The autophagy machinery restrains iNKT cell activation through CD1D1 internalization

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• Invariant natural killer T (iNKT) cells are innate immune cells that recognize glycolipid antigens via CD1D molecules.
• Mechanisms controlling CD1D antigen presentation and iNKT cell activation in vivo remain incompletely understood.
• Autophagy is known to support antigen loading for CD4+ T cell immunity, but its role in iNKT cell activation is unclear.

Purpose of the Study:

• To investigate the role of autophagy in dendritic cell (DC)-mediated CD1D1 antigen presentation and iNKT cell activation.
• To elucidate the molecular mechanisms by which autophagy influences CD1D1 surface expression and iNKT cell stimulation.

Main Methods:

• Generated mice with DC-specific deletion of the autophagy gene Atg5.
• Assessed CD1D1-restricted glycolipid presentation in vivo.
• Measured iNKT cell cytokine production and bacterial loads during Sphingomonas paucimobilis infection.
• Investigated the role of clathrin-dependent endocytosis and AP2 complex in CD1D1 trafficking.

Main Results:

• DC-specific deletion of Atg5 improved CD1D1-glycolipid presentation in vivo.
• Enhanced iNKT cell cytokine production and reduced bacterial loads were observed in Atg5-deficient mice.
• Loss of Atg5 impaired clathrin-dependent internalization of CD1D1 via AP2, increasing surface expression of CD1D1-glycolipid complexes.
• Enhanced iNKT cell activation was independent of receptor-mediated uptake or costimulatory signals.

Conclusions:

• The autophagic machinery, through Atg5, negatively regulates CD1D1 surface expression by facilitating AP2-mediated internalization.
• Impaired autophagy in DCs leads to enhanced iNKT cell activation, contrasting with its supportive role in CD4+ T cell immunity.
• Targeting autophagy in DCs may represent a novel strategy to boost iNKT cell-based immunotherapies.