I think you better than Endoxan (cyclophosphamide), which is still primarily used cytostatic real immunosuppressant, such as Cyclosporine or Tacrolimus in any case will give a better response simulation with SCID mouse!
This is a basic imusupresivna therapy and should be monitored its effect on the masses and compare mechanism and clinical picture with SCID mouse if its effects are too strong it should be in an experiment to reduce or add amplify with cyclophosphamide or azathioprine, of course provided that I understand fully your question!
Otherwise I think you get the idea for an experimental project basically very good compared artificial immune deficiency caused by immunosuppressants with severe combined immunodeficiency SCID mice with and gives a lot of opportunities to improve .I folow very happy project and try to help as much as I can and know ... of course !