Lymphoid Hematopoiesis and Lymphocytes Differentiation and Maturation

Lymphocytes belong to the lymphoid lineage and are considered as divergent from other blood cells lineages as those from the myeloid or erythroid lineage. Lymphoid hematopoiesis is not trivial, because although lymphocytes are found in the bloodstream and their precursor originates in the bone marrow, they mainly belong to the separate lymphatic system, which interacts with the blood circulation. We will discuss B cell differentiation in the bone marrow and the later stages of maturation in secondary lymphoid tissues, besides the B cell profiles in interfollicular, perifollicular, and follicular areas. In addition, we will also discuss T-cell precursor and natural killer cells derivation in the marrow. Furthermore, we will also discuss T-cell precursor migration to thymus, differentiation, rearrangement, thymic selection, involved transcription factors, and, finally, T-cell profiles and subsets in secondary lymphoid organs. We will provide flow cytometry plots showing strategies to identify and characterize NK, T and B lymphocytes and their subsets in circulation. Furthermore, we will provide illustrations to help the reader to understand and visualize the information provide over the chapter. Furthermore, the comprehension about lymphocytes and their contribution to the immune response will favor their application in developmental hematology and immunology. These topics are very important for the continuous development of knowledge

Study of naive and memory T cells distribution in hematological malignancies.

Células T de memória são a marca registrada da imunidade adaptativa, e podem ser caracterizadas em central memory (TCM) e effector memory (TEM) T cells. A participação destas células no curso de doenças hematológicas é descrita como mecanismo relacionado à evolução das mesmas. Neste trabalho, analisamos o sangue periférico de doadores de sangue e pacientes com Mielodisplasia (SMD), Mieloma Múltiplo (MM) e Leucemia linfocítica crônica B (LLC), e avaliamos a distribuição das células T CD4+ e CD8+ naive e de memória. SMD e MM não apresentaram resultados significativos, mas na LLC, as células T CD4+ estavam alteradas e dependentes do prognóstico, com aumento das células TCM somente nos pacientes com prognóstico ruim. Essas evidências sugerem que interações imunológicas entre células B da LLC e células T CD4+ possa ser um mecanismo próprio da doença que venha interferir na fisiopatologia e favorecer a geração de células TCM, que podem fornecer sinais de sobrevivência, como citocinas e CD40L, contribuindo assim para o estabelecimento e agressividade da LLC.Memory T cells are the hallmark of adaptive immunity and are characterized as central (TCM) and effector memory (TEM) T cells. The influence of T cells in the course of hematological malignancies has been described as a mechanism related to the evolution. In this study, we analyzed the peripheral blood of healthy donors and patients with myelodysplastic syndrome (MDS), multiple myeloma (MM) and chronic lymphocytic leukemia B (CLL), and analyzed the distribution of CD4+ and CD8+ naive and memory T cells. MDS and MM revealed no significant difference, but CLL patients showed changes in CD4+ T cell and it were dependent on the prognosis. Patients with poor prognosis presented increased in frequency and absolute number of TCM cells. These evidences show that immunological interactions between CLL and CD4+ T cells could be a disease mechanism that could interfere in pathophysiology and result in the generation of TCM cells, that provide survival signals to the tumor clone, such as cytokines and CD40L, thus contributing to establishment and more aggressive CLL progression

Involvement of memory T-cells in the pathophysiology of chronic lymphocytic leukemia

The role of T-cells in the pathogenesis of chronic lymphocytic leukemia has recently gained much attention due to the importance of the constant interaction between neoplastic B-cells with microenvironment substratum and T-cells. It is believed that these interactions modulate the clinical course of the disease, mainly through the regulation of the expansion, differentiation, and survival of chronic lymphocytic leukemia B-cells. Importantly, this crosstalk may also change the number, function, and memory phenotype of normal T-cells, thereby altering the amplitude and/or efficiency of adaptive immunity in chronic lymphocytic leukemia patients. The present study presents an overview on important aspects of this immunological crosstalk, particularly on the abnormalities of chronic lymphocytic leukemia B-cells and the alterations in normal T-cells, with focus on the CD4 memory T-cell compartment that could offer survival signals to chronic lymphocytic leukemia B-cell clone(s) and contribute to the establishment and progression of the disease. The authors believe that understanding the biological consequences of the interaction between normal T- and neoplastic B-cells in chronic lymphocytic leukemia may allow for improvements in the prognostic information and therapeutic approaches for this disease

ZAP-70 expression is associated with increased CD4 central memory T cells in chronic lymphocytic leukemia: cross-sectional study

Background: Although chronic lymphocytic leukemia is basically a B cell disease, its pathophysiology and evolution are thought to be significantly influenced by T cells, as these are probably the most important interaction partner of neoplastic B cells, participating in their expansion, differentiation and survival. Chronic lymphocytic leukemia B cells may also drive functional and phenotypic changes of non-malignant T cells. There are few data about the association between memory T cells and prognosis, especially related to ZAP-70, a common reliable surrogate of the gold standard chronic lymphocytic leukemia prognostic markers. Objective: The aim of this study was to investigate whether the expression of ZAP-70 in chronic lymphocytic leukemia patients is associated with abnormal patterns of the distribution of naïve and memory T cells related to crosstalk between these cells. Methods: In this cross-sectional, controlled study, patients with chronic lymphocytic leukemia were compared with healthy blood donors regarding the expression of ZAP-70 and the distribution of naïve and memory T cell subsets in peripheral blood as measured by flow cytometry. Results: ZAP-70 positive patients presented an increased frequency and absolute number of central memory CD4+ T cells, but not CD8+ T cells, compared to ZAP-70 negative patients and age-matched apparently healthy donors. Conclusions: Because central memory CD4+ T cells are located in lymph nodes and express CD40L, we consider that malignant ZAP-70-positive B cells may receive beneficial signals from central memory CD4+ T cells as they accumulate, which could contribute to more aggressive disease. Keywords: Chronic lymphocytic leukemia, ZAP-70 protein-tyrosine kinase, Memory T cell

Detection of Central Nervous System Infiltration by Myeloid and Lymphoid Hematologic Neoplasms Using Flow Cytometry Analysis: Diagnostic Accuracy Study

IntroductionInfiltration of the central nervous system (CNS) by hematologic or lymphoid malignant cells can cause extensive neurological damage, be progressive and fatal. However, usually, the cerebrospinal fluid (CSF) has low cellularity and rapid cell degeneration, which can impair cytometry analysis. Storage and transport measures, sample preparation, and staining protocols can interfere with diagnostic accuracy.ObjectiveTo calculate the diagnostic performance of flow cytometry (FC) using a cell stabilizer for sample preservation compared to cytomorphology in the detection of CNS infiltration by lymphoid and hematologic neoplasms.MethodsCell samples from all consecutive patients with suspected infiltration by hematological malignancies evaluated between January 2014 and December 2016 were included. Cases were analyzed by FC using a cell preservation medium and cytomorphology. Sensitivity and specificity were calculated.ResultsFrom 414 CSF samples, 72 had a phenotype compatible with characteristics of infiltration by hematological disease, whereas cytology was positive for 35 cases. FC showed higher sensitivity and specificity when compared to cytomorphology, particularly in cases with cellularity under 5 leukocytes/mm3.ConclusionWe demonstrated that collecting CSF in a medium that preserves the stability of the sample improves accuracy when compared to cytomorphology, particularly in low-volume and low-cellularity samples