Hairy cell leukemia: early immunophenotypical detection and quantitative analysis by flow cytometry.
The abnormal coexpression of the so-called 'HCL-restricted' markers (CD22+CD11c, CD25 and CD103) identified on monotypic, slightly large B-lymphocytes in the large cell-gate of dot-plots has previously been shown to be highly characteristic of hairy cell leukemia (HCL). The main aim of our present study was to determine if patterns with low levels of neoplastic cells in bone marrow (BM) or peripheral blood (PB) are of a value the early diagnosis and/or detection of minimal residual disease (MRD) in HCL. Next we wished to determine if quantitative immunophenotyping given by molecules of equivalent soluble fluoresceine (MESF) could help to distinguish pathologic B-lymphocytic pool from that of normal residual B-cells also in patients with low numbers of HCL cells. The abnormal immunophenotypes were studied in 174 specimens from 19 patients with suspect HCL or during follow-up of already treated patients. For evaluation of marker density fluorescent calibration microbeads were used. In 12 HCL patients (67%) permanent complete remission was observed after treatment. In 6 patients (33%) transient MRD+ phenotype was identified but the clinical manifestation of relapse was followed till now in only three patients. One patient was phenotyped just only at diagnosis. The pathological cells in low levels were found in 5 patients at diagnosis (in the range from 2 to 12%) and in patients with MRD+ phenotype they were recognized repeatedly in the range from 2 to 8%. Furthermore, we observed in hairy cells significantly higher values of molecule numbers of some B-cell markers, comparing to that of residual B-cells in nonleukemic lymphocyte gate of the same sample. We found profound and persistent CD4+ lymphopenia in all but one studied patients after CdA treatment.


CONCLUSIONS
Flow cytometric immunophenotyping of PB and BM is highly sensitive and specific method and is capable to detect low levels of malignant cells in HCL. Quantitative analysis of MESF values of pathological B-cells comparing to normal residual B-cells seems to be another new marker of HCL in common, which is reliable detecting also small cell numbers in examined sample. A long-term decline of CD4+ T-cells correlated with the relatively low incidence of clinical progression of HCL.
Babusíková
O
O
Cancer Research Institute; Slovak Academy of Sciences, 833 91 Bratislava, Slovak Republic. exonobab@savba.sk
Tomová
A
A
D015703:Antigens, CD / Q000097:blood; D001402:B-Lymphocytes / Q000276:immunology* / Q000473:pathology; D015415:Biomarkers / Q000097:blood; D001854:Bone Marrow Cells / Q000276:immunology / Q000473:pathology; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D016130:Immunophenotyping / Q000379:methods*; D007943:Leukemia, Hairy Cell / Q000276:immunology* / Q000473:pathology; D008213:Lymphocyte Activation; D008297:Male
D015703:Antigens, CD; D015415:Biomarkers