title: IL-33 fine tunes mast cell degranulation and chemokine production at the single-cell level.
abstract: BACKGROUND
  Mast cells are versatile key components of allergy and inflammation known to respond to both innate and adaptive immunologic stimuli. However, the response of individual mast cells to cumulative stimuli remains poorly understood.
  
  
  OBJECTIVE
  We sought to dissect mast cell responses at the single-cell level and their potentiation by IL-33.
  
  
  METHODS
  We monitored mast cell degranulation in real time by exploiting the capacity of fluorochrome-labeled avidin to stain degranulating cells. During the degranulation process, the granule matrix is externalized and immediately bound by fluorochrome-labeled avidin present in the culture medium. The degranulation process is monitored by using either time-lapse microscopy or fluorescence-activated cell sorting analysis.
  
  
  RESULTS
  Single-cell analysis revealed a strong heterogeneity of individual mast cell degranulation responses. We observed that the number of degranulating mast cells was graded according to the FcεRI stimulation strength, whereas the magnitude of individual mast cell degranulation remained unchanged, suggesting an all-or-none response of mast cells after FcεRI triggering. IL-33 pretreatment increased not only the number of degranulating and chemokine-producing mast cells but also the magnitude of individual mast cell degranulation and chemokine production.
  
  
  CONCLUSIONS
  We illustrate the effect of IL-33 on mast cell biology at the single-cell level by showing that IL-33 potentiates IgE-mediated mast cell responses by both increasing the number of responding cells and enhancing the responses of individual mast cells.
authors.affiliation: INSERM U1043, and Université de Toulouse, UPS, Centre de Physiopathologie de Toulouse Purpan (CPTP), Toulouse, France.
authors.forename: Régis
authors.initials: R
authors.lastname: Joulia
authors.affiliation: INSERM U1043, and Université de Toulouse, UPS, Centre de Physiopathologie de Toulouse Purpan (CPTP), Toulouse, France.
authors.forename: Fatima-Ezzahra
authors.initials: FE
authors.lastname: L'Faqihi
authors.affiliation: INSERM U1043, and Université de Toulouse, UPS, Centre de Physiopathologie de Toulouse Purpan (CPTP), Toulouse, France.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Valitutti
authors.affiliation: INSERM U1043, and Université de Toulouse, UPS, Centre de Physiopathologie de Toulouse Purpan (CPTP), Toulouse, France. Electronic address: eric.espinosa@inserm.fr.
authors.forename: Eric
authors.initials: E
authors.lastname: Espinosa
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D015550:Cell Degranulation / Q000502:physiology*; D002478:Cells, Cultured; D018925:Chemokines / Q000378:metabolism*; D006801:Humans; D007073:Immunoglobulin E / Q000494:pharmacology; D008407:Mast Cells / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D010529:Peritoneal Cavity / Q000166:cytology
chemical_list: D018925:Chemokines; D007073:Immunoglobulin E; D002118:Calcium
keywords: IL-33; Mast cells; avidin; degranulation; time-lapse flow cytometry