many chimeric protein drugs are monoclonal antibodies whose specificity for a target molecule was developed using mice and hence were initially "mouse" antibodies. as non-human proteins, mouse antibodies tend to evoke an immune reaction if administered to humans. the chimerization process involves engineering the replacement of segments of the antibody molecule that distinguish it from a human antibody. for example, human constant domains can be introduced, thereby eliminating most of the potentially immunogenic portions of the drug without altering its specificity for the intended therapeutic target. antibody nomenclature indicates this type of modification by inserting "-xi-" into the non-proprietary name (e.g., abci-"xi"-mab). if parts of the variable domains are also replaced by human portions, "humanized" antibodies are obtained. although not conceptually distinct from chimeras, this type is indicated using "-zu-" such as in dacli-"zu"-mab. see the list of monoclonal antibodies for more examples.