Antigeenverwerkingspaden

The antigen-processing pathways break down antigens for presentation to lymphocytes.

The endogenous and exogenous pathways are the two main antigen-processing pathways.

The endogenous pathway involves MHC I molecules and processes antigens from within the cell, typically those produced by viruses and abnormal tumor proteins.

Within the cell, the proteasome degrades these intracellular antigenic proteins into peptide fragments.

These fragments bind to the newly synthesized MHC I molecules within the ER, creating MHC I-antigen complexes, which are then inserted into the cell membrane.

In contrast, antigen-presenting cells, such as the dendritic cells equipped with MHC II molecules, participate in the exogenous pathway.

These APCs ingest and enclose pathogens, such as bacteria and fungi, in phagosomes or endosomes that fuse with lysosomes.

Next, the pathogen is enzymatically degraded into smaller antigenic fragments.

Simultaneously, the ER secretes vesicles carrying MHC II molecules, which fuse with the vesicles carrying the antigen fragments.

The foreign peptides then bind MHC II to form the MHC II-peptide complex, which is then expressed on the cell membrane.