antigénprezentálást

Antigénprezentálás is a fundamental process in immunology that enables the adaptive immune system to recognize and respond to foreign invaders such as bacteria and viruses. It involves specialized cells, primarily antigen-presenting cells (APCs), which capture, process, and display fragments of these foreign substances, known as antigens, on their surface. The main types of APCs include dendritic cells, macrophages, and B cells.

Dendritic cells are particularly important as they are highly efficient at capturing antigens in peripheral tissues and migrating to lymph nodes to initiate immune responses. Macrophages engulf pathogens and cellular debris, also presenting antigens. B cells can bind to intact antigens via their B cell receptors and then internalize and present processed antigens.

The antigens are typically presented on the surface of APCs bound to molecules called major histocompatibility complex (MHC) proteins. There are two main classes of MHC molecules: MHC class I and MHC class II. Antigens derived from inside the cell, such as viral proteins synthesized within an infected cell, are usually presented on MHC class I molecules. Antigens derived from outside the cell, which have been engulfed by the APC, are typically presented on MHC class II molecules.

This presentation of antigens by MHC molecules is crucial for the activation of T lymphocytes. Naive T cells, which circulate in the body, can only recognize antigens when they are presented in this specific manner. Helper T cells recognize antigens presented on MHC class II, while cytotoxic T cells recognize antigens presented on MHC class I. This interaction triggers a cascade of events leading to the elimination of the pathogen or infected cell.