UNALTERED IMMUNOGLOBULIN EXPRESSION IN HYBRIDOMA CELLS MODIFIED BY TARGETING OF THE HEAVY-CHAIN LOCUS WITH AN INTEGRATION VECTOR

Chimeric antibodies against the murine T-cell antigen Thy-1.2 were gen erated in amounts sufficient for in vivo studies by substituting the c onstant gene segments via homologous recombination in the hybridoma ce ll. We show that an integration vector targets the heavy chain locus a t high frequency even in a non-isogenic situation. Using this vector t ype, for the first time expression rates were obtained that were ident ical to the parental hybridoma. The use of the gpt selection marker se ems to be crucial for efficient expression, and may overcome a recentl y claimed drawback of vector integration. A chimeric antibody produced by gene targeting was characterized in vitro and in vivo.