The present invention relates to a method for irradiating a population of mammalian cells comprising at least one target mammalian cell with electron beams and/or X-rays, characterized in that: (i) a composition comprising a population of mammalian cells is irradiated in vitro with electron beams and/or X-rays, the population of mammalian cells containing at least one target mammalian cell and the dose rate being within the range from 5 Gy/sec to 107 Gy/sec, and (ii) optionally viable target mammalian cells are isolated or enriched from the population of mammalian cells, and to agents obtainable thereby and to uses thereof.
