The murine monoclonal antibody anti-cytokeratin CAM 5.2 is specific for intracellular cytokeratin 8, not cytokeratin 18

To the Editor:

We read with great interest the contribution by Grotenhuis and colleagues regarding the article entitled “The sentinel node concept in adenocarcinomas of the distal esophagus and gastroesophageal junction.”1 However, the authors might have inadvertently annotated the NCL 5D3 clone to be the source of the murine monoclonal antibody CAM 5.2 and unsuitably suggested CAM 5.2 to be specific to cytokeratins 8 and 18 in their experiment as well.1

We would like to comment and clarify that anti-cytokeratin CAM 5.2 was different from cytokeratin 8/18 monoclonal antibody. Monoclonal antibody to cytokeratin 8/18, instead of anti-cytokeratin CAM 5.2, was originally developed and manufactured by Novocastra Laboratories Ltd (Newcastle Upton Tyne, United Kingdom) using the brand Novocastra. The company grew and in 2003 was integrated into Vision BioSystems (Wetzlar, Germany). Today, Novocastra has become an important part of the overall histology range of Leica Microsystems' Biosystems Division through this definitive merger.

Therefore, monoclonal antibody to cytokeratin 8/18 is produced by Leica Microsystems' Biosystems Division, which is derived from the 5D3 clone. This clone reacts with human cytokeratin-intermediate filament proteins at 52.5 and 45 kd, which are identified as cytokeratins 8 and 18, respectively.2 On the other hand, anti-cytokeratin CAM 5.2 reagent is produced by Becton Dickinson Biosciences (Franklin Lakes, NJ) and is derived from the clone CAM 5.2. This clone reacts with human cytokeratin-intermediate filament proteins at 48 and 52 kd, which are identified as cytokeratins 7 and 8, respectively.3 In addition, Becton Dickinson Biosciences (1977) revised the data sheet for anti-cytokeratin CAM 5.2 to have a primary reactivity with cytokeratin 8 and, in addition, a weaker but distinct reactivity with cytokeratin 7. The data sheet also shows that there is no reactivity with cytokeratins 18 or 19. As a result, CAM 5.2 is not synonymous with cytokeratins 8 and 18.4 We concluded that the murine monoclonal antibody CAM 5.2 will not be specific for intracellular cytokeratins 8 and 18.