M cell-derived vesicles suggest a unique pathway for trans-epithelial antigen delivery

Area of Science:

• Immunology
• Cell Biology
• Microbiology

Background:

• M cells are specialized epithelial cells that transport antigens across mucosal barriers.
• Limited understanding exists regarding antigen transfer in the subepithelial zone.
• Tracking microparticles and transcytosed antigens presents significant challenges.

Purpose of the Study:

• To investigate antigen transfer mechanisms in the subepithelial zone.
• To identify and characterize novel vesicles involved in M cell antigen transport.
• To elucidate the role of M cell-derived vesicles in dendritic cell interactions.

Main Methods:

• Utilized transgenic reporter mice (dsRed for M cells, EGFP for myeloid cells).
• Observed M cell basolateral pocket interactions using microscopy.
• Characterized M cell-derived vesicles (MCM) and their uptake by dendritic cells.
• Analyzed MCM cargo content and regulation by bacterial transcytosis and TLR2 agonists.

Main Results:

• Identified M cell-derived vesicles (MCM) shed into the subepithelial space.
• MCM are taken up by specific dendritic cells (CX3CR1(+)CD11b(+) CD11c(+)).
• MCM preferentially colocalize with transcytosed bacteria, not polystyrene beads, in dendritic cells.
• MCM size and number increase with bacterial transcytosis and TLR2 agonist stimulation.

Conclusions:

• MCM represent a previously undescribed mechanism for antigen delivery from M cells to dendritic cells.
• MCM facilitate selective transfer of luminal contents, such as bacterial components, to the immune system.
• This pathway plays a dynamic role in mucosal immune surveillance and response during infection.