The HyHEL10 hybridoma produces an antibody that binds hen egg lysozyme peptide (HEL) with high affinity. The rearranged variable heavy gene segment from the HyHEL10 hybridoma replaced the endogenous J gene segments of the IgH locus. A floxed neomycin cassette was placed upstream for targeting purposes. About 0.4% of B cells produce antibody that bind HEL with high affinity. (J:132538)