Major Histocompatibility Complex (MHC) Classes .The Major Histocompatibility Complex (MHC) is a group of genes that play a crucial role in the immune system. These genes encode proteins that present antigens (foreign substances) to T cells, triggering an immune response. MHC genes are highly polymorphic, meaning they have many different versions or alleles, contributing to individual variation in immune response.
There are three main classes of MHC molecules
1.MHC class (1);
Found on the surface of most nucleated cells.
Present antigens derived from intracellular pathogens (like viruses and bacteria) to CD8+ cytotoxic T cells.
These T cells then eliminate infected cells.
2.MHC class (2);
Primarily found on antigen-presenting cells (APCs) such as macrophages, dendritic cells, and B cells.
Present antigens derived from extracellular pathogens (like bacteria and parasites) to CD4+ helper T cells.
These T cells then coordinate the immune response by activating other immune cells.
3.MHC class (3);
Encode proteins involved in the immune response but do not directly present antigens.
These proteins include complement components, tumor necrosis factor (TNF), and other inflammatory cytokines.
Importance of MHC
🔹Immune response: MHC molecules are essential for recognizing and responding to foreign antigens.
🔹Tissue transplantation: MHC molecules are involved in tissue compatibility and rejection.
🔹Disease susceptibility: Certain MHC alleles are associated with increased susceptibility to autoimmune diseases and infectious diseases.
🔹Understanding MHC molecules is crucial for understanding the immune system and developing strategies for preventing and treating diseases.
