CD1 lipidomes reveal lipid-binding motifs and size-based antigen-display mechanisms

Area of Science:

• Immunology
• Structural Biology
• Biochemistry

Background:

• The CD1 system is crucial for presenting lipid antigens to T cells, playing a role in immune responses.
• Understanding the repertoire of self-lipids presented by CD1 molecules is essential for deciphering immune surveillance and autoimmune diseases.

Purpose of the Study:

• To map the self-lipidome presented by the four human CD1 molecules (CD1a, CD1b, CD1c, CD1d).
• To elucidate the structural basis for differential lipid binding and presentation by CD1 proteins.

Main Methods:

• Lipidomic analysis of CD1-lipid complexes.
• Structural determination of CD1 molecules bound to lipids.

Main Results:

• Over 2,000 CD1-lipid complexes were identified, demonstrating broad presentation of self-sphingolipids and phospholipids.
• Many lipids are presented in an unaltered form, unlike chemically processed peptide antigens.
• Distinct CD1 proteins exhibit specific lipid capture motifs based on lipid length and composition.
• CD1b uniquely accommodates two small lipids within its cleft due to a size mismatch with larger ligands.

Conclusions:

• The CD1 system displays a diverse range of self-lipids, with differential editing by each CD1 subtype.
• Lipid size and chemical properties dictate binding and presentation, suggesting general antigen display principles.
• The characterized CD1 lipidome aids in the discovery of novel T cell lipid antigens and blockers.