Antigen-loaded but not unloaded CD1d-CD19 fusion activates murine iNKT cell functions in vivo. B6 mice were injected intraperitoneally with PBS44 (4 μg), αGC-loaded or unloaded CD1d-CD19 fusion (20 μg), or left untreated. After 2 (A) or 18 (B) hours, splenic and hepatic iNKT cells producing IFN-γ (A-B) or IL-4 (C) directly ex vivo were analyzed by intracellular cytokine staining and flow cytometry. Data are representative of 3 experiments with 1 to 2 mice analyzed per condition. Numbers in the histograms indicate MFI. (D) Serum was collected at different time points as indicated on the graphs and IFN-γ levels were measured by enzyme-linked immunosorbent assay. Data represent the mean ± SEM from 3 independent experiments for each time point indicated. Significance was determined by unpaired 2-tailed Student t test. *P < .05, **P < .01.