SCYM Clinical Applications 4 — Questions and Answers
Question 1: Which marker is used to distinguish T-cell large granular lymphocyte (T-LGL) leukemia from reactive CD8+ T-cell expansions?
- TCR V-beta clonality by flow cytometry (Correct answer)
- Absolute CD8 count above 500 cells/μL
- CD56 coexpression on all CD8+ cells
- Loss of CD3 expression
Correct answer: TCR V-beta clonality by flow cytometry
TCR V-beta clonality analysis using a panel of V-beta-specific antibodies demonstrates clonal T-cell expansion, supporting LGL leukemia over reactive processes.
Question 2: In the context of solid organ transplantation, flow cytometry crossmatching (FCXM) detects which antibodies as clinically significant?
- Donor-specific HLA antibodies binding to T and B lymphocytes (Correct answer)
- Non-HLA MICA antibodies only
- Auto-antibodies to CD20 on recipient B cells
- Cytokine receptor antibodies on NK cells
Correct answer: Donor-specific HLA antibodies binding to T and B lymphocytes
FCXM detects donor-specific antibodies (DSAs) by incubating recipient serum with donor T and B lymphocytes and measuring fluorescent anti-human IgG binding.
Question 3: Which immunophenotype best characterizes Sézary syndrome cells detected in peripheral blood?
- CD4+/CD7-/CD26-/CD3+ T cells with high CD4:CD8 ratio (Correct answer)
- CD8+/CD56+/CD3- cytotoxic lymphocytes
- CD4+/CD25+/FoxP3+ regulatory T cells
- CD4+/CD30+/CD15+ Reed-Sternberg-like cells
Correct answer: CD4+/CD7-/CD26-/CD3+ T cells with high CD4:CD8 ratio
Sézary cells are neoplastic CD4+ T cells that characteristically lack CD7 and CD26, and are detected in blood with an elevated CD4:CD8 ratio.
Question 4: In diagnosing chronic lymphocytic leukemia (CLL), which score using CD5, CD23, CD22, FMC7, and surface Ig intensity is used?
- Matutes/Moreau CLL immunophenotype scoring system (Correct answer)
- IPSS-R prognostic scoring
- FLIPI follicular lymphoma score
- Ann Arbor clinical staging
Correct answer: Matutes/Moreau CLL immunophenotype scoring system
The Matutes score assigns points for CD5+, CD23+, weak CD22, FMC7-, and weak sIg; a score ≥4 is highly specific for CLL.
Question 5: In pediatric B-ALL, which antigen is most important for distinguishing normal hematogones from leukemic blasts?
- CD38 and CD58 expression patterns relative to normal B-cell precursors (Correct answer)
- CD34 positivity alone
- Absolute TdT fluorescence intensity
- CD10 expression level
Correct answer: CD38 and CD58 expression patterns relative to normal B-cell precursors
Leukemic B-ALL blasts typically show abnormal CD38 (bright) and CD58 (high) compared to normal hematogones, which follow predictable maturation-stage expression.
Question 6: Which flow cytometric marker is used to assess platelet function in patients with suspected Glanzmann thrombasthenia?
- CD41 (GPIIb) and CD61 (GPIIIa) surface expression (Correct answer)
- CD42b (GPIbα) surface expression only
- P-selectin (CD62P) upregulation after thrombin activation
- CD36 expression on platelets
Correct answer: CD41 (GPIIb) and CD61 (GPIIIa) surface expression
Glanzmann thrombasthenia results from deficiency of the GPIIb/IIIa complex (CD41/CD61), which is directly measurable by flow cytometry.
Question 7: When performing immunophenotyping for primary immunodeficiency, which panel is essential for evaluating X-linked agammaglobulinemia (XLA)?
- CD19+ B-cell quantification with near-absent peripheral B cells (Correct answer)
- CD4/CD8 T-cell subset ratio measurement
- NK cell CD56/CD16 panel
- CD25/FoxP3 regulatory T-cell panel
Correct answer: CD19+ B-cell quantification with near-absent peripheral B cells
XLA is characterized by a severe reduction or absence of circulating CD19+ B cells due to a BTK mutation affecting B-cell development.
SCYM Clinical Applications 4
Which marker is used to distinguish T-cell large granular lymphocyte (T-LGL) leukemia from reactive CD8+ T-cell expansions?