MHCmolekyyleihin

MHCmolekyyleihin, or Major Histocompatibility Complex (MHC) molecules, are a group of proteins found on the surface of most nucleated cells. They play a crucial role in the immune system by presenting antigens to T cells, which are a type of white blood cell. The MHC system is highly polymorphic, meaning it exists in many different forms, which is why it is often referred to as the "histocompatibility" complex. This polymorphism allows the immune system to distinguish between self and non-self antigens, which is essential for the body's defense against pathogens.

The MHC system is divided into two main classes: MHC class I and MHC class II. MHC class I molecules are found on the surface of almost all nucleated cells and present intracellular antigens to CD8+ T cells. These antigens are typically derived from proteins that have been broken down inside the cell. MHC class II molecules, on the other hand, are found on the surface of professional antigen-presenting cells (APCs) such as dendritic cells and B cells, and present extracellular antigens to CD4+ T cells. These antigens are typically derived from extracellular proteins that have been taken up by the APC.

The MHC system is also involved in other immune responses, such as natural killer (NK) cell activity and the regulation of immune responses. Defects in the MHC system can lead to immune disorders, such as autoimmune diseases and certain types of cancer. The study of MHC molecules is an active area of research in immunology, with ongoing efforts to understand their structure, function, and role in health and disease.