TLR stimulation of type II NKT cells requires cell to cell contact with DCs with involvement of CD40-CD40L and IL-12p40 (INC6P.318)

Abstract

Abstract Natural killer T (NKT) cells are CD1d restricted innate like lymphocytes recognizing lipid antigens and mediating immune regulatory functions. NKT cells are divided into two subsets based on the type of T cell receptor (TCR) expressed. Type 1 or invariant NKT cells uses an invariant TCRα-chain (Vα14-Jα18 in mice/Vα24-Jα18 in humans) and type II or diverse NKT cells are all non Vα14 expressing NKT cells. Most of the knowledge about NKT cells have been derived from type I NKT cells, while type II NKT cells are less well explored. Here, we investigated the signals driving Toll-like receptor (TLR) ligand activation of type II NKT cells. We use the 24αβ mouse model expressing a transgenic Vα3.2 and Vβ9 type II NKT cell TCR on the C57/BL6 background. Using in vitro co-culture experiments with 24αβ type II NKT cells and FLT3L derived bone marrow dendritic cells (BMDCs) and TLR ligands, we have analyzed the factors required for type II NKT cell activation, applying BMDCs from different knock out mice. TLR stimulated DCs potently activated type II NKT cells to secrete IFN-γ in a CD1d and type I IFN independent manner. In contrast, an absolute requirement of IL12p40 and partial dependence on CD40, IL15 and IL18 for optimal IFN-γ induction was observed. Thus, our data suggest that TLR ligand - BMDC mediated activation of type II NKT cells requires cell - cell contact that includes CD40 - CD40L ligation, IL15, IL18 and IL-12, but not CD1d - TCR interaction.