A Soluble Form of CTLA-4 Is Present in Paediatric Patients with Acute Lymphoblastic Leukaemia and + Correlates with CD1d Expression Rita Simone1,2, Claudya Tenca1, Franco Fais1, Matteo Luciani3, Giulio De Rossi3, Giampaola Pesce4, Marcello Bagnasco4, Daniele Saverino 1 * 1 Department of Experimental Medicine – Section of Human Anatomy, University of Genova, Genova, Italy, 2 The Feinstein Institute for Medical Research, North Shore-LIJ Health System, Manhasset, New York, United States of America, 3 Department of Pediatric Haematology and Oncology, Ospedale Bambino Gesu` , Rome, Italy, 4 Medical and Radiometabolic Therapy Unit, Department of Internal Medicine, University of Genova, Genova, Italy Abstract CTLA-4 is a key factor in regulating and maintaining self tolerance, providing a negative signal to the T cell and thus limiting immune responses. Several polymorphisms within the CTLA-4 gene have been associated with an increased risk of developing autoimmune diseases and, very recently, with susceptibility to human cancer. Acute lymphoblastic leukemia is a clonal disorder of lymphoid progenitors representing the most frequent malignancy of childhood. Here, we show the presence at significantly elevated levels of a circulating soluble form of CTLA-4 in 70% of B-ALL pediatric patients with active disease, the positive correlation between the percentage of leukemic B lymphocytes and the amount of serum sCTLA-4, and the expression of sCTLA-4 transcript by B cells in patients. Finally, a correlation between CD1d expression (a negative prognostic marker) and the sCTLA-4 in B-ALL patients was observed. This suggests a possible role of this soluble molecule as a marker of progression or severity of the neoplastic disease. Citation: Simone R, Tenca C, Fais F, Luciani M, De Rossi G, et al. (2012) A Soluble Form of CTLA-4 Is Present in Paediatric Patients with Acute Lymphoblastic Leukaemia and Correlates with CD1d+ Expression. PLoS ONE 7(9): e44654. doi:10.1371/journal.pone.0044654 Editor: Ann M. Moormann, University of Massachusetts Medical School, United States of America Received June 1, 2012; Accepted August 6, 2012; Published September 25, 2012 Copyright: 2012 Simone et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported by grants from Fondazione CARIGE and from Associazione ‘‘Davide Ciavattini’’ Onlus. Fondazione CARIGE as well as Associazione ‘‘Davide Ciavattini’’ Onlus had no involvement in study design, nor in the collection, analysis and interpretation of data, nor in the writing of the report and in the decision to submit the paper for publication. Competing Interests: The authors have declared that no competing interests exist. * E-mail: daniele.saverino@unige.it Introduction Acute lymphoblastic leukemia (ALL) is a clonal disorder of lymphoid progenitors with distinctive morphologic, immunophe- notypic and genotypic features and represents the most frequent malignancy of childhood [1]. ALL affects T- or B-lineage precursor cells, the latter accounting for approximately 80% of the cases in Europe and the USA. Immunophenotype allows further subdivision of B lineage ALL into pro-B (CD19+, CD102), common (CD19+, CD10+), pre-B (CD19+, cytoplasmic immuno- globulin (Ig)+) and mature B (surface Ig+). However, with some exceptions, this classification has little value for survival prediction [2]. Several prognostic factors that herald poor outcome have been described in childhood ALL [3,4]. Infants less than 1-year of age (infant leukemia) have a poor rate of survival [1]. Thus, beyond a better understanding of the molecular mechanisms of disease and resistance to chemotherapy, the identification of new markers, potentially able to be used to guide the development of new targeted chemotherapies or immunotherapeutic agents, which may be used to intensify therapy in children with ALL who have poorer. CD1d is a monomorphic molecule that provides a suitable target for immunotherapy in view of the characterization of a glycolipid, alwa-galactosylceramide (alwa-GalCer), capable of being presented to CD1d-restricted T cells with cytotoxic potential [5,6]. We have previously demonstrated the expression of CD1d on leukemic B-cells in a proportion of high risk pediatric ALL patients with poor prognosis [7]. Cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) is a homodimeric glycoprotein belonging to the human Ig gene superfamily originally described on the surface of murine and human activated T cells [8]. The vast majority of in vitro and in vivo studies on CTLA-4 support its negative role on T-cell activation contributing to the physiologic termination of the immune response [13,14] CTLA-4 inhibitory function occurs upon interaction with its ligands, CD80 (B7.1) and CD86 (B7.2), expressed on antigen-presenting cells (APCs), resulting in inhibi- tion of IL-2, IFN-camma, IL-4 cytokines production, IL-2 receptor expression and cell cycle progression [15,16]. Several mechanisms of CTLA-4 function have been proposed including ligand competition with the positive T-cell costimulatory CD28 molecule [17], interference of TCR signalling [18] and inhibition of cyclin D3 and cyclin-dependent kinases (cdk4/cdk6) production [19]. A possible function of CTLA-4 in the regulatory role of suppressor CD4+CD25+ T cells has generated widespread interest indicating another mechanism by which CTLA-4 might downregulate immune responses [20] and also promote peripheral tolerance [21]. Otherwise, growing evidence supports its wider role as an immune attenuator which may also act in other cell lineages, such PLOS ONE | www.plosone.org 1 September 2012 | Volume 7 | Issue 9 | e44654