Understanding the reconstitution of the B-cell compartment in bone marrow and blood after treatment for B-cell precursor acute lymphoblastic leukaemia

Early B cells repopulation in multiple sclerosis patients treated with rituximab is not predictive of a risk of relapse or clinical progression

BACKGROUND

It is currently unknown whether early B cell reconstitution (EBR) in MS patients under rituximab is associated with a risk of relapse or progression.

OBJECTIVES

Analyzing EBR in rituximab-treated patients and its putative association with clinical findings.

METHODS

Prospective lymphocytes immunophenotyping was performed in a monocentric cohort of MS patients treated by rituximab for 2 years. EBR was defined when B cells concentration was > 5 cells/mm3. B cell subsets were retrospectively associated with clinical data. Clinical and radiological monitoring included relapses, EDSS (Expanded Disability Status Scale), SDMT (Symbol Digit Modalities Test), and MRI.

RESULTS

182 patients were analyzed (61 remitting-relapsing and 121 progressive-active). 38.5% experienced EBR at least once, but very few (7/182) showed systematic reconstitution. Most patients remained stable upon treatment, regardless of the occurrence of EBR. Dynamics of B cell reconstitution featured increased naïve/transitional B cells, and decreased memory subsets. Homeostasis of the B cell compartment differed at baseline between patients experiencing or not EBR upon treatment. In patients with EBR, reciprocal dynamics of transitional and pro-inflammatory double-negative B cell subsets was associated with better response to rituximab treatment.

CONCLUSION

EBR is common in rituximab-treated MS patients and is not associated with clinical disease activity. EBR in the peripheral blood may reflect regulatory immunological phenomena in subgroup of patients.

Quality Assessment of a Large Multi-Center Flow Cytometric Dataset of Acute Myeloid Leukemia Patients-A EuroFlow Study

Flowcytometric analysis allows for detailed identification and characterization of large numbers of cells in blood, bone marrow, and other body fluids and tissue samples and therefore contributes to the diagnostics of hematological malignancies. Novel data analysis tools allow for multidimensional analysis and comparison of patient samples with reference databases of normal, reactive, and/or leukemia/lymphoma patient samples. Building such reference databases requires strict quality assessment (QA) procedures. Here, we compiled a dataset and developed a QA methodology of the EuroFlow Acute Myeloid Leukemia (AML) database, based on the eight-color EuroFlow AML panel consisting of six different antibody combinations, including four backbone markers. In total, 1142 AML cases and 42 normal bone marrow samples were included in this analysis. QA was performed on 803 AML cases using multidimensional analysis of backbone markers, as well as tube-specific markers, and data were compared using classical analysis employing median and peak expression values. Validation of the QA procedure was performed by re-analysis of >300 cases and by running an independent cohort of 339 AML cases. Initial evaluation of the final cohort confirmed specific immunophenotypic patterns in AML subgroups; the dataset therefore can reliably be used for more detailed exploration of the immunophenotypic variability of AML. Our data show the potential pitfalls and provide possible solutions for constructing large flowcytometric databases. In addition, the provided approach may facilitate the building of other databases and thereby support the development of novel tools for (semi)automated QA and subsequent data analysis.

VS38c and CD38-Multiepitope Antibodies Provide Highly Comparable Minimal Residual Disease Data in Patients With Multiple Myeloma

Objectives

To compare flow cytometric minimal residual disease (MRD) data obtained using the EuroFlow approach, including the CD38-multiepitope (ME) antibody or the VS38c antibody.

Methods

We evaluated 29 bone marrow samples from patients with multiple myeloma (MM), of whom 15 had received daratumumab within the past 6 months. We evaluated MRD data and fluorescence intensities.

Results

Qualitative MRD data were 100% concordant between the 2 approaches. In MRD-positive samples (n = 14), MRD levels showed an excellent correlation (R² = 0.999). Whereas VS38c staining was strong in both normal plasma cells and MM cells, independent of daratumumab treatment, staining intensities for CD38 were lower in MM cells compared with normal plasma cells, and on both cell types CD38 expression was significantly reduced in daratumumab-treated patients.

