Provided are methods for genetically engineering cells, including cells for use in connection with genetic engineering. In some embodiments, the provided methods including transduction of cells by incubation with a retroviral vector particle, e.g. lentiviral vector, in which, prior to the incubation, the cells have not been incubated with an activating or stimulating agent, such as have not been incubated with anti-CD3/anti-CD28 antibodies and/or one or more recombinant cytokines. In some embodiments, such methods result in features related to shortening or improving the process for genetically engineering cells. Also provided are resulting cells, transduced with a recombinant or heterologous gene, such as one encoding a chimeric receptor such as a chimeric antigen receptor, or other recombinant antigen receptor such as a transgenic T cell receptor, and compositions thereof. In some embodiments, the provided cells and compositions can be used in methods of adoptive immunotherapy.
