Investigations on cell lineage and tissue interactions in the developing bursa of Fabricius through interspecific chimeras☆

[摘要] EmbryonicrudimentsofthebursaofFabriciusweregraftedbetweenquailandchickembryosatvariousdevelopmentalstages.Thedistinctmorphologicaldifferencesbetweenthenucleiofthequailandthoseofthechickwereusedtodeterminetheoriginofcellsindifferentiatedtissueatvarioustimeslongaftertheinitialgraft.ItwasthuspossibletodemonstratethatthelymphocyteswhichdevelopinthebursaofFabriciusdonotoriginatefromtheepitheliumorfromthemesenchymeoftherudimentbutarisefromprecursorcellswhichreachtheorganviathecirculation.Theinflowofhemopoieticstemcellstakesplacebetween7and11daysofincubationinthequailembryo.Inthechicktheinfluxbeginsduringthe8thdayofincubationandextendsuntilatleastthe15thday.Thebasophiliccellswhichappearintherudimentduringbursalontogenywereshowntobehemopoieticprecursorcellsofextrinsicorigin.Intheearlystagesofbursaldevelopmentthebasophiliccellsseemtostayinthemesenchymalportionoftheorganforawhilebeforeinvadingtheepithelium.Someofthemremaininthemesenchymeandundergogranulocyticdifferentiation.Onlythecellswhichinvadetheepitheliumdevelopintolymphocytes.Bursalhistogenesiscanoccuronlywhenthetwoprimarycomponentsoftherudiment,i.e.,theepitheliumandthemesenchyme,areassociated.Themesenchymeofthebursapropercannotbereplacedbyanotherkindofmesenchymalsubstrateforpromotingthedevelopmentoftheepithelium.Whenassociatedwiththesomatopleuralmesoderm,thelattereitherremainsinanundifferentiatedstateorevendedifferentiates.

[学科分类] 生物科学（综合）