Neutropenia Associated With T-Cell Large Granular Lymphocyte Leukemia: Long-Term Response to Cyclosporine Therapy Despite Persistence of Abnormal Cells

Minimal Disease Detection and Confirmation in Hematologic Malignancies: Combining Cell Sorting with Clonality Profiling

Background: In this study we demonstrate the technical application of flow cytometry and cell sorting combined with gene-rearrangement clonality profiling to detect and confirm minimal disease in 2 leukemia and 2 lymphoma cases.

Methods: Specimens with low percentages (0.05%–5%) of abnormal lymphoid populations were identified by flow cytometry. The abnormal lymphoid populations were sorted by flow cytometry, and the purified tumor populations along with unsorted fractions were subsequently analyzed for the presence of clonal gene rearrangements by PCR and fluorescence-based capillary electrophoresis fragment analysis.

Results: In 3 cases, distinct clonality profiles could be detected in the purified tumor cell fraction, and suspicious amplicons of identical sizes were detected among the polyclonal backgrounds in the unsorted specimens. For 1 patient, a monoclonal signal was detected in the sorted tumor cell fraction but not in the unseparated bone marrow specimen containing 0.05% abnormal lymphoblasts. A subsequent bone marrow specimen containing 4.8% recurring leukemia cells tested positive with a clonality profile that matched the previous profile in the sorted cell population.

Conclusions: The described method integrating 2 technologies allows genotypic confirmation of an aberrant population detected by immunophenotype to increase diagnostic certainty. This strategy provides a sensitive tool for disease monitoring without the need for patient-specific primer design and assay optimization required for quantitative PCR analysis.

Chronic neutropenia mediated by Fas ligand

Chronic neutropenia, often associated with rheumatoid arthritis, is a characteristic finding in large granular lymphocyte (LGL) leukemia. The mechanism of neutropenia is not known. Normal neutrophil survival is regulated by the Fas–Fas ligand apoptotic system. We hypothesized that neutropenia in LGL leukemia is mediated by dysregulated expression of Fas ligand. Levels of Fas ligand in serum samples from patients with LGL leukemia were measured with a Fas ligand enzyme-linked immunosorbent assay. The effects of serum from patients with LGL leukemia on apoptosis of normal neutrophils were determined by flow cytometry and morphologic assessment. High levels of circulating Fas ligand were detected in 39 of 44 serum samples from patients with LGL leukemia. In contrast, Fas ligand was undetectable in 10 samples from healthy donors. Serum from the patients triggered apoptosis of normal neutrophils that depended partly on the Fas pathway. Resolution of neutropenia was associated with disappearance or marked reduction in Fas ligand levels in 10 of 11 treated patients. These data suggest that high levels of Fas ligand are a pathogenetic mechanism in human disease.