Although mice antibodies are very similar to human antibodies, there is difference. Hence human immune system recognizes mouse antibodies as foreign and cause systemic inflammatory effects to remove them rapidly from circulation.
To overcome this problem antibodies must be produced directly in humans, but production of human antibodies directly in humans is not easy and not ethical also.
Hence to solve the immunogenicity problem, using recombinant DNA technology mice antibodies are modified to produce less immunogenic antibodies.
“Chimeric antibodies” and “humanized antibodies” are the two types of antibodies produced through recombinant DNA technology.
Humanized antibodies are produced through merging DNA that encodes the binding portion (Fab region) of mouse antibody with human antibody-producing DNA that encodes the remaining major part of the antibody.
This recombination results in the production of humanized antibodies that are not as immunogenic as the murine variety.
Even though a chimeric antibody is also a recombinant antibody it is different from humanized antibody because a major portion of chimeric antibody is coded by the mouse gene.
The recombinant DNA for chimeric antibody contains promoter, leader, and variable region sequences from a mouse antibody gene and constant region exons from a human antibody gene.