Humanized antibodies

Humanized antibodies or chimeric antibodies are a type of monoclonal antibody that have been synthesized using recombinant DNA technology to circumvent the clinical problem of immune response to foreign antigens. The standard procedure of producing monoclonal antibodies yields mouse antibodies. Although murine antibodies are very similar to human ones there are differences, and the human immune system recognizes mouse antibodies as foreign, rapidly removing them from circulation and causing systemic inflammatory effects.

Humanized antibodies are produced by merging the DNA that encodes the binding portion of a monoclonal mouse antibody with human antibody-producing DNA. One then uses mammalian cell cultures to express this DNA and produce these half-mouse and half-human antibodies that are not as immunogenic as the murine variety.

Alternatives
A solution to this problem would be to generate human antibodies directly from humans. However, this is not easy, primarily because it is clearly not ethical to challenge humans with antigen in order to produce antibody. Furthermore, it is not easy to generate human antibodies against human tissues.