• I Martínez, L Fernández, J Valentín, C Castillo, C Chamorro, and A Pérez-Martínez.
• Hospital Montepríncipe, Madrid, España.
• Med Intensiva. 2015 May 1; 39 (4): 213-21.

AimTo determine the role of natural killer (NK) cytotoxic activity in patients with suspected hemophagocytic lymphohistiocytosis syndrome (HLH).DesignA prospective study was conducted from September 2008 to February 2014.ScopeThe study was carried out in the Hematological Oncology Laboratory of Hospital Infantil Universitario Niño Jesús, Madrid (Spain).PatientsWe analyzed 30 peripheral blood samples from intensive care patients with suspected HLH. There were 18 males and 12 females, with a mean age of 4.7 years (range 0.2-22). NK cell cytotoxicity was compared with healthy controls according to age and sex.InterventionIn vitro NK cell cytotoxicity against the K562 cell line was determined by time-resolved fluorescence (Europium-TDA) under resting conditions, after interleukin 15 stimulation, and following block with Fas ligand antibody.Variable Of InterestNK cell cytotoxicity.ResultsA total of 20 patients showed a significant decrease of NK cell activity compared with controls (P=.001). Nine of these patients were diagnosed with primary HLH. A total of 10 patients were diagnosed with secondary HLH. Cytotoxic activity was normal in 10 subjects. None of them were diagnosed with HLH. Interleukin 15 stimulation increased NK cell cytotoxicity in secondary HLH, and blocking Fas ligand on NK cells decreased cytotoxic activity in primary HLH patients (P=.001).ConclusionsIn our experience, NK cell cytotoxic activity measured by time-resolved fluorescence is a simple and useful clinical diagnostic test for HLH. Interleukin 15 stimulation and Fas ligand blocking on NK cells could help differentiate between primary and secondary HLH.Copyright © 2014 Elsevier España, S.L.U. and SEMICYUC. All rights reserved.

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