Abstract: The invention provides recombinant antibody molecules comprising antigen binding regions derived from the heavy and/or light chain variable regions of a donor anti-CD3 antibody, e.g. OKT3, and which have anti-CD3 binding specificity, preferably of affinity similar to that of OKT3. The recombinant antibody is preferably a humanized antibody and may be a chimeric or CDR-grafted antibody. A method is disclosed for preparing CDR-grafted humanized antibodies in which, in addition to the CDR's non-human antibody residues are preferably used at positions 23, 24, 49, 71, 73 and 78 of the heavy chain variable region and at positions 46, 48, 58, and 71 of the light chain variable region. The recombinant, especially the humanized, anti-CD3 antibodies may be used for in vivo therapy or diagnosis.

Abstract: The invention provides recombinant antibody molecules comprising antigen binding regions derived from the heavy and/or light chain variable regions of a donor anti-CD3 antibody, e.g. OKT3, and which have anti-CD3 binding specificity, preferably of affinity similar to that of OKT3. The recombinant antibody is preferably a humanized antibody and may be a chimeric or CDR-grafted antibody. A method is disclosed for preparing CDR-grafted humanized antibodies in which, in addition to the CDR's, non-human antibody residues are preferably used at positions 23, 24, 49, 71, 73 and 78 of the heavy chain variable region and at positions 46, 48, 58, and 71 of the light chain variable region. The recombinant, especially the humanized, anti-CD3 antibodies may used for in vivo therapy or diagnosis.