ANTIGEN-SPECIFIC HUMAN-ANTIBODIES FROM MICE COMPRISING 4 DISTINCT GENETIC MODIFICATIONS

HUMAN sequence monoclonal antibodies, which in theory combine high spe cificity with low immunogenicity, represent a class of potential thera peutic agents. But nearly 20 years after Kohler and Milstein first dev eloped methods for obtaining mouse antibodies(1), no comparable techno logy exists for reliably obtaining high-affinity human antibodies dire cted against selected targets.Thus, rodent antibodies(2), and in vitro modified derivatives of rodent antibodies(3-5), are still being used and tested in the clinic. The rodent system has certain clear advantag es; mice are easy to immunize, are not tolerant to most human antigens , and their B cells form stable hybridoma cell lines. To exploit these advantages, we have developed transgenic mice thatexpress human IgM, IgG and Ig kappa in the absence of mouse IgM or Ig kappa. We report he re that these mice contain human sequence transgenes that undergo V(D) J joining, heavy-chain class switching, and somatic mutation to genera te arepertoire of human sequence immunoglobulins. They are also homozy gous for targeted mutations that disrupt V(D)J rearrangement at the en dogenous heavy- andkappa light-chain loci. We have immunized the mice with human proteins and isolated hybridomas secreting human IgG kappa antigen-specific antibodies.