title: TIM-1 defines a human regulatory B cell population that is altered in frequency and function in systemic sclerosis patients.
abstract: BACKGROUND
  Systemic sclerosis (SSc) is a systemic autoimmune disease characterized by excessive production of extracellular matrix by fibroblasts on skin and internal organs. Although Th2 cells have been involved in fibroblast stimulation, hyperactivated B cells may also play an important role. Regulatory B cells (Bregs) are cells capable of inhibiting inflammatory responses and controlling autoimmune diseases. Although many Breg populations have in common the ability to produce high amounts of IL-10, a unique surface marker defining most human Bregs is lacking. It has been described in mice that T cell Ig and mucin domain protein 1 (TIM-1) is an inclusive marker for Bregs, and that TIM-1+ B cells are able to prevent the development of autoimmunity. The aim of this work was to evaluate TIM-1 as a marker for human IL-10+Bregs, and to determine whether TIM-1+ B cells are defective in SSc patients.
  
  
  METHODS
  SSc patients (n = 39) and 53 healthy subjects were recruited. TIM-1 and IL-10 expression was assessed in resting or activated peripheral blood CD19+B cells by flow cytometry. The regulatory function of TIM-1+or activated B cells from SSc patients and healthy subjects was assessed in autologous and allogenic co-cultures with CD4+T cells, where T cell proliferation and IFN-γ, IL-17, TNF-α and IL-4 production by T cells was measured by flow cytometry.
  
  
  RESULTS
  TIM-1 and IL-10 were preferentially expressed in transitional B cells, but were upregulated in naïve and memory B cells upon stimulation. The frequency of transitional TIM-1+IL-10+B cells was significantly decreased in SSc patients compared to healthy controls. In addition, activated B cells from SSc patients induced stronger allogenic Th1 and Th2 responses than activated B cells from healthy controls. Finally, TIM-1+B cells, including transitional and non-transitional cells, exhibited a higher CD4+T cell suppressive ability than TIM-1-B cells in healthy controls, but not in SSc patients.
  
  
  CONCLUSIONS
  TIM-1 is a unique marker for the identification of a human IL-10+Breg subpopulation which is partially superimposed with transitional B cells. Alterations in TIM-1+B cells could contribute to the development of autoimmune diseases such as SSc.
authors.affiliation: Programa Disciplinario de Inmunología, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, and Millennium Institute in Immunology and Immunotherapy, Santiago, Chile.
authors.forename: Octavio
authors.initials: O
authors.lastname: Aravena
authors.affiliation: Programa Disciplinario de Inmunología, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, and Millennium Institute in Immunology and Immunotherapy, Santiago, Chile.
authors.forename: Ashley
authors.initials: A
authors.lastname: Ferrier
authors.affiliation: Centre for Rheumatology Research, Department of Medicine, University College London, London, UK.
authors.forename: Madhvi
authors.initials: M
authors.lastname: Menon
authors.affiliation: Centre for Rheumatology Research, Department of Medicine, University College London, London, UK.
authors.forename: Claudia
authors.initials: C
authors.lastname: Mauri
authors.affiliation: Programa Disciplinario de Inmunología, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, and Millennium Institute in Immunology and Immunotherapy, Santiago, Chile.
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Aguillón
authors.affiliation: Programa Disciplinario de Inmunología, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, and Millennium Institute in Immunology and Immunotherapy, Santiago, Chile.|Departamento de Medicina, Hospital Clínico, Universidad de Chile, Santiago, Chile.
authors.forename: Lilian
authors.initials: L
authors.lastname: Soto
authors.affiliation: Programa Disciplinario de Inmunología, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, and Millennium Institute in Immunology and Immunotherapy, Santiago, Chile. dfcatalan@med.uchile.cl.
authors.forename: Diego
authors.identifier: http://orcid.org/0000-0002-4353-1229
authors.initials: D
authors.lastname: Catalán
mesh_terms: D000328:Adult; D016175:B-Lymphocyte Subsets / Q000276:immunology*; D060151:B-Lymphocytes, Regulatory / Q000276:immunology*; D015415:Biomarkers / Q000032:analysis; D002469:Cell Separation; D018920:Coculture Techniques; D005260:Female; D005434:Flow Cytometry; D000072596:Hepatitis A Virus Cellular Receptor 1 / Q000032:analysis / Q000096:biosynthesis* / Q000276:immunology; D006801:Humans; D016753:Interleukin-10 / Q000276:immunology; D008213:Lymphocyte Activation / Q000276:immunology; D008297:Male; D008875:Middle Aged; D012595:Scleroderma, Systemic / Q000276:immunology*
chemical_list: D015415:Biomarkers; C491143:HAVCR1 protein, human; D000072596:Hepatitis A Virus Cellular Receptor 1; C508609:IL10 protein, human; D016753:Interleukin-10
keywords: IL-10; Regulatory B cells; Systemic sclerosis; TIM-1