Method for obtaining a preparation enriched in engineered T cells with exogenous immune receptors, comprising the steps of: a) providing a mixture of T cells comprising - engineered T cells with exogenous immune receptors comprising a murinized constant region, wherein expression of endogenous alpha beta T cell receptors is suppressed; and - non-engineered T cells with endogenous alpha beta T cell receptors, wherein step a) comprises the steps of: i. providing T cells; ii. providing a nucleic acid or nucleic acids encoding an exogenous immune receptor; iii. introducing the nucleic acid or nucleic acids into the T cells to thereby provide a mixture of T cells comprising engineered T cells with exogenous immune receptors and non-engineered T cells with endogenous alpha beta T cell receptors; b) contacting the mixture of T cells with an antibody that specifically binds to the endogenous alpha beta T cell receptor, to allow formation of an antibody-non-engineered T cell complex; c) removing the antibody-non-engineered T cell complex from the mixture of T cells to thereby obtain a preparation enriched in engineered T cells with exogenous immune receptors. a) providing a mixture of T cells comprising - engineered T cells with exogenous immune receptors comprising a murinized constant region, wherein expression of endogenous alpha beta T cell receptors is suppressed; and - non-engineered T cells with endogenous alpha beta T cell receptors, wherein step a) comprises the steps of: i. providing T cells; ii. providing a nucleic acid or nucleic acids encoding an exogenous immune receptor; iii. introducing the nucleic acid or nucleic acids into the T cells to thereby provide a mixture of T cells comprising engineered T cells with exogenous immune receptors and non-engineered T cells with endogenous alpha beta T cell receptors; - engineered T cells with exogenous immune receptors comprising a murinized constant region, wherein expression of endogenous alpha beta T cell receptors is suppressed; and - non-engineered T cells with endogenous alpha beta T cell receptors, wherein step a) comprises the steps of: i. providing T cells; ii. providing a nucleic acid or nucleic acids encoding an exogenous immune receptor; iii. introducing the nucleic acid or nucleic acids into the T cells to thereby provide a mixture of T cells comprising engineered T cells with exogenous immune receptors and non-engineered T cells with endogenous alpha beta T cell receptors; i. providing T cells; ii. providing a nucleic acid or nucleic acids encoding an exogenous immune receptor; iii. introducing the nucleic acid or nucleic acids into the T cells to thereby provide a mixture of T cells comprising engineered T cells with exogenous immune receptors and non-engineered T cells with endogenous alpha beta T cell receptors; b) contacting the mixture of T cells with an antibody that specifically binds to the endogenous alpha beta T cell receptor, to allow formation of an antibody-non-engineered T cell complex; c) removing the antibody-non-engineered T cell complex from the mixture of T cells to thereby obtain a preparation enriched in engineered T cells with exogenous immune receptors. <EOS>