Conclusions

Both CD38-ME and VS38c allow reliable MRD detection in MM patients, but the high expression of VS38c allows easier identification of MM cells, especially in daratumumab-treated patients.

B-Cell Regeneration Profile and Minimal Residual Disease Status in Bone Marrow of Treated Multiple Myeloma Patients

B-cell regeneration during therapy has been considered as a strong prognostic factor in multiple myeloma (MM). However, the effects of therapy and hemodilution in bone marrow (BM) B-cell recovery have not been systematically evaluated during follow-up. MM (n = 177) and adult (≥50y) healthy donor (HD; n = 14) BM samples were studied by next-generation flow (NGF) to simultaneously assess measurable residual disease (MRD) and residual normal B-cell populations. BM hemodilution was detected in 41 out of 177 (23%) patient samples, leading to lower total B-cell, B-cell precursor (BCP) and normal plasma cell (nPC) counts. Among MM BM, decreased percentages (vs. HD) of BCP, transitional/naïve B-cell (TBC/NBC) and nPC populations were observed at diagnosis. BM BCP increased after induction therapy, whereas TBC/NBC counts remained abnormally low. At day+100 postautologous stem cell transplantation, a greater increase in BCP with recovered TBC/NBC cell numbers but persistently low memory B-cell and nPC counts were found. At the end of therapy, complete response (CR) BM samples showed higher CD19^- nPC counts vs. non-CR specimens. MRD positivity was associated with higher BCP and nPC percentages. Hemodilution showed a negative impact on BM B-cell distribution. Different BM B-cell regeneration profiles are present in MM at diagnosis and after therapy with no significant association with patient outcome.

Immunophenotypic shift in the B-cell precursors from regenerating bone marrow samples: A critical consideration for measurable residual disease assessment in B-lymphoblastic leukemia

Accurate knowledge of expression patterns/levels of commonly used MRD markers in regenerative normal-B-cell-precursors (BCP) is highly desirable to distinguish leukemic-blasts from regenerative-BCP for multicolor flow cytometry (MFC)-based measurable residual disease (MRD) assessment in B-lymphoblastic leukemia (B-ALL). However, the data highlighting therapy-related immunophenotypic-shift in regenerative-BCPs is scarce and limited to small cohort. Herein, we report the in-depth evaluation of immunophenotypic shift in regenerative-BCPs from a large cohort of BALL-MRD samples. Ten-color MFC-MRD analysis was performed in pediatric-BALL at the end-of-induction (EOI), end-of-consolidation (EOC), and subsequent-follow-up (SFU) time-points. We studied normalized-mean fluorescent intensity (nMFI) and coefficient-of-variation of immunofluorescence (CVIF) of CD10, CD19, CD20, CD34, CD38, and CD45 expression in regenerative-BCP (early, BCP1 and late, BCP2) from 200 BALL-MRD samples, and compared them with BCP from 15 regenerating control (RC) TALL-MRD samples and 20 treatment-naïve bone-marrow control (TNSC) samples. Regenerative-BCP1 showed downregulation in CD10 and CD34 expression with increased CVIF and reduced nMFI (p < 0.001), upregulation of CD20 with increased nMFI (p = 0.014) and heterogeneous CD45 expression with increased CVIF (p < 0.001). Immunophenotypic shift was less pronounced in the BCP2 compared to BCP1 compartment with increased CVIF in all but CD45 (p < 0.05) and reduced nMFI only in CD45 expression (p = 0.005). Downregulation of CD10/CD34 and upregulation of CD20 was higher at EOI than EOC and SFU time-points (p < 0.001). Regenerative-BCPs are characterized by the significant immunophenotypic shift in commonly used B-ALL-MRD markers, especially CD10 and CD34 expression, as compared to treatment-naïve BCPs. Therefore, the templates/database for BMRD analysis must be developed using regenerative-BCP.