Report of the European Myeloma Network on multiparametric flow cytometry in multiple myeloma and related disorders.

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.

High-density oligonucleotide array analysis reveals extensive differences between freshly isolated blood and hepatic natural killer cells.

Hepatic NK cells are more cytotoxic than blood NK cells against tumor cells. To understand the basis of this difference in cytotoxicity we analyzed RNA derived from freshly isolated rat blood and hepatic NK cells [high-density (HD) and low-density subpopulations] by high-density oligonucleotide arrays (Affymetrix), containing about 9,000 genes and expressed sequence tags. IL-2-treated blood NK (A-NK) cells and IL-2-treated hepatic HD cells were used as a reference of NK cell activation. About 150 genes and expressed sequence tags were differentially expressed between hepatic and blood NK cells. Surprisingly, more than half of the increased expressed genes in hepatic NK cells were not increased in A-NK cells. Differentially expressed genes like the stem cell factor receptor c-kit and the chemokine receptor CCR5 can contribute to the homing and differentiation of hepatic NK cells in the liver sinusoids. Several of the differentially expressed genes can possibly contribute to the enhanced cytotoxic activity of hepatic NK cells: cell membrane receptors like NKG2D, NKG2C, CD94, ecto-ATPase; signaling molecules like phosphatidylinositol 3-kinase; granule-associated effector molecules like granzymes and defensin NP3. Moreover, it appears that redirection of cytotoxic granules and increase in intracellular Ca2+ are convergence points of several of these genes.