title: The immunosuppressive effect of Wharton's jelly stromal cells depends on the timing of their licensing and on lymphocyte activation.
abstract: BACKGROUND
  Mesenchymal stromal cells (MSC) have been proven to have potent immunosuppressive action and hence have been proposed for the treatment of severe Graft Versus Host Disease. However, in most models, MSC were added at the same time of lymphocyte stimulation, which is quite different from what occurs in vivo.
  
  
  OBJECTIVE
  To investigate how the timing of lymphocyte activation and the exposure to activation-related cytokines (licensing) can influence the immunosuppressive action of Wharton's jelly stromal cells (WJSC).
  
  
  METHODS
  WJSC, licensed or not with activation-related cytokines, were added lymphocytes the same time or 24 hours after their stimulation with phytohaemoagglutinin. Proliferation of lymphocytes and cytokines production was measured after three days co-culture.
  
  
  RESULTS
  Lymphocytes stimulated in the presence of WJSC displayed a dramatic decrease in proliferation and production of cytokines, in spite of normal expression of activation markers. The suppression was weakened when targeted lymphocytes were seperated by a membrane and partially rescued by the addition of exogenous l-tryptophan, suggesting a major role for indoleamine 2,3-dioxigenase with a probable paracrine effect. Licensing of WJSC increased the immunosuppressive effect, in both contact and non-contact settings. The timing of WJSC licensing was crucial for the immunosuppressive action. Lymphocytes pre-stimulated alone for 24 h, and added afterwards to non-licensed WJSC, showed normal or even increased proliferation. On the other hand, their proliferation was strongly inhibited by licensed WJSC.
  
  
  CONCLUSIONS
  WJSC have a potent immunosuppressive function best realized with direct contact, and increased by licensing signals before and during lymphocyte stimulation. Our results could contribute to the set up of new WJSC-based therapies for severe autoimmuno disorders.
authors.affiliation: Institute for Maternal and Child Health IRCCS Burlo Garofolo and University of Trieste, Laboratories of Immunopathology, 34137 Trieste, Italy. erica.valencic@gmail.com
authors.forename: Erica
authors.initials: E
authors.lastname: Valencic
authors.forename: Elisa
authors.initials: E
authors.lastname: Piscianz
authors.forename: Marino
authors.initials: M
authors.lastname: Andolina
authors.forename: Alessandro
authors.initials: A
authors.lastname: Ventura
authors.forename: Alberto
authors.initials: A
authors.lastname: Tommasini
mesh_terms: D002452:Cell Count; D049109:Cell Proliferation / Q000187:drug effects; D016207:Cytokines / Q000096:biosynthesis / Q000378:metabolism*; D006801:Humans; D007108:Immune Tolerance / Q000187:drug effects / Q000276:immunology*; D007371:Interferon-gamma / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects / Q000276:immunology*; D008648:Mesoderm / Q000166:cytology*; D010835:Phytohemagglutinins / Q000494:pharmacology; D017154:Stromal Cells / Q000166:cytology / Q000187:drug effects / Q000276:immunology*; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors; D014364:Tryptophan / Q000494:pharmacology; D014470:Umbilical Cord / Q000166:cytology*
chemical_list: D016207:Cytokines; D010835:Phytohemagglutinins; D007371:Interferon-gamma; D014364:Tryptophan