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Flow Cytometric Analysis of CD5+ B Cells
A Frame of Reference for Minimal Residual Disease Analysis in Chronic Lymphocytic Leukemia

Ritu Gupta MD, Paresh Jain MD, S.V.S. Deo MS, Atul Sharma MD, DM
DOI: http://dx.doi.org/10.1309/T5EM9BQUB9CM8F57 368-372 First published online: 1 March 2004

Abstract

Recent reports suggest that CD5+ B cells constitute up to 47% of the total B cells in normal peripheral blood (PB), a finding that would restrict the sensitivity of the CD5/CD19 flow cytometric assay for minimal residual disease (MRD) analysis in chronic lymphocytic leukemia (CLL). We studied 40 normal samples (PB, 20; bone marrow [BM], 20) using CD5–fluorescein isothiocyanate (FITC)/CD19-phycoerythrin (PE) immunostaining to evaluate the reference range of CD5+ B cells. The mean percentage of CD5+ B cells per total number of B cells was 12.2% (range, 3.6%–23.9%) in PB and 11.7% (range, 4.4%–19.5%) in BM. On serial dilution, this assay could detect 1 CLL cell in 1,000 leukocytes (sensitivity, 0.1%). A distinct “bright” CD5+ B-cell subpopulation, consistent with a CLL-like-phenotype, was observed in 3 samples. Our results suggest that the CD5-FITC/CD19-PE assay has a clinically useful sensitivity for MRD analysis in CLL. The usefulness of this assay as a screening tool to identify the earliest stage of indolent CLL needs further study.

Key Words:
  • CD5+ B cells
  • Flow cytometry
  • Chronic lymphocytic leukemia
  • Minimal residual disease