In some aspects, isolated transgenic cells (e.g., transgenic T cells) are provided that comprise or express a transgene and DHFRFS and/or TYMSSS. Methods for selecting transgenic cells are also provided.Dans certains aspects, linvention concerne des cellules transgéniques isolées (par exemple, lymphocytes T transgéniques) qui comprennent ou expriment un transgène et DHFRFS et/ou TYMSSS. Linvention concerne également des procédés de sélection de cellules transgéniques.