Generation of functional NKT cells in vitro from embryonic stem cells bearing rearranged invariant Valpha14-Jalpha18 TCRalpha gene.

Establishment of a system with efficient generation of natural killer T (NKT) cells from embryonic stem (ES) cells would enable us to identify the cells with NKT-cell potential and obtain NKT cells with desired function. Here, using cloned ES (NKT-ES) cells generated by the transfer of nuclei from mature NKT cells, we have established a culture system that preferentially developed functional NKT cells and also identified early NKT progenitors, which first appeared on day 11 as a c-kit(+) population in the cocultures on OP9 cells with expression of Notch ligand, delta-like1 (OP9/Dll-1) and became c-kit(lo/-) on day 14. Interestingly, in the presence of Notch signals, NKT-ES cells differentiated only to thymic CD44(lo) CD24(hi) NKT cells producing mainly interleukin-4 (IL-4), whereas NKT cells resembling CD44(hi) CD24(lo) liver NKT cells producing mainly interferon gamma (IFN-gamma) and exhibiting strong adjuvant activity in vivo were developed in the switch culture starting at day 14 in the absence of Notch. The cloned ES culture system offers a new opportunity for the elucidation of the molecular events on NKT-cell development and for the establishment of NKT-cell therapy.

A novel subset of mouse NKT cells bearing the IL-17 receptor B responds to IL-25 and contributes to airway hyperreactivity.

Airway hypersensitive reaction (AHR) is an animal model for asthma, which is caused or enhanced by environmental factors such as allergen exposure. However, the precise mechanisms that drive AHR remain unclear. We identified a novel subset of natural killer T (NKT) cells that expresses the interleukin 17 receptor B (IL-17RB) for IL-25 (also known as IL-17E) and is essential for the induction of AHR. IL-17RB is preferentially expressed on a fraction of CD4(+) NKT cells but not on other splenic leukocyte populations tested. IL-17RB(+) CD4(+) NKT cells produce predominantly IL-13 and Th2 chemokines upon stimulation with IL-25 in vitro. IL-17RB(+) NKT cells were detected in the lung, and depletion of IL-17RB(+) NKT cells by IL-17RB-specific monoclonal antibodies or NKT cell-deficient Jalpha18(-/-) mice failed to develop IL-25-dependent AHR. Cell transfer of IL-17RB(+) but not IL-17RB(-) NKT cells into Jalpha18(-/-) mice also successfully reconstituted AHR induction. These results strongly suggest that IL-17RB(+) CD4(+) NKT cells play a crucial role in the pathogenesis of asthma.

PDC-TREM, a plasmacytoid dendritic cell-specific receptor, is responsible for augmented production of type I interferon.

Type I interferons (IFNs) derived from plasmacytoid dendritic cells (PDCs) are critical for antiviral responses; however, the mechanisms underlying their production remain unclear. We have identified a receptor, PDC-TREM, which is associated with Plexin-A1 (PlxnA1) on the PDC cell surface and is preferentially expressed after TLR-stimulation. Limited TLR signals induced PDC-TREM expression but failed to induce IFN-alpha production. However, when coupled with Sema6D, a ligand for Plexin-A1, limited TLR-stimulation resulted in PDC-TREM-mediated DAP12-dependent phosphorylation of phosphoinositide 3-kinase (PI3K) and extracellular regulated kinase (Erk) 1/2 at 6-9 h, and IFN-alpha was produced. Inhibition of PDC-TREM expression by pdctrem-shRNA, blocking of PDC-TREM-binding with PlxnA1 by PDC-TREM mAb, and DAP12 deficiency all resulted in greatly reduced PDC-TREM-dependent activation of signaling molecules and IFN-alpha production. Thus, PDC-TREM is responsible for IFN-alpha production, whereas TLR signals are essential for PDC-TREM expression.