title: In human basophils, IL-3 selectively induces RANKL expression that is modulated by IgER-dependent and IgER-independent stimuli.
abstract: BACKGROUND
  Receptor activator of NF-κB ligand (RANKL) is expressed as either surface (hRANKL1, hRANKL2) or soluble (hRANKL3) form. RANKL is involved in multifaceted processes of immunoregulation and bone resorption such as they occur in rheumatoid arthritis (RA). Interestingly, activated basophils, which are effector cells in allergic inflammation, contribute to the progress of collagen-induced arthritis (CIA), a mouse model for RA. Here, we investigate under which conditions human basophils express RANKL.
  
  
  METHODS
  Among other stimuli, basophils were cultured with IL-3 alone. Alternatively, as a secondary stimulus, IgER-dependent or IgER-independent agents were added simultaneously either with IL-3 or after prolonged IL-3 culturing. Expression of RANKL protein and mRNA was analyzed by flow cytometry, ELISA, and real-time PCR. A coculture system was applied to investigate biological activity of basophil-derived RANKL.
  
  
  RESULTS
  We show that in human basophils, IL-3 but no other stimulus induces de novo expression of soluble and surface RANKL, of which the latter enhances survival of MoDC. Upon simultaneous stimulation, IgER cross-linking reduces surface RANKL expression, while IgER-independent stimuli have no effect. This is in contrast to consecutive stimulation, as triggering with both IgER-dependent and IgER-independent stimuli enhances RANKL expression, particularly in its soluble form. Real-time PCR analysis shows that RANKL expression is mainly regulated at the mRNA level.
  
  
  CONCLUSIONS
  This study identifies IL-3 as a potent inducer of RANKL expression in human basophils, suggesting them to interact with bone physiology and activation of immune cells. IgER-dependent and IgER-independent stimuli modulate the IL-3-mediated RANKL expression in a time- and stimulus-dependent fashion.
authors: Institute of Immunology, University Hospital Bern, Inselspital, Bern, Switzerland.
authors: C
authors: C
authors: Huber
authors: A
authors: A
authors: Odermatt
authors: B
authors: B
authors: Hagmann
authors: C A
authors: CA
authors: Dahinden
authors: M
authors: M
authors: Fux
mesh_terms: D001491:Basophils / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D016130:Immunophenotyping; D007377:Interleukin-3 / Q000378:metabolism* / Q000494:pharmacology; D053245:RANK Ligand / Q000235:genetics / Q000378:metabolism*; D017455:Receptors, IgE / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D007377:Interleukin-3; D053245:RANK Ligand; D017455:Receptors, IgE
keywords: C5a/fMLP; IL-3; anti-FcεRIα antibody; human basophils; receptor activator of NF-κB ligand