title: Re-examination of the McCoy cell line for confirmation of its mouse origin: karyotyping, electron microscopy and reverse transcriptase assay for endogenous retrovirus.
abstract: BACKGROUND
  The McCoy cell line originally derived from human synovial fluid in 1955, has been later found useful for cultivation of Chlamydia trachomatis. This cell line has been subcultured and exchanged between laboratories for many years. In recent years, the McCoy cell line has been widely used in many clinical diagnostic laboratories and has been supplied through commercial companies for the isolation and identification of Chlamydia trachomatis from clinical specimens.
  
  
  OBJECTIVE
  Since retrovirus-like particles have been observed in McCoy cells and the species of origin of the currently used cell line has not been adequately documented, further characterization of McCoy cell line obtained from commercial sources was carried out.
  
  
  METHODS
  This study includes karyotypes analysis using G-banding for the confirmation of species origin of McCoy cells, electron microscopy for examination of virus particles associated with the cells and biochemical assay for reverse transcriptase activity for detection of retrovirus.
  
  
  RESULTS
  Our results showed by karyotype analysis that McCoy cells are of mouse origin. Electron microscopic examination revealed the presence of endogenous retrovirus type-A and type-C virions. Biochemical assays of culture supernatant fluids from McCoy cells detected reverse transcriptase activity which required Mg(2+) ions.
  
  
  CONCLUSIONS
  The present study has confirmed that McCoy cells currently used by many laboratories are mouse cells, not the original McCoy cells derived from human cells. Laboratory workers should be aware of the presence of endogenous murine retrovirus in this cell line and appropriate precautions should be taken.
authors.affiliation: Virology Reference Laboratory, Department of Veterans Affairs Medical Center, West Haven, CT, USA.
authors.forename: C K
authors.initials: CK
authors.lastname: Fong
authors.forename: T L
authors.initials: TL
authors.lastname: Yang-Feng
authors.forename: M B
authors.initials: MB
authors.lastname: Lerner-Tung