CD45RO+ T-cells immunoregulate spontaneous in vitro immunoglobulin production by normal and chronic lymphocytic leukaemia B-cells

Differential Expression of CD45RO and CD45RA in Bovine T Cells

Effective vaccination induces immune memory to protect animals upon pathogen re-encounter. Despite contradictory reports, bovine memory T cells are identified based on two isoforms of CD45, expression of CD45RO plus exclusion of CD45RA. In this report, we contrasted CD45RA/RO expression on circulatory T cells with IFNγ and IL4 expression induced by a conventional method. To our surprise, 20% of cattle from an enclosed herd did not express CD45RO on T cells without any significant difference on CD45RA expression and IFNγ or IL4 induction. In CD45RO expressing cattle, CD45RA and CD45RO expressions excluded each other, with dominant CD45RO (>90%) expression on gamma delta (γδ) followed by CD4+ (60%) but significantly higher CD45RA expression on CD8+ T cells (about 80%). Importantly, more than 80% of CD45RO expressing CD4+ and CD8+ T cells failed to produce IFNγ and IL-4; however, within the cytokine inducing cells, CD4+ T cells highly expressed CD45RO but those within CD8+ T cells mostly expressed CD45RA. Hence, CD45RO is not ubiquitously expressed in cattle, and rather than with memory phenotype, CD45RA/RO expression are more associated with distinct T cell subtypes.

Molecular and cellular mechanisms of CLL: novel therapeutic approaches

The mainstay of therapy of chronic lymphocytic leukemia (CLL) is cytotoxic chemotherapy; however, CLL is still an incurable disease with resistance to therapy developing in the majority of patients. In recent years, our understanding of the biological basis of CLL pathogenesis has substantially improved and novel treatment strategies are emerging. Tailoring and individualizing therapy according to the molecular and cellular biology of the disease is on the horizon, and advances with targeted agents such as monoclonal antibodies combined with traditional chemotherapy have lead to improved remission rates. The proposed key role of the B-cell receptor (BCR) in CLL pathogenesis has led to a number of possible opportunities for therapeutic exploitation. We are beginning to understand that the microenvironment is of utmost importance in CLL because certain T-cell subsets and stromal cells support the outgrowth and development of the malignant clone. Furthermore, an increase in our understanding of the deregulated cell-death machinery in CLL is a prerequisite to developing new targeted strategies that might be more effective in engaging with the cell-death machinery. This Review summarizes the progress made in understanding these features of CLL biology and describes novel treatment strategies that have also been exploited in current clinical trials.

Prolegomenon for Chronic Lymphocytic Leukaemia

Chronic lymphocytic leukaemia (CLL) is a unique lymphoproliferative disorder that scarcely occurs under the age of 40; thereafter the incidence of CLL increases exponentially with age. CLL is characterized by progressive expansion of malignant CD5+ME+ B-cell clone accompanied by a myriad of cellular and humoral immune defects. Each of them might be linked to different clinically manifested complications such as increasing rate of infections, autoimmune disorders and disturbed immune surveillance against tumour cells. We assume that CLL occurs as a consequence of age-dependent, genetically related functional restrictions of the thymic microenvironment in supporting common lymphoid progenitor cells (CD5+ME+CD4-CD8-) to differentiate into mature T-cell and B-cell descendants. In conjunction with genetic abnormalities developing in B-cell progenitors, presumably expressing P glycoprotein (Pgp+), we postulate that developmentally altered T-cell descendants, along with quantitative imbalance among CD4+, their subsets and CD8+ lymphocytes in the peripheral blood, play an important additional role in facilitating the malignant B-cell clone emergence and in modulating the CLL clinical evolution. Namely, imbalance of any of T-cell-mediated cell interactive homeostatic mechanisms accompanied by imbalance in the production of various cytokines might in CLL influence leukaemic B-cell growth by deregulating inducer (c-myc and p53) and/or suppressor (bcl-2 and mutant p53) oncogenes responsible for the promotion or suppression of B-cell mitogenesis that may in turn further contribute to their impaired differentiation and/or differentiation arrest. In conclusion, CLL might be interpreted as a primary immunodeficiency syndrome developing in elderly population due to gradually evolving restriction of genetically controlled programs in the thymic microenvironment responsible for irregular maturation of common lymphoid progenitor cells that constitutively express CD5 antigen and ME receptor into T-cell and B-cell descendants.

Analysis of T Cells in Paroxysmal Nocturnal Hemoglobinuria Provides Direct Evidence That Thymic T-Cell Production Declines With Age

Peripheral blood T cells in patients with paroxysmal nocturnal hemoglobinuria (PNH) comprise a mixture of residual normal and glycosylphosphatidylinositol (GPI)-deficient PNH cells. Using multicolor flow cytometry, we demonstrated significant differences between the proportions of naive and memory cells within these populations. PNH T cells comprise mainly naive cells (CD45RA+CD45R0−), whereas normal T cells in the same patients were predominantly memory (CD45RA−CD45R0+) cells. Functional analyses showed that GPI-deficient CD45RA+ T cells can convert to a CD45R0+ phenotype. We present data from a PNH patient in remission for 20 years who still had significant numbers of GPI-deficient T cells; these showed a normal distribution of naive and memory components. The predominantly naive phenotype of GPI-deficient T cells seen in PNH patients with active disease likely reflects the phenotype of recent normal thymic emigrants. In patients where hematopoiesis was predominantly derived from the PNH stem cell, absolute numbers of both naive PNH CD4+ cells and CD8+ cells show an inverse correlation with patient age, implying this age-related decline in T-cell production is secondary to a decrease in thymic activity rather than a stem cell defect.

Decision-tree approach to the immunophenotype-based prognosis of the B-cell chronic lymphocytic leukemia

Use of a nonlinear prediction method, such as machine learning, is a valuable choice in predicting progression rate of disease when applied to the highly variable and correlated biological data such as those in patients with chronic lymphocytic leukemia (CLL). In this work, decision-tree approach to cell phenotype-based prognosis of CLL was adopted. The panel of 33 (32 different phenotypic features and serum concentration of sCD23) parameters was simultaneously presented to the C4.5 decision tree which extracted the most informative of them and subsequently performed classification of CLL patients against the modified Rai staging system. It has been shown that substantial correlation between the percentage of expression of the CD23 molecule on CD19+ B-cells, the level of sCD23, the percentage of CD45RA+, and the absolute number of CD4CD45RA+RO+ T-cells and the clinical stages, exists. The prediction vector, composed of their concatenated values, was able to correctly associate 83% of the cases in the low-risk group (Rai stage 0), 100% of the cases in the intermediate-risk group (Rai stage I and II), and 89% of the cases in the high-risk group (Rai stage III and IV) of CLL patients. Predictivity of this vector was 100%, 95%, and 89%, respectively. In conclusion, from the described analysis, it may be inferred that two processes play important roles in the progression rate of CLL: 1.deregulated function of the CD23 gene in B-cells accompanied by the appearance of its cleaved product sCD23 in the sera; and 2. functionally impaired and imbalanced CD4 T-cell subpopulations found in the peripheral blood of CLL patients.