MHCpresenterade

MHCpresenterade is a term used to describe the function of Major Histocompatibility Complex (MHC) molecules in presenting antigens to T cells. MHC molecules are a group of genes that code for proteins found on the surface of cells in vertebrates. Their primary role is to display fragments of proteins, known as peptides, to T cells. This presentation is crucial for the immune system to recognize self from non-self, and to mount an appropriate response against foreign invaders like bacteria and viruses, or against abnormal self-cells like cancer cells.

There are two main classes of MHC molecules involved in antigen presentation: MHC class I and MHC class II. MHC class I molecules are found on almost all nucleated cells and present peptides derived from intracellular proteins. This includes normal cellular proteins as well as viral or tumor antigens produced within the cell. When a cytotoxic T cell (also known as a CD8+ T cell) recognizes a foreign peptide presented by MHC class I, it can initiate a cell-killing response.

MHC class II molecules, on the other hand, are primarily expressed on professional antigen-presenting cells (APCs) such as dendritic cells, macrophages, and B cells. These molecules present peptides derived from extracellular proteins that have been taken up by the APC through endocytosis. Helper T cells (also known as CD4+ T cells) recognize these peptides presented by MHC class II and, in turn, help to coordinate the immune response, often by activating B cells to produce antibodies or by enhancing the activity of cytotoxic T cells. The diversity of MHC genes within a population ensures that a wide range of antigens can be presented, contributing to the overall immune defense.