Krysspresentasjon

Krysspresentasjon, often translated as cross-presentation or cross-priming, is a crucial immunological process where antigens from extracellular sources are presented by antigen-presenting cells (APCs), typically dendritic cells, on MHC class I molecules. This allows for the activation of cytotoxic T lymphocytes (CTLs), which are responsible for recognizing and eliminating infected or cancerous cells.

Normally, MHC class I molecules present intracellular antigens derived from pathogens or self-proteins synthesized within the APC. However, krysspresentasjon enables APCs to acquire antigens from exogenous sources, such as viruses or tumor cells, and process them through the endogenous antigen presentation pathway. This is achieved through various mechanisms, including phagocytosis, endocytosis, and trogocytosis. Once internalized, the exogenous antigens are transported to the cytosol, where they can be processed by the proteasome and loaded onto MHC class I molecules.

This process is vital for initiating adaptive immune responses against extracellular pathogens that do not directly infect APCs, as well as for generating anti-tumor immunity. Dendritic cells are particularly adept at krysspresentasjon due to their specialized machinery for antigen uptake, processing, and cross-presentation. Understanding krysspresentasjon is fundamental for developing effective vaccines and immunotherapies.