BackgroundInformation | HumanTCR/CD3isacomplexstructureonthelymphocytesurface.ItconsistsoftheTCRalphabetaorTCRgammadeltaheterodimerandtheassociatedCD3complex.TheCD3complexiscomposedofsixpolypeptideswithusuallyfourdifferenttransmembraneCD3chains,gamma,delta,epsilon.andzeta.Threedifferentdimers,gammaepsilon,deltaepsilon?,andzetazeta,constitutetheCD3complex.TheMWofCD3epsilonis20000(Campana,1987).CD3isfirstdetectableinearlythymocytesanditsappearanceprobablyrepresentsoneoftheearliestsignsofcommitmenttotheTcelllineage.Incorticalthymocytes,duringearlystagesofmaturation,theCD3antigenispredominantlypresentinthecellcytoplasm.Inmedullarythymocyles,theCD3antigenispredominantlydetectedonthecellsurface(Swerdlow,1988;Beverley,1981).ThemajorityofTcellneoplasmsalsoexpressesCD3,butitisabsentfromnon-T-celllymphoidmalignancies(McMichael,1987).Consistentwiththepatternofsynthesisoftheantigeninnormalthymocytes,theearliestsitedetectablewithinneoplasticcellsisthecellcytoplasm(Swerdlow,1988). |