus infection persisting, indicating a disadvantage.

DR alpha has the least alleles among the given MHC class II genes. This means that there are fewer variations or variants of the DR alpha gene compared to the other genes mentioned. The alleles of MHC class II genes play a crucial role in immune responses and antigen presentation, so having fewer alleles of DR alpha may indicate a lower level of genetic diversity or variability in this particular gene compared to the others.

Certain MHC haplotypes, such as DR4, are associated with autoimmune diseases like Rheumatoid arthritis. This means that individuals who possess the DR4 HLA type are more likely to develop Rheumatoid arthritis compared to those who do not have this haplotype.

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Certain MHC haplotypes are associated with autoimmune diseases, including multiple sclerosis. In this case, the correct answer is DR2, which is a specific HLA type that has been found to be associated with an increased risk of developing multiple sclerosis.