Potent expansion of human natural killer T cells using α-galactosylceramide (KRN7000)-loaded monocyte-derived dendritic cells, cultured in the presence of IL-7 and IL-15

Natural killer T (NKT) cells have an extremely restricted T-cell receptor repertoire, in man consisting of a Vα24 chain preferentially paired with a Vβ11 chain, and play crucial roles in various immune responses. Characterization of circulating Vα24⁺Vβ11⁺-T cells is hampered by their low frequencies. The α-galactosylceramide KRN7000 was reported to be presented by CD1d to NKT cells. Since dendritic cells (DC) are potent antigen presenting cells, and have been shown to express CD1d, we analyzed whether these cells could efficiently mediate expansion of Vα24⁺Vβ11⁺-T cells. During a 7-day co-culture of peripheral blood mononuclear cells and KRN7000-loaded mature monocyte derived DC (moDC) in the presence of interleukin-7 (IL-7) and IL-15, we observed up to 76-fold expansion of Vα24⁺Vβ11⁺-T cells. The expanded Vα24⁺Vβ11⁺-T cells expressed the cytotoxic molecule granzyme B, showed negligible expression of Fas ligand and could be induced to express high levels of interferon-γ, while retaining the capacity to produce IL-4. B cells, expressing CD1d, could also present KRN7000, but Vα24⁺Vβ11⁺-T cell expansion was only observed in the presence of IL-7 and/or IL-15. Considering the low frequency of circulating Vα24⁺Vβ11⁺-T cells, the present method for expansion of Vα24⁺Vβ11⁺-T cells using KRN7000-loaded mature moDC will be of value for the further characterization of this unique T cell subset.