MHCmolekulákra

MHCmolekulákra refers to MHC molecules, which are a group of cell surface proteins essential for the vertebrate immune system. They are also known as Human Leukocyte Antigens (HLA) in humans. MHC molecules are responsible for presenting peptide fragments to T cells, thereby initiating an adaptive immune response. There are two main classes of MHC molecules: Class I and Class II.

MHC Class I molecules are found on the surface of almost all nucleated cells in the body. They primarily present peptides derived from intracellular proteins, such as viral proteins or self-proteins, to cytotoxic T lymphocytes (CTLs), also known as CD8+ T cells. This presentation signals to the CTLs whether a cell is infected or abnormal, leading to its destruction.

MHC Class II molecules are expressed on professional antigen-presenting cells (APCs), including dendritic cells, macrophages, and B cells. They present peptides derived from extracellular proteins that have been taken up by the APC through phagocytosis or endocytosis. These peptides are presented to helper T lymphocytes (T helper cells), also known as CD4+ T cells, which then orchestrate the immune response by activating other immune cells.

The genes encoding MHC molecules are highly polymorphic, meaning there are many different versions of these genes within a population. This genetic diversity is crucial for the survival of a species, as it increases the likelihood that at least some individuals will be able to present a wide range of pathogen-derived peptides and mount an effective immune response. MHC molecules play a vital role in organ transplantation, as mismatched MHC molecules between donor and recipient can lead to immune rejection.