CD3 bright lymphocyte population reveal gammadelta T cells

Cytometry B Clin Cytom. 2004 Sep;61(1):45-53. doi: 10.1002/cyto.b.20005.

Abstract

Background: In routine CD3/CD4/CD8 T-cell analysis, a CD3 bright population of lymphocytes is frequently observed. The aim of the present study was to identify the immunological significance of such CD3 bright lymphocytes.

Methods: We analyzed samples from 31 healthy adult volunteers, 78 human immunodeficiency virus (HIV)-positive, and 78 renal transplanted patients.

Results: A clearly distinct CD3 bright (frequently CD4-/CD8-) T-cell fraction was observed in 84% of donors and was directly correlated with the fraction of gammadelta T cells (r2 = 0.64). CD3 overexpression on gammadelta T cells was confirmed by a combination of monoclonal antibody staining (CD3-ECD, gammadeltaTCR-FITC, and alphabetaTCR-PE-Cy5) or immunomagnetic purification of gammadelta T cells (i.e., MdFI 20 vs 8.86). The gammadelta T cells expressed CD8 polypeptide chains (alpha and beta) in all possible combinations. The largest proportion, surprisingly, were cells expressing CD8betabeta homodimers (43.8 +/- 16.5%). CD8alphaalpha homodimers were expressed on 14.2% (+/- 12.3) of total gammadelta T cells, whereas CD8alphabeta heterodimers were expressed on 12.2% (+/- 7.5). We also observed a bimodal distribution of the intensity of CD3 fluorescence of gammadelta T cells in immunocompromised patients with a threshold at 105 cell/microl. CD3 bright gammadelta T cells were more frequently observed in HIV patients (29%) compared with renal transplant patients (11%) and healthy donors (3%; chi2 test: P = 0.0007).

Conclusions: The simple observation of a CD3 bright T-cell subset on CD3/CD4/CD8 routine analysis suggests a high gammadelta T-cell fraction and, in our opinion, should be followed by a complementary analysis to determine precisely the number of gammadelta T cells and to identify their CD8alpha/beta phenotype. When CD3 bright T cells/microl were more than 40%, high gammadelta T cells were detected in more than 87% of cases, with a specificity of 76%. Occasionally, the CD3 bright subset appeared to be strongly homogeneous, suggesting an oligoclonal proliferation that could possibly reveal a chronic localized stimulation or an early lymphoproliferative disorder. Because the gammadelta T cells have interesting immunological peculiarities, the clinical significance of their quantitative abnormality should be clarified in diseases such as HIV, organ transplantation, autoimmunity and lymphoma.

MeSH terms

  • Adult
  • Antibodies, Monoclonal / chemistry
  • CD3 Complex / biosynthesis*
  • CD4 Antigens / biosynthesis
  • CD8 Antigens / biosynthesis
  • Dimerization
  • Female
  • HIV Seropositivity
  • Humans
  • Immunomagnetic Separation / methods*
  • Immunophenotyping / methods*
  • Kidney Transplantation / methods
  • Lymphocytes / cytology*
  • Lymphocytes / metabolism
  • Magnetics
  • Male
  • Middle Aged
  • Organ Transplantation
  • Phenotype
  • Receptors, Antigen, T-Cell, gamma-delta / biosynthesis
  • T-Lymphocyte Subsets
  • T-Lymphocytes / cytology*

Substances

  • Antibodies, Monoclonal
  • CD3 Complex
  • CD4 Antigens
  • CD8 Antigens
  • Receptors, Antigen, T-Cell, gamma-delta