What is the interpretation of the T and B Cells by Flow Cytometry test, including specific antigen expression, such as Cluster of Differentiation (CD) markers, and the distinction between normal and abnormal expression, including dim and bright expression?

From the Guidelines

Flow cytometry is a crucial laboratory technique for evaluating lymphocyte populations, and the T and B Cells by Flow Cytometry test specifically assesses immune function by measuring T cells (CD3+), T cell subsets (CD4+ and CD8+), and B cells (CD19+ or CD20+). The test provides both numerical data, including absolute counts and percentages of each cell population, and information on antigen expression patterns, which can be described as normal, dim, bright, partial, or absent 1.

Key Components of the Test

• CD3+ T cells: normally 55-84% of lymphocytes
• CD4+ T cells: normally 31-60%
• CD8+ T cells: normally 13-41%
• CD19+ B cells: normally 6-23% Abnormal expression patterns, such as dim CD3 expression, can indicate T-cell dysregulation or certain T-cell lymphomas, while bright CD3 expression can be seen in T-cell activation 1.

Interpreting Results

When interpreting results, it is essential to look for both numerical abnormalities and unusual expression patterns.

• Low CD4+ counts might indicate HIV infection or other immunodeficiencies
• Abnormal CD4:CD8 ratios (normally >1) can suggest immune dysregulation
• Aberrant co-expression of markers (like T cells expressing B cell markers) often indicates lymphoproliferative disorders or leukemias The clinical context is crucial for proper interpretation, as temporary changes can occur during infections or with certain medications 1.

Clinical Significance

The T and B Cells by Flow Cytometry test is vital for diagnosing and monitoring various immune-related disorders, including lymphoproliferative disorders, leukemias, and immunodeficiencies.

• CLL cells, for example, co-express the T-cell antigen CD5 and B-cell surface antigens CD19, CD20, and CD23, with characteristically low levels of surface immunoglobulin, CD20, and CD79b compared to normal B cells 1
• The test can also help identify independent prognostic markers and assess minimal residual disease levels in patients with myeloma or other plasma cell disorders 1 By considering both numerical data and antigen expression patterns, clinicians can gain a comprehensive understanding of a patient's immune function and make informed decisions about diagnosis, treatment, and monitoring.

From the Research

Overview of Flow Cytometry

Flow cytometry is a laboratory technique used to analyze and sort cells based on their physical and chemical characteristics. In the context of T and B cell analysis, flow cytometry is used to identify and quantify different subsets of these cells.

T and B Cell Analysis by Flow Cytometry

The test "T AND B Cells by Flow Cytometry" typically involves analyzing a blood sample to identify and quantify different subsets of T and B cells. This is done by staining the cells with specific antibodies that bind to particular surface markers, such as CD3, CD4, CD8, and CD19 2, 3, 4.

Interpretation of Lab Results

The lab report for T and B cell analysis by flow cytometry typically includes numerical data, such as:

• Absolute counts of T and B cells (e.g., CD3+ cells, CD4+ cells, CD8+ cells, CD19+ cells)
• Percentage of T and B cells (e.g., %CD4, %CD8, %CD19)
• Expression of specific surface markers, such as CD3 dim or CD3 bright 5, 6

Normal vs. Abnormal Results

Normal results for T and B cell analysis by flow cytometry vary depending on the individual's age, sex, and other factors. Generally, a normal result would show:

• A normal absolute count and percentage of T and B cells
• Normal expression of surface markers, such as CD3, CD4, CD8, and CD19 Abnormal results may indicate:
• Immunodeficiency or immunosuppression (e.g., low absolute count of T or B cells)
• Autoimmune disorders (e.g., abnormal expression of surface markers)
• Infections or inflammation (e.g., elevated absolute count of T or B cells)

Specific Antigens and Their Expression

Some specific antigens and their expression are:

• CD3: a surface marker expressed on all T cells. Normal expression is typically bright, while dim expression may indicate immature or activated T cells 5, 6
• CD4: a surface marker expressed on helper T cells. Normal expression is typically bright, while dim expression may indicate activated or regulatory T cells 4
• CD8: a surface marker expressed on cytotoxic T cells. Normal expression is typically bright, while dim expression may indicate activated or regulatory T cells 4
• CD19: a surface marker expressed on B cells. Normal expression is typically bright, while dim expression may indicate immature or activated B cells 2

Example of Abnormal Results

For example, a lab report may show:

• Low absolute count of CD4+ cells (e.g., 200 cells/μL) and low percentage of CD4+ cells (e.g., 20%)
• Abnormal expression of CD3, with a high percentage of CD3 dim cells (e.g., 30%)
• Elevated absolute count of CD8+ cells (e.g., 1000 cells/μL) and high percentage of CD8+ cells (e.g., 50%)

These results would suggest an abnormal immune response, potentially indicating immunodeficiency or autoimmune disorders. However, interpretation of these results should be done by a qualified healthcare professional, taking into account the individual's medical history and other laboratory results 2, 3, 4, 5, 6.