Numerous antibodies against the HER 2 receptor are available commercially, including both polyclonal and monoclonal antibodies (eg, rabbit monoclonal clone 4B5 and mouse monclonal clone CB11). In general, monoclonal antibodies are considered more specific.
The antigenic domain of Food and Drug Administration (FDA)-approved antibodies is typically for the internal domain of the HER2 receptor. There is some concern that the external domain of HER2 may be more easily cleaved off (the external domain is the portion is measured by the serum ELISA assay). For this reason, some feel that antibodies against the external domain may not be as sensitive as antibodies against the internal domain.
However, despite the possibility of cleaving, there are a few commercially available antibodies against the external domain of HER2. Probably the most widely used external domain antibody is TAB250 (Zymed, South San Francisco, CA).