THE DIVERSITY OF ANTIGEN-SPECIFIC MONOCLONAL-ANTIBODIES FROM TRANSGENIC MICE BEARING HUMAN-IMMUNOGLOBULIN GENE MINILOCI

An approach to the preparation of antigen-specific human monoclonal an tibodies focuses on mice transgenic for human immunoglobulin gene mini loci; the V gene segments in these miniloci undergo productive rearran gement to yield mouse B cells expressing human immunoglobulin (Ig) cha ins. The general usefulness of this strategy hinges on whether it is f easible to obtain specific, high-affinity antibodies following immuniz ation of such animals with a variety of antigens. To test this, we hav e investigated the antigen-specific responses in mice which carry huma n IgH miniloci (constaining just one or two VH segments) instead of a functional mouse IgH locus. Although serum responses were relatively w eak, monoclonal antibodies were readily obtained to all immunogens tes ted (a hapten, foreign proteins and human lymphoma cells). The affinit ies of two of the hapten-specific (anti-2-phenyl-oxazol-5-one) antibod ies were 60 and 160 nM, values intermediate between what is typically obtained in the primary and secondary response of normal mice. Sequenc e analysis of the rearranged V genes revealed that junctional events m ade a major contribution to diversity with a considerable amount of ap parently non-templated sequence at the V-D and D-J borders. Somatic hy permutation was also evident within the expressed V gene segments of m any of the antigen-specific hybridomas. These findings augur well for the general usefulness of the transgenic approach for the isolation of high-affinity human antibodies to a wide range of antigens and sugges ts that the miniloci need not be particularly large.