Major Histocompatibility Complexes (MHC)

Definition

Major Histocompatibility Complexes (MHC) are a group of genes that encode cell surface proteins responsible for the recognition of self and non-self molecules, playing a crucial role in the immune system's ability to distinguish between the body's own cells and foreign invaders.

5 Must Know Facts For Your Next Test

1. MHC molecules are divided into two main classes: MHC class I and MHC class II, which have distinct functions in the immune response.
2. MHC class I molecules present peptides derived from intracellular proteins, including those from viruses and cancer cells, to CD8+ T cells, which can then destroy the infected or cancerous cells.
3. MHC class II molecules present peptides derived from extracellular proteins, such as those from bacteria and parasites, to CD4+ T cells, which can then coordinate the appropriate immune response.
4. The high degree of genetic diversity in the MHC genes allows for the recognition of a wide range of foreign antigens, enhancing the immune system's ability to respond to a variety of pathogens.
5. Antigen-presenting cells, such as dendritic cells, macrophages, and B cells, play a crucial role in the immune response by displaying MHC-antigen complexes to T cells.

Review Questions

• Explain the role of MHC molecules in the immune system's ability to distinguish self from non-self.
  • MHC molecules are essential for the immune system's ability to recognize and respond to foreign antigens. MHC class I molecules display peptides derived from intracellular proteins, including those from viruses and cancer cells, to CD8+ T cells, which can then destroy the infected or cancerous cells. MHC class II molecules display peptides derived from extracellular proteins, such as those from bacteria and parasites, to CD4+ T cells, which can then coordinate the appropriate immune response. The high genetic diversity of the MHC genes allows for the recognition of a wide range of foreign antigens, enhancing the immune system's ability to respond to a variety of pathogens and maintain self-tolerance.
• Describe the function of antigen-presenting cells in the context of MHC-mediated immune responses.
  • Antigen-presenting cells, such as dendritic cells, macrophages, and B cells, play a crucial role in the immune response by displaying MHC-antigen complexes to T cells. These cells internalize and process foreign antigens, then display peptide fragments derived from these antigens on their surface in the context of MHC molecules. The MHC-antigen complexes are recognized by T cell receptors, triggering an immune response. Antigen-presenting cells are essential for initiating and coordinating the adaptive immune response, as they bridge the gap between the innate and adaptive immune systems.
• Analyze the significance of the high genetic diversity observed in the MHC gene complex and its impact on the immune system's ability to respond to a wide range of pathogens.
  • The high degree of genetic diversity in the MHC gene complex is a critical feature that enhances the immune system's ability to recognize and respond to a wide range of foreign antigens. This diversity is generated through the combination of multiple alleles at each MHC locus, as well as the potential for gene recombination and mutation. The resulting MHC polymorphism allows for the presentation of a vast array of peptide fragments to T cells, increasing the chances of recognizing and mounting an effective immune response against a diverse array of pathogens. This genetic diversity is a key evolutionary adaptation that enables the immune system to adapt and respond to the constantly changing landscape of infectious agents, ultimately improving the chances of survival for the host organism.

Related terms

Antigen Presentation: The process by which cells display foreign antigens on their surface, allowing them to be recognized and targeted by the immune system.

T Cell Receptor (TCR): A receptor molecule found on the surface of T cells that recognizes and binds to MHC-antigen complexes, triggering an immune response.

Immune Surveillance: The continuous monitoring of the body's cells by the immune system to detect and eliminate any abnormal or foreign cells.