Effect of cyclosporin A on interleukin-15-activated umbilical cord blood natural killer cell function

Interleukin (IL)-15-activated natural killer (NK) cells may provide a graft-versus-leukemia (GvL) effect post-umbilical cord blood (CB) transplantation. The effect of cyclosporin A (CsA), a calcineurin-inhibitor used for prophylaxis of graft-versus-host disease (GvHD), on IL-15-mediated activation, cytotoxic function and target-induced apoptosis of CB NK cells, was examined in comparison with adult peripheral blood (APB) NK cells.

CsA was added to anti-CD3+/-IL-15-stimulated CB and APB mononuclear cells (MNC) for a 5-day incubation. CD3- CD56+ NK cell recovery was determined by flow cytometric analysis. Magnetic bead-purified CB and APB NK cells were stimulated with IL-15 for 18 h under the influence of CsA. NK activation (CD69), K562 cytotoxicity and NK-K562 interactions (CD54, perforin and annexin-V expression 4 h following contact with K562 cells) were assessed by flow cytometry.

CsA decreased CD3- CD56+ NK cell recovery in anti-CD3-stimulated CB MNC 5-day cultures, an effect that could be counteracted by IL-15; comparable effects were observed with APB. Short-term (18-h) experiments revealed that CsA down-regulated K562 cytotoxicity of IL-15-activated (P=0.018) but not resting (P=0.268) purified CB NK cells. IL-15-induced CB NK CD69 expression showed increased CsA sensitivity over APB (P=0.012). CsA down-regulated K562 cell-induced CD54 (P=0.028) but not perforin (P=0.416) expression of IL-15-activated CB NK cells. Target-induced apoptosis of IL-15-activated CB (P=0.043) but not APB (P=0.144) NK cells was decreased by CsA.

We have demonstrated differential CsA sensitivity of IL-15-activated CB and APB NK cells. These results may be used to improve the design of IL-15-activated NK cell adoptive immunotherapy in cancer patients receiving CsA post-CB transplantation.