Molecular Immunology 47 (2009) 28–36 Contents lists available at ScienceDirect Molecular Immunology journal homepage: www.elsevier.com/locate/molimm Regulatory T cells and ST2 signaling control diabetes induction with multiple low doses of streptozotocin Nemanja Zdravkovic a , Allen Shahin b , Nebojsa Arsenijevic a , Miodrag L. Lukic a,b,∗ , Eric P.K. Mensah-Brown c,∗∗ a Center for Molecular Medicine, Faculty of Medicine, University of Kragujevac, Kragujevac, Serbia b Department of Microbiology and Immunology, Faculty of Medicine and Health Sciences, UAE University, Al Ain, United Arab Emirates c Department of Anatomy, Faculty of Medicine and Health Sciences, UAE University, Al Ain, United Arab Emirates article info Article history: Received 16 December 2008 Accepted 21 December 2008 Available online 7 April 2009 Keywords: Autoimmunity CD25 Foxp3 IFN- IL-17 abstract Several peripheral mechanisms appear to be operational in limiting autoimmune damage of the islets of Langerhans and organ-specific T cell-mediated autoimmunity in general. These include cyclophos- phamide sensitive T regulatory cells (Treg cells) and Th2 derived cytokine downregulation. We used the model of multiple low doses of streptozotocin (MLD-STZ) induced diabetes in susceptible C57BL/6 mice and resistant BALB/c mice to study these regulatory mechanisms. We show that low dose cyclophos- phamide (CY) sensitive CD4 + CD25 + FoxP3 + Treg cell-dependent mechanisms can be demonstrated in C57Bl/6 mice susceptible to MLD-STZ diabetes induction. CY pretreatment decreased Foxp3 + cell count, glycemia, glycosuria and insulitis. In contrast, CY did not overcome resistance to diabetes induction in BALB/c mice. However, in BALB/c mice, deletion of ST2, an orphan member of the IL-1R family responsi- ble for Th2 cell signaling leads to enhanced susceptibility to diabetes induction as evaluated by level of glycemia and glycosuria, number of infiltrating cells and  cell loss. RT-PCR analysis of mRNA transcripts of diabetogenic cytokines revealed that the expression of TNF-, and IFN- was significantly enhanced in pancreatic lymph nodes by day 10 after diabetes induction in ST2-deficient mice in comparison with wild type BALB/c mice while IL-17 was detected only in ST2 -/- mice by day 21. Our results are compatible with the notion that Treg cells are involved in MLD-STZ diabetes in susceptible mice and demonstrate that ST2-mediated signaling may also be involved in limiting Th1/Th17-mediated autoimmune pathology in diabetes resistant strain. © 2009 Elsevier Ltd. All rights reserved. 1. Introduction For several years, the development of autoimmune chronic inflammatory diseases has been attributed to the activity of autore- active CD4 + T helper cells. T helper cells have until recently, been grouped into Th1 cells which produce interferon- (Mosmann et al., 1986; Abbas et al., 1996; McInnes and Schett, 2007) and Th2 cells which are characterized by IL-4, IL-5, IL-10 and IL-13 production (review in Lafaille, 1998). While the former has been implicated in multiple sclerosis, rheumatoid arthritis and type 1 diabetes (T1D) and their experimental models in mice and rats, the latter has generally been considered to be protective in these conditions (Fiorentino et al., 1989; Ria et al., 1998; Weiss et al., 2002). Only recently, another CD4 + T helper cell subset has been recognized as ∗ Corresponding author at: Department of Microbiology and Immunology, Faculty of Medicine and Health Sciences, UAE University, Al Ain, UAE. ∗∗ Corresponding author. E-mail address: ericb@uaeu.ac.ae (E.P.K. Mensah-Brown). an independent T cell lineage distinct from Th1 and Th2 cells. This Th17 subset of cells develops from naïve T cells under the com- bined influence of IL-6 and TGF- (Veldhoen et al., 2006; Bettelli et al., 2006; Mangan et al., 2006), and the transcription factors, RORt(Ivanov et al., 2006) and STAT3 (Yang et al., 2007; Laurence et al., 2007). IL-17, the product of Th17 cells has been shown to be important in the induction of organ-specific autoimmune diseases (Bettelli et al., 2007; Weaver et al., 2007). It has been demonstrated that a member of the IL-12 family cytokines, IL-23 promotes pro- liferation of IL-17-producing cells in the pool of activated memory cells (Aggarwal et al., 2003; Langrish et al., 2005) and is impor- tant for maintaining the Th17 phenotype (Veldhoen et al., 2006). Additionally, it has been argued that IFN- is inhibitory to IL-17 in experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (Cua et al., 2003). On the other hand, studies have also shown that autoimmunity can be mediated by dis- tinct effector populations producing both IL-17 and IFN- (Kroenke et al., 2008). Finally, it has been demonstrated in an adoptive trans- fer model that an early influx of Th1 cells is indispensable for the development of EAE while Th17 cells only enhance the pathology 0161-5890/$ – see front matter © 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.molimm.2008.12.023