The present invention relates to methods for developing engineered immune cells such as T-cells for immunotherapy that have a higher potential of persistence and/or engraftment in host organism. IN particular, this method involves an inactivation of at least one gene involved in self/non self recognition, combined with a step of contact with at least one non-endogenous immunosuppressive polypeptide. The invention allows the possibility for a standard and affordable adoptive immunotherapy, whereby the risk of GvH is reduced.