The European Myeloma Network (EMN) organized two flow cytometry workshops. The first aimed to identify specific indications for flow cytometry in patients with monoclonal gammopathies, and consensus technical approaches through a questionnaire-based review of current practice in participating laboratories. The second aimed to resolve outstanding technical issues and develop a consensus approach to analysis of plasma cells. The primary clinical applications identified were: differential diagnosis of neoplastic plasma cell disorders from reactive plasmacytosis; identifying risk of progression in patients with MGUS and detecting minimal residual disease. A range of technical recommendations were identified, including: 1) CD38, CD138 and CD45 should all be included in at least one tube for plasma cell identification and enumeration. The primary gate should be based on CD38 vs. CD138 expression; 2) after treatment, clonality assessment is only likely to be informative when combined with immunophenotype to detect abnormal cells. Flow cytometry is suitable for demonstrating a stringent complete remission; 3) for detection of abnormal plasma cells, a minimal panel should include CD19 and CD56. A preferred panel would also include CD20, CD117, CD28 and CD27; 4) discrepancies between the percentage of plasma cells detected by flow cytometry and morphology are primarily related to sample quality and it is, therefore, important to determine that marrow elements are present in follow-up samples, particularly normal plasma cells in MRD negative cases.

Generation of B and plasma cells involves several organs with a necessary cell trafficking between them. A detailed phenotypic characterization of four circulating B-cell subsets (immature-, naïve-, memory-B-lymphocytes and plasma cells) of 106 healthy adults was realized by multiparametric flow cytometry. We show that CD10, CD27 and CD38 is the minimal combination of subsetting markers allowing unequivocal identification of immature (CD10 IntroductionHuman B-cell biology has been extensively documented. CD38-memory B cells. Very low numbers of plasma cells (2/mL) are found in peripheral blood of healthy donors. Because of their low count, only few studies have been devoted to characterizing their phenotype, most of them dealing with newly generated plasma cells after in vivo immunization.2 Steady-state circulating plasma cells lack CD20, express CD19 and CD38 high . It has been recently reported that steady-state circulating plasma cells are mainly of mucosal origin, the majority of them secreting IgA (84%), expressing CCR10 (56%) and β7 integrin (32%).3 Steady-state circulating plasma cells are generally termed plasmablasts because only half express CD138, a proteoglycan that is a hallmark of plasma cells, 4 while they are CD45 + and HLA-class II + . Plasmablasts are generated in the lymph nodes, and induced to circulate for a short period until they will reach a niche in bone marrow, spleen, mucosa associated lymphoid tissues (MALT) or lymph nodes.5 These niches will provide circulating early plasma cells with those factors required to survive and to further differentiate into long-living mature plasma cells.1 In murine bone marrow, plasma cell niche involves SDF-1 producing cells and is shared with hematopoietic stem cells

Genetic studies revealed that SHIP1 limits blood cell production and immune regulatory cell numbers in vivo. We postulated that molecular targeting of SHIP1 might enhance blood cell production and increase immunoregulatory capacity. In this study, we report the identification of a chemical inhibitor of SHIP1, 3 α-aminocholestane (3AC). Treatment with 3AC significantly expands the myeloid immunoregulatory cell compartment and impairs the ability of peripheral lymphoid tissues to prime allogeneic T cell responses. In addition, 3AC treatment profoundly increases granulocyte production without triggering the myeloid-associated lung consolidation observed in SHIP1−/− mice. Moreover, 3AC also enhances RBC, neutrophil, and platelet recovery in myelosuppressed hosts. Intriguingly, we also find that chemical inhibition of SHIP1 triggers apoptosis of blood cancer cells. Thus, SHIP1 inhibitors represent a novel class of small molecules that have the potential to enhance allogeneic transplantation, boost blood cell production, and improve the treatment of hematologic malignancies.