The present invention provides a transgenic mouse which comprises a deficiency for murine T lymphocytes, B lymphocytes and NK cells, a deficiency for murine MHC class I and MHC class II molecules, and a functional xenogenic SIRPα transgene. This mouse is useful for in vivo screening of various compounds, including immuno-therapeutic agents and vaccines. The said mouse is also useful for testing the in vivo metabolism of xenobiotic compounds.
