Enhanced CD1d phosphatidylserine presentation using a single-domain antibody promotes immunomodulatory CD1d-TIM-3...

Area of Science:

• Immunology
• Structural Biology
• Molecular Biology

Background:

• CD1d is a major histocompatibility complex class I-like molecule presenting lipid antigens.
• CD1d is expressed on various malignancies, making it a potential therapeutic target.
• Antibody targeting of CD1d on multiple myeloma cells may induce apoptosis.

Purpose of the Study:

• To investigate how a CD1d-specific single-domain antibody (VHH) affects annexin V binding to CD1d+ tumor cells.
• To elucidate the structural basis of VHH-CD1d interaction using X-ray crystallography.

Main Methods:

• In vitro cell-based assays and CRISPR-Cas9 gene editing were employed.
• X-ray crystallography was used to determine the structure of the VHH1D17-CD1d complex.
• Analysis of phosphatidylserine (PS) presentation and T-cell immunoglobulin and mucin domain containing (TIM) molecule interactions.

Main Results:

• The anti-CD1d VHH1D17 antibody enhances annexin V binding but does not induce apoptosis.
• VHH1D17 promotes phosphatidylserine (PS) presentation in CD1d, dependent on saposin.
• Structural analysis revealed VHH1D17 binds the A'-pocket of CD1d, exposing the lipid headgroup and enhancing PS presentation.
• CD1d-PS presentation enhances TIM-1 binding and induces TIM-3 signaling.

Conclusions:

• A novel CD1d(PS)-TIM axis involved in immune modulation was discovered.
• This axis has significant implications for immune regulation in physiological and pathological conditions.
• The findings offer new insights into CD1d-mediated immune responses beyond direct apoptosis induction.