keresztprezentációra

Keresztprezentációra, a Hungarian term, translates to "cross-presentation" in English. This term primarily refers to a biological process where antigen-presenting cells (APCs), such as dendritic cells, present antigens that are not of their own origin to T helper cells.

This process is crucial for initiating adaptive immune responses, particularly against exogenous antigens, which are antigens from outside the APC itself. In a typical scenario, APCs internalize pathogens or foreign substances through phagocytosis or endocytosis. These internalized antigens are then processed within the APC. For cross-presentation to occur, these processed exogenous antigens are somehow transferred to the MHC class I pathway, a pathway usually reserved for endogenous antigens (proteins produced within the APC).

Once loaded onto MHC class I molecules, these exogenous antigens are displayed on the surface of the APC. This presentation is then recognized by cytotoxic T lymphocytes (CTLs), which are normally activated by endogenous antigens. By presenting exogenous antigens on MHC class I, APCs can effectively prime CTLs to recognize and eliminate infected cells or tumor cells that are displaying these same foreign antigens. This mechanism is vital for generating immunity against viruses that do not directly infect APCs and for orchestrating anti-tumor immunity.