Antigen-loading compartments for major histocompatibility complex class II molecules continuously receive input from...

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• Major histocompatibility complex (MHC) class II molecules present antigens to CD4(+) T cells.
• Extracellular antigen uptake is the primary source for MHC class II ligands.
• The role of macroautophagy in delivering intracellular antigens for MHC class II presentation is not well understood.

Purpose of the Study:

• To investigate the constitutive role and efficacy of macroautophagy in delivering intracellular antigens for MHC class II presentation.
• To determine the functional relevance of this pathway in antigen presentation to CD4(+) T cells.

Main Methods:

• Demonstration of constitutive autophagosome formation in MHC class II-positive cells (dendritic, B, and epithelial cells).
• Observation of autophagosome fusion with MHC class II-loading compartments.
• Targeting of influenza matrix protein 1 to autophagosomes via Atg8/LC3 for enhanced MHC class II presentation analysis.

Main Results:

• Constitutive autophagosome formation and fusion with MHC class II compartments were observed in relevant antigen-presenting cells.
• Targeting intracellular antigens to autophagosomes significantly enhanced MHC class II presentation.
• Enhanced presentation led to a stronger stimulation of CD4(+) T cell clones.

Conclusions:

• Macroautophagy constitutively and efficiently delivers cytosolic proteins for MHC class II presentation.
• This pathway is functionally relevant for antigen presentation.
• Macroautophagy can be exploited to improve helper T cell stimulation and immune responses.