Expansion of Valpha24(+)Vbeta11(+) NKT cells from cord blood mononuclear cells using IL-15, IL-7 and Flt3-L depends on monocytes.

Human Valpha24(+)Vbeta11(+) NKT cells are a unique T cell population specifically and potently activated by alpha-galactosylceramide (alphaGalCer; KRN7000) presented by CD1d. Here, we present a simple and efficient method for expanding Valpha24(+)Vbeta11(+) NKT cells from human cord blood mononuclear cells (CBMNC) using alphaGalCer in the presence of interleukin (IL)-15, IL-7 and Flt3-L. The addition of alphaGalCer from day 0, compared to its addition from day 8 or day 15, induced a greater expansion of NKT cells. The maximal expansion of NKT cells was observed after 15 days (2300-fold). Thereafter, the number of NKT cells decreased slowly, a decrease that was correlated with the diminution of CD1d-positive cells. NKT cell proliferation induced by alphaGalCer was not observed when CD1d-expressing monocytes were depleted from CBMNC, whereas B cell and dendritic cell depletions had no effect. Expanded NKT cells were CD4(+)CD8(-) and secreted both IL-4 and IFN-gamma. In this system, CD3(+) T cells and CD3(-)CD56(+) NK cells were also expanded. However, the expansion of NKT cells had no significant functional effect on T and NK cells. This expansion method of CBMNC-derived NKT cells is simple and may be helpful for clinical use.