antigénfeldolgozást

Antigénfeldolgozás is a Hungarian term that translates to antigen processing in English. It refers to the complex cellular mechanisms by which foreign proteins, or antigens, are broken down into smaller fragments, called peptides, that can then be presented on the surface of cells. This presentation is crucial for the immune system, particularly for T cells, to recognize and respond to foreign invaders like bacteria, viruses, or cancerous cells.

The process typically begins when a cell encounters an antigen. For antigens that enter the cell, such as viruses, they are processed within the cytoplasm by proteasomes, which are large protein complexes that degrade other proteins. The resulting peptides are then transported into the endoplasmic reticulum. For antigens that are taken up from outside the cell, such as by phagocytosis, they are typically processed within specialized organelles called lysosomes.

Once inside the endoplasmic reticulum or lysosomes, these peptide fragments are loaded onto molecules called Major Histocompatibility Complex (MHC) proteins. There are two main classes of MHC proteins: MHC class I and MHC class II. MHC class I molecules present peptides derived from intracellular antigens (like viral proteins) to cytotoxic T lymphocytes (killer T cells), while MHC class II molecules present peptides derived from extracellular antigens (like bacterial proteins) to helper T lymphocytes. This presentation of antigen-MHC complexes on the cell surface acts as a signal to the immune system, initiating an adaptive immune response.