Once captured, antigens are processed within APCs through two main pathways: the endogenous pathway and the exogenous pathway. The endogenous pathway involves the degradation of intracellular proteins by the proteasome, and the resulting peptides are loaded onto MHC class I molecules. The exogenous pathway, on the other hand, involves the uptake of extracellular proteins into endosomes or lysosomes, where they are processed and loaded onto MHC class II molecules.
