Elastase-AbELISAisasolidphaseenzymeimmunoassayemployingnativehumanElastaseforthequantitativeandqualitativedetectionofantibodiesagainstElastaseinhumanserum.Theassayisatoolinthediagnosisofautoimmunesystemicvasculitis.Elastaseisaserineproteasewithahomologyof54%toproteinase3,occuringmainlyinpolymorph-nuclearneutrophilicgranulocytes(PMN),inmacrophagesandendothelialcells.TheproteolyticactivityofElastasesecretedbyneutrophilsisresponsIBLeforthedismantlingofproteoglycans.FurThermore,Elastaseparticipatesdecisivelyintissuedestructionconnectedwithemphysemasandrheumatoidarthritis.AntibodiesagainstElastasebelongtothegroupofanti-neutrophilcytoplasmicantibodies(ANCA)whicharedirectedagainstcytoplasmiccomponentsofneutrophilicgranulocytesandmonocytes.ForthedetectionofANCAsindirectimmunofluorescencetestonethanol-fixedneutrophilshasbeentheestablishedmethodsofar.ItbecameapparentthatsomeANCAscreateacytoplasmicfluorescencepattern(thuscalledcANCA)whileotherscreateaperinuclearpattern(thepANCA).Asbothpatternsmaycovermultipleantigens,immunofluorescencedoesnotsufficeforasatisfyingdifferentialdiagnosisofvasculitis;thuseachIFTshouldbeverifiedwithspecificELISAtests.Proteinase3(PR3)andMyeloperoxidase(MPO)havebeenidentifiedasthemajorcANCAandpANCAantigens,respectively,butothercellularcomponentslikeLactoferrin,CathepsinGandElastasecauseperinuclearstaining,tooandthereforeareincludedintothegroupofpANCAs.DetectionofANCAsisausefullaboratorydiagnostictestforcertainsmallvesselvasculitidesandsomenon-vasculiticclinicalsyndromes,suchasinflammatoryboweldisease(IBD).AntibodiesagainstMPOcorrelatewithidiopathicorvasculitisassociatednecrotizingcrescenticglomerulonephritis.Theyarefoundfrequentlyin70%ofpatientswithmicroscopicpolyangiitisaswellas5-50%ofpatientswithChurg-Strausssyndrome.AutoantibodiestoPR3areaspecificSEROlogicalMarkerforWegener`sgranulomatosis(WG).AutoantibodiesagainstElastasearegenerallyassociatedwithinflammatoryrheumaticdisorders,e.g.rheumatoidarthritisandvasculitis.