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Published on: September 9, 2011
CD3 bright lymphocyte population reveal gammadelta T cells
Claude Lambert1, Christian Genin
1Immunology Laboratory, University Hospital, St. Etienne, France. claude.lambert@uni-st-etienne.fr
Insights
A CD3 bright T-cell population often indicates a high fraction of gammadelta T cells, which warrants further analysis. This finding is particularly relevant in immunocompromised patients like those with HIV or post-transplant.
Area of Science:
- Immunology
- Flow Cytometry
- T-cell Biology
Background:
- Routine CD3/CD4/CD8 T-cell analysis frequently reveals a distinct CD3 bright lymphocyte population.
- The immunological significance of these CD3 bright lymphocytes remains to be fully elucidated.
Purpose of the Study:
- To identify the immunological significance of CD3 bright lymphocytes.
- To correlate the presence of CD3 bright T-cells with gammadelta T-cell populations and their phenotypes.
Main Methods:
- Analysis of peripheral blood samples from healthy donors, HIV-positive patients, and renal transplant recipients.
- Flow cytometry using CD3, CD4, CD8, gammadeltaTCR, and alphabetaTCR antibodies.
- Immunomagnetic purification was used to confirm findings.
Main Results:
- A CD3 bright T-cell fraction, often CD4-/CD8-, was observed in 84% of individuals and strongly correlated with gammadelta T cells (r² = 0.64).
- Gammadelta T cells exhibited diverse CD8alpha/beta chain combinations, with CD8beta:beta homodimers being most prevalent (43.8%).
- CD3 bright gammadelta T cells were significantly more frequent in HIV patients (29%) compared to renal transplant patients (11%) and healthy donors (3%).
Conclusions:
- The presence of a CD3 bright T-cell subset suggests a high gammadelta T-cell fraction, necessitating further analysis of gammadelta T-cell numbers and CD8 phenotype.
- Elevated CD3 bright T cells (>40%) accurately indicated high gammadelta T cells in over 87% of cases.
- The clinical significance of quantitative gammadelta T-cell abnormalities warrants investigation in conditions like HIV, organ transplantation, and autoimmune diseases.
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.
