Differential expansion of umbilical cord blood mononuclear cell-derived natural killer cells dependent on the dose of interleukin-15 with Flt3L.
OBJECTIVE
We investigated the effect of interleukin-15 (IL-15) with Flt3 ligand (Flt3L) on the expansion and activation of NK cells derived from umbilical cord blood mononuclear cells (UCB-MNCs).


METHODS
UCB-MNCs were cultured at 1 to 100 ng/mL of IL-15 + Flt3L (10 ng/mL) compared with 1 to 500 ng/mL of IL-2 + Flt3L (10 ng/mL). Cultured cells were assessed for surface marker and we calculated absolute number of NK cells and T cells. The cytotoxic activity was analyzed with purified NK cells.


RESULTS
After 2 weeks culture with 5 ng/mL of IL-15 + Flt3L, the fold inductions of absolute number of NK cells significantly increased to 20.9-fold +/- 9.3-fold of the number of NK cells on day 0 (p < 0.05), with 24.4-fold +/- 16.1-fold of T cells. But with 50 ng/mL of IL-15 + Flt3L, fold induction of NK cells decreased to 5.1-fold +/- 3.9-fold, while T cells showed 34.8-fold +/- 18.7-fold (n = 8). The proportion of NK vs T cells showed to be significantly higher (1.61 +/- 0.91) with 5 ng/mL of IL-15 than with 50 ng/mL of IL-15 (0.12 +/- 0.03). Such proportional change of NK/T cells could not be observed with IL-2. Immunophenotypes of CD56, CD16, LFA1, CD94, CD8, and perforin of cultured NK cells with 10 ng/mL of IL-15 + Flt3L showed the same pattern of those with 50 ng/mL of IL-2 + Flt3L. Cytotoxic activity against K562 of cultured NK cells resulted in the same level as adult peripheral blood (PB)-derived NK cells.


CONCLUSIONS
Higher induction of NK cells derived from UCB-MNCs was achieved by low dose (5 to 10 ng/mL) rather than high dose (> 50 ng/mL) of IL-15.
Nagamura-Inoue
Tokiko
T
Division of Cell Processing, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan.
Mori
Yuka
Y
Yizhou
Zheng
Z
Watanabe
Nobukazu
N
Takahashi
Tsuneo A
TA
D019002:CD56 Antigen / Q000032:analysis; D002478:Cells, Cultured; D003602:Cytotoxicity, Immunologic; D005312:Fetal Blood / Q000166:cytology*; D006801:Humans; D016130:Immunophenotyping; D019409:Interleukin-15 / Q000494:pharmacology*; D007376:Interleukin-2 / Q000494:pharmacology; D007694:Killer Cells, Natural / Q000166:cytology / Q000187:drug effects* / Q000276:immunology; D007963:Leukocytes, Mononuclear / Q000166:cytology / Q000187:drug effects*; D008565:Membrane Proteins / Q000494:pharmacology*
D019002:CD56 Antigen; D019409:Interleukin-15; D007376:Interleukin-2; D008565:Membrane Proteins; C084881:flt3 ligand protein