Double-labeling for keratin and class III β-tubulin within cultured retinal pigment epithelial cells: Comparison of chromogens to yield maximum resolution of two structural proteins within the same cell

Stanley A. Vinores, Melissa A. Vinores, Charlie Chiu, Thomas M. Woerner, Peter A. Campochiaro

Research output: Contribution to journalArticle


Previous attempts at colocalization of 2 distinct antigens within the same cell have met with various limitations. Either the double-labeling preparation was not permanent and required a fluorescent microscope (immunofluorescence) or I chromogen would totally or partially obscure the other, making resolution of both markers difficult. The present study was conducted to assess different combinations of chromogens for optimal colocalization of 2 structural proteins, keratin and class III β-tubulin, within cultured retinal pigment epithelial cells. The preferred combination of chromogens was HistoMark Red/HistoMark Blue. Good results were also achieved with HistoMark Red/ 3,3'-diamino-benzidine-HCl (DAB) or True Blue, HistoMark Blue/DAB, 3-amino-9-ethylcarbazole (AEC) or HistoMark Orange, and HistoMark Orange/ HistoMark Black or True Blue. It was unimportant which chromogen was used to localize each protein, but the order in which the chromogens were developed was important since some chromogens would wash out or diminish in clarity through subsequent incubations. The sequence of the chromogen application should be DAB first, then HistoMark Red, HistoMark Blue, AEC or Histo-Mark Orange, HistoMark Black, and lastly, 4-chloro-1- naphthol or True Blue.

Original languageEnglish (US)
Pages (from-to)19-26
Number of pages8
JournalJournal of Histotechnology
Issue number1
StatePublished - Jan 1 1997



  • chromogens
  • class III β-tubulin
  • double-labeling
  • epithelial cells
  • immunohistochemistry
  • keratin
  • retinal pigment epithelial cells

ASJC Scopus subject areas

  • Anatomy
  • Histology
  • Medical Laboratory Technology

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