GENERATION OF CHIMERIC MONOCLONAL-ANTIBODIES FROM MICE THAT CARRY HUMAN-IMMUNOGLOBULIN-C-GAMMA-1 HEAVY OR C-KAPPA LIGHT-CHAIN GENE SEGMENTS

Gene targeting in mouse embryonic stem (ES) cells was used to replace (i) the mouse immunoglobulin heavy chain (IgH) C gamma 2a gene segment (mC gamma 2a) with the human C gamma 1 gene segment (hC gamma 1), and (ii) the mouse immunoglobulin light chain (IgL) C kappa gene segment (mC kappa) with its human counterpart (bC kappa). ES cells carrying th ese gene conversions were used to generate chimeric mice that transmit ted the human alleles through the germ line. Mice homozygous for both gene alterations were generated by breeding. Serum from homozygous mut ant mice contained comparable amounts of antibodies with chimeric kapp a or mouse lambda light chains but only small fractions of basal serum IgG or antibodies elicited against immunizing agents contained chimer ic heavy chains. A relative increase in immunogen-specific hC gamma 1 antibodies was seen following immunization in combination with the sap onin adjuvant QS-21. The effect of this was to shift the IgG1-dominate d response to an IgG subclass profile that included significant amount s of IgG2a, IgG2b and IgG3 and chimeric IgG. The amounts of antibody s ecreted by hybridomas derived from mutant and wild-type mice were simi lar. Sequencing confirmed correct splicing of hC gamma 1 and hC kappa gene segments to mouse J gene segments in hybridoma Ig gene transcript s. in conclusion, IgHhC gamma 1/IgLhC kappa double mutant mice provide a useful animal model for deriving humanized antibodies with potentia l applications in immunotherapy and diagnostics in vivo as well as for investigating hC gamma 1 associated functions. (C) 1998 Published by Elsevier Science B.V. All rights reserved.