Pathways for the processing and presentation of antigens to T cells

Area of Science:

• Immunology
• Molecular Biology
• Cell Biology

Background:

• Vertebrate cells utilize distinct pathways for peptide antigen presentation to T cells.
• The endogenous pathway involves MHC class I molecules and CD8+ T cells, processing intracellular proteins.
• The exogenous pathway involves MHC class II molecules and CD4+ T cells, processing extracellular antigens.

Purpose of the Study:

• To elucidate the mechanisms of peptide generation and presentation by the endogenous and exogenous pathways.
• To investigate the role of specific molecules in antigen processing and T cell recognition.

Main Methods:

• The study focuses on the molecular components and processes involved in antigen processing.
• Key elements include proteasomes, the ubiquitin pathway, peptide transporters (TAP), and endosomal/lysosomal degradation.

Main Results:

• The endogenous pathway utilizes proteasomes and the transporter associated with antigen processing (TAP) for peptide generation and endoplasmic reticulum entry.
• The exogenous pathway involves endocytosis, lysosomal degradation, and requires a molecule like H-2M (mouse) or HLA-DM (human) for MHC class II loading, though its exact function remains unclear.
• The MHC class II region contains genes crucial for antigen processing, including proteasome subunits (LMP2, LMP7), TAP subunits (TAP1, TAP2), and the H-2M/HLA-DM molecule (DMA, DMB).

Conclusions:

• Two distinct cellular pathways, endogenous and exogenous, are essential for T cell-mediated immunity.
• Understanding these pathways, including the role of MHC class II-associated molecules, is critical for comprehending immune responses.