A method for engineering less alloreactive immune cells, including T-cells that express chimeric antigen receptors (CARs), using a nucleotide sequence in form of an RNA encoding a anti-TCR CAR to achieve the transient expression of anti- TCR CAR at the cellsurface. The transient expression of the anti-TCR CAR recognized by the alpha beta TCR on the cell surface unexpectedly enabled the a purification of the TCR-negative CAR expressing cells. The TCR-negative CAR expressing immune cells can be used in adoptive therapy to treat diseases associated with cell surface antigens, such as cancer with less side effects, in particular less GVHD.
