MeMo® is a transgenic mouse that produces human antibodies upon immunization and that are engineered for ease of antibody lead selection and development. All MeMo® -derived antibodies are encoded by a sLC V region that lacks T cell epitopes for low immunogenicity. A rearranging human heavy chain locus has been inserted in MeMo® that comprises all D and J gene segments, as well as a cohort of V gene segments selected for structural diversity, stability and frequent use in natural immune repertoires. In MeMo®, murine constant regions genes and control elements have been retained resulting in normal B cell development and robust immune responses. Monoclonal sLC antibodies derived from MeMo® can be applied as conventional human antibody therapeutics and are suitable for insertion in the COBRA™ and HYDRA™ platforms to create innovative antibody formats.