¹The Basel Stem Cell Transplant Team, Basel University Hospitals, Switzerland

Correspondence: Professor A Tichelli, Internal Medicine, Hematology Division, Basel University Hospitals, Petersgraben 4, Basel CH-4031, Switzerland. Fax: +41 61 265 44 50; E-mail: tichelli@datacomm.ch

²Both authors contributed equally to this work

Received 21 March 2004; Accepted 11 June 2004; Published online 30 September 2004.

Abstract

This pilot study tested feasibility of natural killer cell purification and infusion (NK-DLI) in patients after haploidentical hematopoietic stem cell transplantation (HSCT). The aim was to obtain 1.0 10⁷/kg CD56+/CD3- NK cells and <1.0 10⁵/kg CD3+ T cells. Mononuclear cells were collected by 10 l leukapheresis. A two-step ex vivo procedure was used to purify NK cells, using an immunomagnetic T-cell depletion, followed by NK-cell enrichment. Five patients with high-risk myeloid malignancies were included, presenting 3–12 months after a haploidentical HSCT with mixed chimerism (3), impending graft failure (1) or early relapse (1). The purified product contained a median of 1.61 10⁷/kg (range 0.21–2.2) NK cells and 0.29 10⁵/kg (0.11–1.1) T cells. A purity of NK cells of 97% (78–99), a recovery of 35.5% (13–75), and a T-cell depletion of 3.55 log (2.9–4.5) was achieved. Infusions were well tolerated and none of the patients developed graft-versus-host disease. We observed an increase in donor chimerism in 2/5, stable mixed chimerism, decreasing chimerism and relapse of AML in one patient each. Selection of NK-DLI is technically feasible. NK cells are well tolerated when used as adoptive immunotherapy in recipients of haploidentical HSCT.