This study introduces an in-depth flow cytometric method for the analysis of nucleated erythroid progenitors during bone marrow regeneration. Initial immunophenotypic analysis with the conventional erythroid-associated markers CD36, CD71 and CD235a was supplemented with the analysis of additional markers, including CD105, CD117, CD45, CD38 and cell-scattered light characteristics. Our data show that the expression of CD105 and CD117 is critical for the distinction between four phenotypically different developmental stages of nucleated erythroid progenitors: pro-erythroblasts, basophilic erythroblasts, polychromatophilic erythroblasts and orthochromatophilic erythroblasts. CD105 antigen expression was specifically associated with pro-erythroblasts and basophilic erythroblasts, whereas CD117 was expressed at the earliest pro-erythroblast stage. Both antigens were progressively lost throughout the course of differentiation. These data allow for the identification of aberrant erythroid development in acute erythroid leukemia or myelodysplastic syndrome.

B-cell chronic lymphocytic leukemia (B-CLL) represents a heterogeneous disease with a very variable outcome. The reliable prognosis of this disease at the time of initial diagnosis is difficult to predict. The purpose of this preliminary study was to utilize the nucleolar morphology and to investigate the incidence of main nucleolar types in leukemic lymphocytes in B-CLL patients to assess their possible predictive value for the disease outcome, in correlation with immunophenotype parameters. The evaluation of nucleolar morphology of pathologic lymphocytes was performed at diagnosis and during the course of disease. Median follow up period of patients was 16.4 months (range from 2 to 32 months) from diagnosis. The nucleoli were visualized by a simple cytochemical demonstration of RNA and the proportion of main nucleolar types in pathologic lymphocyte population infiltrating bone marrow of 84 patients suffering from B-CLL was analyzed. The presence of ring shaped and compact nucleoli in leukemic lymphocytes divided patients into two subgroups with different outcome of the disease. Malignant lymphocytes of the majority of patients (Group 1, 71 patients, 84.5%) mostly contained ring shaped nucleoli. These patients were in stable phase and did not require any treatment during the follow up. The population of leukemic cells of a small group of B-CLL patients (Group 2, 13 patients, 15.4%) was characterized by the presence of various proportions of pathologic lymphocytes with one large compact nucleolus.Different response to the therapy discriminated the B-CLL patients whose leukemic lymphocytes revealed evident compact nucleoli at presentation, to next two subsets. Four of these patients (Group 2, 4/13, 31%) appeared to be resistant to chemotherapy, others (9/13, 69%) showed response to therapy, though the response time was variable. Leukemic cells with compact nucleolus morphologically resembled prolymphocytes, but hematologically and immunophenotypically did not fulfill the diagnostic criteria for prolymphocyte population. None of our B-CLL patients had the signs of transformation to prolymphocytic or other type of B cell neoplasms during the follow up. Our results indicate the possibility of relationship between the presence of malignant lymphocytes with compact nucleoli and unfavorable outcome in patients with B-CLL. The simplicity and utility of the nucleolar test as a possible prognostic parameter may help to identify the subset of patients with early B-CLL disease that will run a more progressive course.

In this review, we discuss methodological principles and clinical applications of minimal residual disease (MRD) assays based on multiparameter flow cytometry (MFC). The introduction of methods for MRD detection has revolutionized monitoring of treatment response in acute leukemia. Great progress has been made in the development of wide array of flow cytometric techniques for rare event detection. This advance was accompanied by increasingly greater understanding of the immunophenotypic features of leukemic and normal lymphoid cells, and of the antigenic differences that make MRD studies possible. Immunologic testing of MRD relies on "leukemia-associated" immunophenotypes which can be identified by MFC in the most of acute leukemia cases. The recent technical innovations in routine MFC (3 lasers and≥8 colors) and the new developments in software for data analysis make this technology the most attractive for MRD diagnostics. The importance of MFC methodology will be further strengthened by the ongoing international standardization efforts. Results of MRD testing provide unique and clinically important information. The systematic application of immunologic techniques to study MRD in clinical samples has demonstrated the prognostic significance of MRD in patients, leading to the use of MRD to regulate treatment intensity in many contemporary protocols. The identification of new markers of MRD should increase the sensitivity of MRD testing by MFC and is required to widen the applicability of MRD studies.

Multiple myeloma (MM) is an incurable heterogeneous hematological malignancy in which relapse is characterized by re-growth of residual tumor and immune suppression with a complex biology that affects many aspects of the disease and its response to treatment. The bone marrow microenvironment, including immune cells, plays a central role in MM pathogenesis, survival, and drug resistance. The advances in basic and translational research, introduction of novel agents, particularly combination therapies, improved indicators of quality of life and survival. Minimal residual disease (MRD) detection by multiparameter flow cytometry (MFC) has revolutionized monitoring of treatment response in MM. The importance of MFC methodology will be further strengthened by the ongoing international standardization efforts. Results of MRD testing provide unique and clinically important information and demonstrated the prognostic significance of MRD in patients, leading to regulate treatment intensity in many contemporary protocols. In this review, we will summarize the principal approaches in MM immunotherapy, focusing how new agents have potential in the treatment of MM and application of MRD detection by MFC as a surrogate endpoint would allow quicker evaluation of treatment outcomes and rapid identification of effective new therapies.