title: CD56 identifies monocytes and not natural killer cells in rhesus macaques.
abstract: BACKGROUND
  CD56 is a lineage-specific marker of human natural killer (NK) cells. There are conflicts in the literature regarding the role of CD56 as a marker of NK cells in non-human primates. In the present study, we examined the role of CD56 in identifying rhesus NK cells.
  
  
  METHODS
  The immunophenotype of normal macaque and human NK cells was analyzed by two- and three-color flow cytometry. Flow cytometric cell sorting was subsequently used to deplete or purify NK cells; the resulting cell populations were then used in standard chromium release assays of NK lytic function.
  
  
  RESULTS
  In peripheral blood mononuclear cells of the rhesus macaque, CD56 was expressed primarily on cells with the light scatter and immunophenotypic profile of monocytes. Flow cytometric depletion of rhesus CD56(+) monocytic cells did not diminish functional activity against K562 cells, whereas depletion of CD8(+) or CD16(+) lymphocytes completely abrogated functional activity. Three-color flow cytometric analysis of CD8(+), CD16(+) lymphocytes showed that they expressed other markers (CD2, CD7, TIA-1) associated with NK cells, but notably, not CD56.
  
  
  CONCLUSIONS
  These studies demonstrate that CD56 is not suitable as a marker of NK cells in the rhesus macaque.
authors.affiliation: Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
authors.forename: D L
authors.initials: DL
authors.lastname: Carter
authors.forename: T M
authors.initials: TM
authors.lastname: Shieh
authors.forename: R L
authors.initials: RL
authors.lastname: Blosser
authors.forename: K R
authors.initials: KR
authors.lastname: Chadwick
authors.forename: J B
authors.initials: JB
authors.lastname: Margolick
authors.forename: J E
authors.initials: JE
authors.lastname: Hildreth
authors.forename: J E
authors.initials: JE
authors.lastname: Clements
authors.forename: M C
authors.initials: MC
authors.lastname: Zink
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000097:blood; D019002:CD56 Antigen / Q000032:analysis / Q000276:immunology*; D016827:CD8 Antigens / Q000032:analysis / Q000276:immunology; D002469:Cell Separation; D002860:Chromium Radioisotopes; D003601:Cytotoxicity Tests, Immunologic; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007150:Immunohistochemistry; D007694:Killer Cells, Natural / Q000737:chemistry*; D018950:Lipopolysaccharide Receptors / Q000032:analysis / Q000276:immunology; D008253:Macaca mulatta / Q000097:blood*; D008297:Male; D009000:Monocytes / Q000737:chemistry*; D017452:Receptors, IgG / Q000097:blood / Q000276:immunology; D014407:Tumor Cells, Cultured / Q000276:immunology
chemical_list: D015415:Biomarkers; D019002:CD56 Antigen; D016827:CD8 Antigens; D002860:Chromium Radioisotopes; D018950:Lipopolysaccharide Receptors; D017452:Receptors, IgG