The present invention relates to a method for the manufacture of an
antibody which specifically binds to an
antigen, preferably, being a
hapten such as
fentanyl or a derivative thereof, comprising the steps of a) contacting a B-
cell sample of an animal, preferably a mouse, which has been immunized with the
antigen with labeled
antigen, b) isolating individual cells from that sample that are CD19 positive, are CD138 negative, having bound the labeled antigen, c) determining the
nucleic acid sequences of a plurality of expressed genes, preferably, the entire
transcriptome for each of said isolated individual cells, d) selecting individual memory B-cells among the individual isolated cells by identifying the presence of
nucleic acid sequences of one or more expressed genes selected from the group consisting of: BhIhe41, Parm1, CD80, CobI, IgG1, Sspn, Ackr2, Nt5e, and Mki67 within the
nucleic acid sequences of a plurality of expressed genes, e) assembling
antibody light and heavy variable chain encoding nucleic acid sequences from the
nucleic acid sequence of the plurality of expressed genes of the selected individual memory B-cells, and f) expressing the
antibody light and
heavy chain encoding nucleic acid sequences assembled in step e) in a host
cell in order to manufacture the antibody.