MHCpræsentationen

MHCpræsentationen, also known as MHC presentation, refers to the process by which cells display fragments of proteins, called peptides, on their surface. This display is mediated by molecules called Major Histocompatibility Complex (MHC) proteins. These MHC molecules act like molecular billboards, presenting these peptide fragments to other cells, particularly immune cells. The MHC system is crucial for the immune system's ability to distinguish between self and non-self, and to identify and eliminate infected or abnormal cells.

There are two main classes of MHC molecules involved in this process: MHC class I and MHC class II. MHC class I molecules are found on almost all nucleated cells in the body and present peptides derived from proteins synthesized within the cell. This typically includes endogenous proteins, such as viral proteins during an infection or mutated proteins in cancer cells. When a cell presents a viral peptide on its MHC class I molecule, it signals to cytotoxic T lymphocytes (also known as killer T cells) that the cell is infected and should be destroyed.

MHC class II molecules are primarily found on specialized antigen-presenting cells (APCs), such as dendritic cells, macrophages, and B cells. These APCs engulf foreign material from their environment, process it into peptides, and then present these peptides on their MHC class II molecules. This presentation is then recognized by helper T lymphocytes, which orchestrate the adaptive immune response, including the activation of B cells to produce antibodies and the proliferation of cytotoxic T cells. The precise peptide displayed on the MHC molecule is determined by the structure of the MHC molecule itself and the specific protein from which the peptide is derived.