What are the normal and abnormal expressions of CD3, CD4, CD8, and CD19 antigens in a T and B Cells by Flow Cytometry test, specifically regarding their brightness and percentage?

From the Guidelines

Flow cytometry, specifically T and B Cells by Flow Cytometry, is a critical test for evaluating lymphocyte populations, where CD3, CD4, CD8, and CD19 markers should all show bright, distinct expression patterns on their respective cell populations. In a normal T and B cell flow cytometry report, these markers are expected to be brightly expressed: CD3 on all T cells, CD4 on helper T cells, CD8 on cytotoxic T cells, and CD19 on B cells 1. The report typically includes both the percentage of cells expressing each marker and the absolute count of these cells per microliter of blood.

Key Markers and Their Expression

• CD3: Should be brightly expressed on all T cells.
• CD4: Should be brightly expressed on helper T cells.
• CD8: Should be brightly expressed on cytotoxic T cells.
• CD19: Should be brightly expressed on B cells. Abnormal expression patterns might include dim expression, absent expression, or aberrant expression. For example, dim CD3 expression can indicate T-cell dysregulation or certain T-cell malignancies, as noted in guidelines for performing single-platform absolute CD4+ T-cell determinations 1.

Interpreting Test Results

When interpreting these tests, clinicians should look for both numerical abnormalities and qualitative changes in marker expression. The sum of the %CD3+CD4+ and %CD3+CD8+ cells should equal the total %CD3+ cells within plus or minus 5%, with a maximum variability of less than or equal to 10% 1.

Clinical Implications

For instance, in common variable immunodeficiency, one might see normal T cell markers but reduced B cell numbers with abnormal CD19 expression. In certain leukemias, one might observe abnormal brightness or dimness of markers that help distinguish malignant from normal cells. The expression pattern is as important as the numerical values for accurate diagnosis of immunodeficiencies, lymphoproliferative disorders, and monitoring immune reconstitution after treatments.

Quality Control and Assurance

The use of positive methodologic controls and positive controls for evaluating reagents is crucial for ensuring the accuracy and reliability of flow cytometry results, as outlined in guidelines for performing single-platform absolute CD4+ T-cell determinations 1.

Conclusion is not needed, the above is the answer.

From the Research

Flow Cytometry and T and B Cells

• Flow cytometry is a diagnostic tool used to evaluate immune function and identify underlying aberrant immune pathways 2.
• It allows for the analysis of T and B lymphocytes, which play a crucial role in the adaptive immune system.
• The test can be used to diagnose immunodeficiencies, monitor disease activity, and assess infection risk.

Interpretation of Lab Results

• The lab report typically includes numerical data, such as absolute and percentage values for CD3, CD4, CD8, and CD19.
• The report may also include information on the expression of these antigens, such as dim or bright expression.
• Normal expression of CD3, CD4, and CD8 is typically bright, while CD19 expression can be either dim or bright, depending on the B cell subset 3, 4.
• For example, CD19+ B cells can be further subdivided into subsets based on their expression of other antigens, such as CD20, CD21, and CD23.

Specific Antigens and Their Expression

• CD3: typically bright expression on T cells 3, 4.
• CD4: typically bright expression on T-helper cells 3, 4.
• CD8: typically bright expression on cytotoxic T cells 3, 4.
• CD19: can be either dim or bright expression on B cells, depending on the subset 5, 6.
• CD20: typically bright expression on mature B cells 5.
• CD21: typically bright expression on mature B cells 5.
• CD23: typically dim expression on mature B cells 5.

Abnormalities to Look for

• Abnormalities in the expression of these antigens can indicate immunodeficiencies or other immune disorders.
• For example, decreased expression of CD3, CD4, or CD8 can indicate T cell immunodeficiency 2.
• Decreased expression of CD19 or CD20 can indicate B cell immunodeficiency 5.
• Abnormal expression of CD21 or CD23 can indicate defects in B cell activation or differentiation 5.