Increase of Ki-67+ natural killer cells in multiple sclerosis patients treated with interferon-β and interferon-β combined with low-dose oral steroids Lara Sanvito a, b, ⁎, Atsuko Tomita b , Norio Chihara b , Tomoko Okamoto c , Youwei Lin c , Masafumi Ogawa c , Bruno Gran a , Toshimasa Aranami b , Takashi Yamamura b a Division of Clinical Neurology, University of Nottingham, Nottingham, United Kingdom b Department of Immunology, National Institute of Neuroscience, Kodaira, Tokyo, Japan c Department of Neurology, National Center of Neurology and Psychiatry, Kodaira, Tokyo, Japan abstract article info Article history: Received 30 October 2010 Received in revised form 26 April 2011 Accepted 11 May 2011 Keywords: Natural killer cells Multiple sclerosis Interferon-β Prednisolone Corticosteroids Interferon-β (IFN-β) is known to expand regulatory CD56 bright natural killer (NK) cells in multiple sclerosis (MS). In this cross-sectional study we show that MS patients treated with IFN-β alone or in combination with low-dose prednisolone displayed increased proportion of all NK cell subsets in the active phase of the cell cycle (Ki-67 + ). There was no difference in NK cell apoptosis markers. In vitro experiments showed that both IFN-β and IFN-β in combination with corticosteroids increased the proportion of Ki-67 + NK cells. This study, although limited, shows that treatment with IFN-β affects NK cell cycle without altering NK cell apoptosis in MS patients. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Interferon-β (IFN-β) has been used as mainstream treatment in multiple sclerosis (MS) for decades. Early treatment with IFN-β reduces relapse rate and disability (Goodin et al., 2002). High dose short-term intravenous steroids are commonly used to accelerate recovery from acute relapses; however, there is not enough evidence to support a protective effect on long-term disability (Ciccone et al., 2008; Myhr and Mellgren, 2009). Of note, high dose pulses of IVMP had prolonged benefit on gadolinium enhancing lesions in IFN-β treated patients as compared to patients not on treatment with IFN-β (Gasperini et al., 1998). In recent studies pulsed oral methylprednis- olone (MP) as add-on therapy to subcutaneous IFN-β1a reduced relapse rate (Sorensen et al., 2009) but was not associated with reduction in long-term disability (Ravnborg et al., 2010). Combination treatment of intramuscular IFN-β1a and intravenous MP (IVMP) did not show significant benefit in relapsing-remitting MS (Cohen et al., 2009). Low-dose oral prednisolone (PDN) as add-on treatment to IFN-β is less commonly used in MS but is considered in clinical practice for patients with reduced response to IFN-β in some countries, including Japan. In a recent study IFN-β1a with either azathioprine or azathioprine with PDN in IFN-β naïve patients was not superior to monotherapy (Havrdova et al., 2009). Natural killer (NK) cell numbers and function are thought to be altered in MS (Benczur et al., 1980; Kastrukoff et al., 2003; De Jager et al., 2008). NK cells comprise two distinct populations, CD56 dim with predominant cytotoxic activity and CD56 bright with predominant cytokine producing and possibly immunoregulatory activity (Caligiuri, 2008). To date, there are still contradicting views on the role of NK cells in the pathogenic process underlying MS (Lunemann and Munz, 2008). Reports of reduction of NK cell numbers and function in MS patients and evidence from experimental autoimmune encephalomyelitis (EAE) suggest a protective role of this population (Zhang et al., 1997; Kastrukoff et al., 2003; De Jager et al., 2008). However, this subset can also exert a detrimental role in the inflammatory process within the CNS (Winkler-Pickett et al., 2008). Interestingly, recent work in EAE suggests an organ-specific suppressive function of NK cells towards Th17 cells which are considered by someone to be the main mediators of the inflammatory process in both EAE and MS (Hao et al., 2010). IFN-β is a type I interferon that can have opposite functional effects on different types of immune cells (Feng et al., 2002). The effects of IFN-β treatment on the adaptive and innate immune response in MS have been thoroughly investigated (Dhib-Jalbut and Marks, 2010). Treatment with IFN-β leads to a reduction of circulating total NK cells (Perini et al., 2000; Hartrich et al., 2003) and the expansion of CD56 bright NK cells, suggesting a protective role of this subpopulation (Saraste et al., 2007; Vandenbark et al., 2009). The mechanisms underlying the effects of IFN-β on both total and CD56 bright NK cells Journal of Neuroimmunology 236 (2011) 111–117 ⁎ Corresponding author at: Division of Clinical Neurology, University of Nottingham, C Floor, South Block, Queen's Medical Centre, Nottingham NG7 2UH, United Kingdom. Tel.: +44 115 849 3363; fax: +44 115 970 9738. E-mail address: lara.sanvito@gmail.com (L. Sanvito). 0165-5728/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jneuroim.2011.05.005 Contents lists available at ScienceDirect Journal of Neuroimmunology journal homepage: www.elsevier.com/locate/jneuroim