title: In vitro induction of functional allergen-specific CD4+ CD25high Treg cells in horses affected with insect bite hypersensitivity.
abstract: BACKGROUND
  Insect bite hypersensitivity (IBH) is a recurrent allergic dermatitis of horses with similarities to human atopic eczema, caused by bites of insects of the genus Culicoides. Previous studies suggested a dysregulated T cell tolerance to Culicoides allergen in IBH-affected horses.
  
  
  OBJECTIVE
  We have investigated whether the suppressive function of CD4(+) CD25(high) cells is impaired in IBH-affected horses and possible ways to restore it.
  
  
  METHODS
  CD4(+) CD25(-) cells sorted from peripheral blood mononuclear cells (PBMC) were stimulated with irradiated autologous PBMC pulsed with Culicoides or tetanus toxoid as control antigen, in the presence of CD4(+) CD25(high) cells. Furthermore, Culicoides-specific CD4(+) CD25(high) regulatory cells were expanded or induced from CD4(+) CD25(-) cells in vitro in the presence of a combination of rIL-2 and rTGF-β1 (rIL-2/rTGF-β1) or of retinoic acid and rapamycin (RetA/Rapa). Proliferation was determined by [(3) H] thymidine incorporation and cytokine production measured by flow cytometry.
  
  
  RESULTS
  The ability of Culicoides- but not tetanus-stimulated CD4(+) CD25(high) cells to suppress proliferation of CD4(+) CD25(-) cells was significantly lower in IBH-affected horses (28%) than in healthy controls (86%). The decreased suppression in IBH-affected horses was associated with a significantly higher proportion of IL-4(+) cells and a lower percentage of FoxP3(+) IL-10(+) compared to controls. Addition of rIL-2/rTGF-β1 or of RetA/Rapa to Culicoides-stimulated CD4(+) CD25(high) cells from IBH-affected horses significantly increased the proportion of FoxP3(+) IL-10(+) cells. We also found that RetA/Rapa induced a more significant decrease in the frequency of IL-4(+) cells than rIL-2/rTGF-β1. Moreover, the suppressive activity of Culicoides-stimulated CD4(+) CD25(high) cells was significantly restored by both rIL-2/rTGF-β1and RetA/Rapa, albeit in an antigen-unspecific manner. In contrast, in vitro induced Culicoides-specific CD4(+) CD25(high) cells suppressed proliferation of CD4(+) CD25(-) cells in an antigen-specific manner.
  
  
  CONCLUSIONS
  The in vitro induction of functional allergen-specific Treg cells in IBH-affected horses suggests a potential therapeutic use of these cells in allergy.
authors.affiliation: Department of Clinical Research and Veterinary Public Health, Vetsuisse Faculty, University of Bern, Bern, Switzerland. eman.hamza@vetsuisse.unibe.ch
authors.forename: E
authors.initials: E
authors.lastname: Hamza
authors.forename: C A
authors.initials: CA
authors.lastname: Akdis
authors.forename: B
authors.initials: B
authors.lastname: Wagner
authors.forename: F
authors.initials: F
authors.lastname: Steinbach
authors.forename: E
authors.initials: E
authors.lastname: Marti
mesh_terms: D000485:Allergens / Q000276:immunology*; D000818:Animals; D015704:CD4 Antigens / Q000378:metabolism; D016207:Cytokines / Q000096:biosynthesis; D018984:Epitopes, T-Lymphocyte / Q000276:immunology*; D005260:Female; D051858:Forkhead Transcription Factors / Q000096:biosynthesis; D006736:Horses / Q000276:immunology*; D006967:Hypersensitivity / Q000662:veterinary*; D007108:Immune Tolerance / Q000187:drug effects; D007299:Insect Bites and Stings / Q000276:immunology*; D007376:Interleukin-2 / Q000494:pharmacology; D053645:Interleukin-2 Receptor alpha Subunit / Q000378:metabolism; D008213:Lymphocyte Activation / Q000276:immunology; D008297:Male; D050378:T-Lymphocytes, Regulatory / Q000276:immunology* / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000494:pharmacology
chemical_list: D000485:Allergens; D015704:CD4 Antigens; D016207:Cytokines; D018984:Epitopes, T-Lymphocyte; D051858:Forkhead Transcription Factors; D007376:Interleukin-2; D053645:Interleukin-2 Receptor alpha Subunit; D016212:Transforming Growth Factor beta
keywords: CD4+ CD25+ T cells; FoxP3; IBH; IL-10; IL-4; Icelandic horses; Treg expansion; Treg induction; Treg suppression; allergy; rIL-2 and rTGF-β1.; retinoic acid and rapamycin