Embryo, MammalianClone CellsEmbryo, NonmammalianMolecular Sequence DataBase SequenceAmino Acid SequenceCloning, MolecularCell LineCell DifferentiationBlastocystGene Expression Regulation, DevelopmentalEmbryonic DevelopmentT-LymphocytesCells, CulturedCell DivisionRNA, MessengerCell AggregationGastrulaDNAVitellinsEmbryonic Stem CellsLymphocyte ActivationBlastomeresXenopus ProteinsDNA, ComplementaryReceptors, Antigen, T-Cell, alpha-betaTransfectionCell LineageChick EmbryoCaenorhabditis elegansMitosisEpitopesReceptors, Antigen, T-CellT-Lymphocytes, Helper-InducerTeratomaPhenotypeXenopusXenopus laevisCarcinoma, EmbryonalMutationOvumPolymerase Chain ReactionTranscription, GeneticCD4-Positive T-LymphocytesTeratocarcinomaCell CycleTranscription FactorsChimeraTumor Cells, CulturedGenes, T-Cell Receptor betaBlastulaOocytesSequence Homology, Amino AcidEmbryonal Carcinoma Stem CellsEndodermGene Expression