Antigen processing and presentation via MHC Class II molecules orchestrates immune responses by facilitating the detection and elimination of extracellular pathogens. The process begins with phagocytosis and culminates in the transport of peptide-loaded MHC Class II molecules to the plasma membrane, ultimately enabling the immune system to combat foreign antigens and pathogens. Understanding this process is crucial for developing immunotherapy and vaccines.

Antigen processing via MHC Class I molecules is essential for the immune response, involving proteasomal degradation, peptide loading in the ER, transport to the cell surface, and presentation to CD8+ T cells. This process enables surveillance and elimination of abnormal cells, crucial for understanding immune responses and developing immunotherapies against diseases like cancer.

Endogenous antigens originate within the cell and are presented to CD8+ T cells via MHC Class I, eliciting immune responses against infected or abnormal cells. Exogenous antigens, from outside the cell, are presented to CD4+ T cells via MHC Class II, stimulating immune responses. This process is essential for fighting infections and abnormal cells.