CD56 identifies monocytes and not natural killer cells in rhesus macaques

Cytometry. 1999 Sep 1;37(1):41-50.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Biomarkers / blood
  • CD56 Antigen / analysis
  • CD56 Antigen / immunology*
  • CD8 Antigens / analysis
  • CD8 Antigens / immunology
  • Cell Separation
  • Chromium Radioisotopes
  • Cytotoxicity Tests, Immunologic
  • Female
  • Flow Cytometry
  • Humans
  • Immunohistochemistry
  • Killer Cells, Natural / chemistry*
  • Lipopolysaccharide Receptors / analysis
  • Lipopolysaccharide Receptors / immunology
  • Macaca mulatta / blood*
  • Male
  • Monocytes / chemistry*
  • Receptors, IgG / blood
  • Receptors, IgG / immunology
  • Tumor Cells, Cultured / immunology


  • Biomarkers
  • CD56 Antigen
  • CD8 Antigens
  • Chromium Radioisotopes
  • Lipopolysaccharide Receptors
  • Receptors, IgG