Major histocompatibility complex class II antigen presentation pathway via lysosomal acidification

The **lysosomal acidification pathway for MHC class II presentation** is a core immune process involving the endocytosis of extracellular proteins, their delivery to acidified late endosomes/lysosomes (also known as MHC class II compartments or MIICs), and proteolytic generation of antigenic peptides. Within these compartments, proteases (e.g., cathepsins) and thiol reductases (e.g., GILT) process proteins; the invariant chain guides MHC II molecules to these sites, is degraded, and replaced by antigenic peptides facilitated by HLA-DM. Peptide-loaded MHC II molecules are then transported to the cell surface for recognition by CD4^+^ T cells, driving adaptive immune responses and tolerance[2][3][8]. Disruption of any step (via drugs like chloroquine) impairs antigen presentation and immune function. This entry should not be considered a canonical, molecule-level drug target in biomedical databases, but rather a multi-component pathway. For structured data, list distinct actors (e.g., "Major histocompatibility complex class II (MHC II) receptor," "Cathepsin S," "Invariant chain") instead of this descriptive pathway phrase[2][3][8].

Other names

MHC class II antigen processing and presentation pathwayLysosomal MHC class II pathwayMIIC pathway (MHC class II compartment pathway)

Inhibitors of lysosomal acidification prevent antigen proteolysis and reduce MHC II presentation. Cathepsin inhibitors block protease activity necessary for peptide generation.