Structures of immunostimulatory natural glycolipids, α-GalCer and C-glycoside.

Strategies for the syntheses of plakoside A/αGalCer hybrid compounds SMC124 and EF77.

(A) A20 cells transfected with CD1d and pulsed with the indicated glycolipid concentrations were cultured with iNKT cell hybridoma 1.2 and IL-2 cytokine levels in the supernatant were quantified by ELISA after 16 h of culture. (B) Same as (A) except antigen presentation was carried out on plates coated with CD1d and incubated with the indicated glycolipids concentrations. (A and B) Similar results were obtained with additional iNKT cell hybridomas. (C) PBMCs were pulsed with 100 ng/ml of the indicated glycolipids and cultured overnight. Cells were washed and co-cultured with human iNKT cell lines for 24 h. Cytokine levels for human GM-CSF were measured in the supernatant using ELISA. Representative data from one of 3–5 experiments performed in triplicate wells using multiple human cell lines are shown. See also Figure S1.

C57Bl/6 mice were injected with 2 μg of the indicated antigen, and sera were analyzed at the indicated time points. (A and B) Serum samples were measured for cytokine levels by ELISA. Data are representative of 6 independent experiments of 2 or 3 mice per group. Error bars represent +/− SEM. (C and D) Mice were sacrificed at 22 h and TCRβ⁻, NK1.1⁺ natural killer cells were analyzed for the production of IFN-γ by intracellular cytokine staining. (C) Percentage of IFN-γ⁺ natural killer cells directly ex vivo 22 h post injection of lipid (open histogram) compared with PBS injected control (shaded histogram). Histograms are representative plots of a minimum of 3 independent experiments of 3–5 mice per group. Numbers represent percentage of IFN-γ⁺ natural killer cells. (D) MFI scatter plot of IFN-γ intracellular fluorescence from 3–5 mice per group. Data are representative of 4 independent experiments. (E) Serum samples were measured for IL-12p70 cytokine levels by ELISA. Data are representative of 2 independent experiments of 3 mice per group. Error bars represent +/− SEM. Statistically significant differences using the equal variance unpaired Student t test are indicated with an asterisk (*, p≤0.001) comparing αGalCer to either SMC124 or EF77. See also Figure S2.

(A) Plot of detergent resistance of CD1d/glycolipid/antibody complexes formed with SMC124, EF77, and known Th1- and Th2-biasing αGalCer agonists on JAWS II DCs. (B and C) C57Bl/6 mice were injected with 2 μg of the indicated lipid antigens and CD11c⁺ DCs were enriched using magnetic bead isolation at 2 (B) and 22 (C) h post injection. Varying number of enriched DCs were cultured with the 1.2 Vα14 iNKT cell hybridoma overnight and IL-2 in the supernatant quantified by ELISA. Data are plotted as the number of enriched DCs per well versus IL-2 (pg/ml). Data are representative of two independent experiments. Error bars represent +/− SEM of 2 or 3 mice per condition.

(A). Biacore sensorgram showing the binding of increasing concentrations of TCR (0.004 to 1 μM) to mouse CD1d-SMC124. (B). Overall structure of the ternary complex CD1d-SMC124-iNKT TCR. SMC124, yellow; CD1d heavy chain and β2-microglobulin chain, gray; TCR α chain, cyan; TCR β chain, orange. (C). Stereo image of the 2Fo–Fc electron density map of the ligand. The map is contoured at 1 σ and shown as a blue mesh around the ligand (in yellow) in side view with the α2 helix removed for the purpose of clarity. The cyclopropane modification on the sphingoid base is shown in green. See also Figure S3.

Top (A) and side (B) view of the SMC124-CD1d interactions. SMC124 is shown in yellow. The cyclopropane modification on the SMC124 sphingoid base is shown in green. Hydrogen bond interactions between CD1d residues and the polar moieties of SMC124 are indicated with blue dashed lines. (C and D) Contacts between SMC124 (C) and αGalCer (PDB ID 3HE6) (D) with the iNKT TCR. The conserved hydrogen bonds with residues on the CDR1α and CDR3α are shown as dashed blue lines with the corresponding distances indicated in Å. SMC124, yellow; αGalCer, orange; CD1d heavy chain, gray; TCR α chain, cyan. (E and F) Conformation of the sphingoid bases of SMC124 and αGalCer in the F′ pocket. (E) Top view of the CD1d binding groove. (F) Side view of the binding groove with the α2 helix removed for the purpose of clarity. SMC124 in yellow, αGalCer in orange. Note the more tightly packed conformation of the longer SMC124 sphingoid base in comparison to αGalCer. See also Figure S4 and Supplementary Tables 1 and 2.