Leukemia-associated changes identified by quantitative flow cytometry. III. B-cell gating in CD37/kappa/lambda
R E Peters1, G Janossy, K Ivory
1Department of Clinical Immunology, Royal Free Hospital School of Medicine, London, UK.
Insights
CD37 antigen expression is a reliable marker for identifying malignant B cells in blood and bone marrow. This method aids in detecting B-cell disorders like lymphomas and leukemia with high sensitivity.
Area of Science:
- Immunology
- Hematology
- Oncology
Background:
- CD37 is an antigen expressed on B-lymphoid cells.
- Accurate identification of malignant B cells is crucial for diagnosis and treatment of B-cell malignancies.
Purpose of the Study:
- To evaluate the utility of CD37 antigen expression for identifying malignant B cells.
- To assess the diagnostic value of CD37 in combination with kappa/lambda light chain staining.
Main Methods:
- Three-color immunofluorescence and quantitative immunofluorescence (QIFI test) were used to study CD37 expression.
- Kappa/lambda light chain staining was performed in conjunction with CD37 analysis.
- Analysis was conducted on normal peripheral blood, bone marrow, and various B-cell disorders.
Main Results:
- Normal peripheral B cells showed bright CD37 expression.
- Moderate to high CD37 levels were detected in most B-cell disorders, including B-ALL, lymphomas, and B-CLL.
- CD37 negativity or dull expression was observed in precursor B-ALL and non-B malignancies.
- CD37+ B-cell gating combined with kappa/lambda analysis identified monoclonality and aberrant immunoglobulin expression in B-cell malignancies.
- The test detected minimal B-cell involvement in bone marrow and circulating lymphoma cells.
Conclusions:
- CD37+ B-cell gating and kappa/lambda analysis is a sensitive and simple routine test for identifying malignant B cells.
- This method is effective for detecting B-cell malignancies in minimally involved bone marrow and blood.
- The test aids in diagnosing B-cell disorders and monitoring minimal residual disease.
Abstract:
Normal and malignant B-lymphoid cells were studied for CD37 antigen expression with three-color immunofluorescence (IF) in combination with kappa/lambda light chain staining, and by quantitative immunofluorescence utilizing the QIFI test. Peripheral B cells brightly expressed CD37 antigen (median 80-114 x 10(3) molecules/cell). Moderate to high levels (> 20 x 10(3)/cell) of CD37 expression were detected in 364 in 366 cases of peripheral B-cell disorders including all cases of B-ALL, B-cell lymphomas and B-CLL as well as eight of ten cases of PLL. By contrast, slg- B-cell precursors and other cell types in normal bone marrow (BM) were CD37-/CD37dull (< 10 x 10(3) molecules/cell). The negativity for CD37 or only CD37dull expression was confirmed in 180 of 182 cases of precursor B-ALL and 196 cases of non-B malignancies. Among the CD37 cluster, the RFB7 antibody of IgM class showed the weakest binding to non-B cells. In 64 normal samples of blood and BM the CD37+ gated cells showed normal kappa/lambda ratios as expected, while in 100 cases of B malignancy striking changes such as kappa/lambda monoclonality (79%) and aberrant slg- or sigdull expression (21%) were seen among the gated CD37+ B cells. The CD37/kappa/lambda test identified as few as 0.5% kappa+ or lambda- monoclonal B cells admixed to normal BM: circulating B-lymphoma cells were seen in nine patients with morphologically normal blood count. The discrimination of the Kolmogorov-Smirnov (KS) test for kappa/lambda excess was also improved by CD37+ B gating. Thus CD37+ B-cell gating and kappa/lambda analysis is a simple and sensitive routine test, e.g. when combined with autogating on a Cytoron-Absolute cytometer, for identifying malignant B cells in minimally involved BM and blood.
