Major Histocompatibility Complex (MHC) Molecules Quiz

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Questions and Answers

What is the significance of the polymorphic genes of MHC molecules?

Prevent autoimmune diseases

Increase the number of different MHC molecules that can present peptides to T cells (correct)

Allow for self-recognition by the immune system

Enhance the binding affinity of MHC molecules

Which cell type can be targeted by CD8+ CTLs due to the expression of MHC class 1 molecules?

All nucleated cells (correct)

Macrophages

Dendritic cells

B cells

What is the significance of co-dominant expression of MHC genes?

Reduces the risk of pathogen invasion

Enhances self-tolerance in the immune system

Promotes T cell differentiation

Increases diversity in the MHC repertoire (correct)

Which cell types interact with CD4+ helper T lymphocytes due to the expression of MHC class 2 molecules?

Dendritic cells, macrophages, and B cells Signup and view all the answers

What is the significance of codominant expression of HLA proteins?

It maximizes the number of peptides displayed by each individual Signup and view all the answers

Which cells mainly express class II molecules?

Dendritic cells, macrophages, and B lymphocytes Signup and view all the answers

Which cytokine can induce the expression of class II molecules on other cell types?

Interferon-γ Signup and view all the answers

How many polymorphic class I genes do humans have?

Three Signup and view all the answers

What is the term used for the set of MHC genes present on each chromosome?

MHC haplotype Signup and view all the answers

Why are siblings often tested before unrelated individuals for their suitability as donors for transplantation?

The chance of finding an HLA match with the recipient is much greater for siblings Signup and view all the answers

How are individual alleles designated in the modern terminology?

Based on molecular typing Signup and view all the answers

What do the peptide-binding clefts of MHC molecules bind?

Peptides derived from protein antigens Signup and view all the answers

How many peptides can each MHC molecule present at a time?

1 Signup and view all the answers

What is essential for the antigen display function of MHC molecules?

Broad specificity for peptide binding Signup and view all the answers

Why can MHC-restricted CD4+ T cells and CD8+ T cells recognize protein antigens?

Protein antigens have the structural and charge characteristics that permit binding to the clefts of MHC molecules Signup and view all the answers

Study Notes

Significance of Polymorphic Genes of MHC Molecules

Polymorphic genes enhance the diversity of MHC molecules, allowing for a broad range of antigen presentation.
Increased diversity improves the immune system's ability to recognize and respond to various pathogens.

Target Cell Types for CD8+ CTLs

CD8+ cytotoxic T lymphocytes (CTLs) target cells that express MHC class I molecules, typically found on all nucleated cells.
This interaction is crucial for the elimination of virus-infected or malignant cells.

Co-Dominant Expression of MHC Genes

Co-dominant expression ensures that both inherited alleles from parents are expressed, increasing the variety of MHC molecules on the surface of cells.
This maximizes the potential for antigen presentation to T cells, enhancing immune response effectiveness.

Cell Types Interacting with CD4+ Helper T Lymphocytes

CD4+ helper T lymphocytes interact primarily with cells presenting MHC class II molecules, commonly found on antigen-presenting cells (APCs) such as dendritic cells, macrophages, and B cells.
This interaction is critical for activating the adaptive immune response.

Significance of Codominant Expression of HLA Proteins

Codominant expression of human leukocyte antigen (HLA) proteins allows for the presentation of a more diverse array of peptides to T cells, improving immune vigilance and responses to infections.

Cells Expressing Class II Molecules

Class II MHC molecules are mainly expressed on professional antigen-presenting cells, including dendritic cells, macrophages, and B cells.
These cells play a pivotal role in initiating and regulating immune responses.

Cytokine Inducing Class II Molecule Expression

Interferon-gamma (IFN-γ) is a cytokine that can induce the expression of MHC class II molecules on non-classical APCs, broadening their ability to present antigens.

Number of Polymorphic Class I Genes in Humans

Humans possess multiple polymorphic class I genes, specifically HLA-A, HLA-B, and HLA-C, each contributing to the diversity of MHC class I molecules.

Terminology for MHC Gene Set

The set of MHC genes present on each chromosome is referred to as the Major Histocompatibility Complex (MHC) haplotype, representing a collection of genes inherited together.

Sibling Testing for Transplantation

Siblings are often tested for compatibility as organ donors before unrelated individuals due to the higher probability of genetic matching and reduction of transplant rejection risks.

Modern Designation of Individual Alleles

Individual alleles of MHC genes are designated according to a numerical system that includes the gene name followed by an asterisk and the specific allele number (e.g., HLA-DRB1*01).

Peptide-Binding Cleft Function

The peptide-binding clefts of MHC molecules bind to specific peptides derived from protein antigens, facilitating T cell recognition.

Peptide Presentation Capacity

Each MHC molecule can present a single peptide at a time to T cells, a crucial step for the activation of an adaptive immune response.

Essential Component for Antigen Display Function

Proper folding and stable binding of peptides in the MHC molecule's cleft are essential for its antigen display function.

Recognition of Protein Antigens by T Cells

MHC-restricted CD4+ and CD8+ T cells recognize protein antigens due to the specific presentation of peptide fragments in the context of MHC molecules, linking innate and adaptive immunity.

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Description

Test your knowledge on the properties and significance of MHC molecules and genes, including their role in immune responses and interaction with CTLs. Explore the polymorphic genes and their impact on presenting and responding to microbial peptides.