The present invention is directed to a method for providing a cell comprising a chimeric antigen receptor (CAR) specific for one or more target antigens exposed on tumor cells characterized by providing a cell sample comprising tumor and non-tumor cells and repeating the steps of- contacting the cell tissue with a conjugate comprising a fluorescent moiety and an antigen recognizing moiety- removing unbound conjugate from the cell tissue and detecting cells bound to the conjugate by the fluorescence radiation emitted by the fluorescent moieties of the first conjugates- erasing the fluorescence emitted by the fluorescent moieties of the conjugates with conjugates comprising a fluorescent moiety and antigen recognizing moieties recognizing different antigensuntil identifying at least two conjugates provided with antigen recognizing moieties recognizing different antigens, allowing in combination to discriminate between tumor cells and non-tumor cells andproviding cells with the identified at least two antigen recognizing moieties as chimeric antigen receptor (CAR).
