Marta Siviero

The chemokine receptor CXCR3 is expressed on malignant B cells and mediates chemotaxis

B- and T-cell recirculation is crucial for the function of the immune system, with the control of cell migration being mainly mediated by several chemokines and their receptors. In this study, we investigated the expression and function of CXCR3 on normal and malignant B cells from 65 patients with chronic lymphoproliferative disorders (CLDs). Although CXCR3 is lacking on CD5(+) and CD5(-) B cells from healthy subjects, it is expressed on leukemic B lymphocytes from all (31/31) patients with chronic lymphocytic leukemia (CLL). The presence of CXCR3 was heterogeneous in other B-cell disorders, being expressed in 2 of 7 patients with mantle cell lymphoma (MCL), 4 of 12 patients with hairy cell leukemia (HCL), and 11 of 15 patients with other subtypes of non-Hodgkins lymphomas (NHLs). Chemotaxis assay shows that normal B cells from healthy subjects do not migrate in response to IFN-inducible protein 10 (IP-10) and IFN-gamma-induced monokine (Mig). In contrast, a definite migration in response to IP-10 and Mig has been observed in all malignant B cells from patients with CLL, but not in patients with HCL or MCL (1/7 cases tested). Neoplastic B cells from other NHLs showed a heterogenous pattern. The migration elicited by IP-10 and Mig was inhibited by blocking CXCR3. No effect of IP-10 and Mig chemokines was observed on the cytosolic calcium concentration in malignant B cells. The data reported here demonstrate that CXCR3 is expressed on malignant B cells from CLDs, particularly in patients with CLL, and represents a fully functional receptor involved in chemotaxis of malignant B lymphocytes.

Modulation of immune response by the acute and chronic exposure to high altitude

PURPOSE The chronic exposure at high altitude (HA) represents an ideal model for evaluating the in vivo effects of hypobaric hypoxia. Taking advantage of the EV-K2-CNR Pyramid, this study was designed to evaluate whether acute and chronic hypoxia differently modulates the in vivo immune responses. METHODS The study includes 13 healthy female moderately active volunteers participating to the Italian HA project EV-K2-CNR. Peripheral blood lymphocytes, collected at sea level and at HA in the Pyramid Laboratory of CNR, Nepal (5050 m), were immunologically characterized by flow cytometry and a series of molecular and functional analyses. RESULTS Flow cytometric analyses showed that: a) CD3+ T lymphocytes significantly decreased during both acute and chronic exposure to HA, b) T-cell fall was totally due to CD4+ T-cell reduction, c) B lymphocytes were not influenced by the exposure to HA, and d) natural killer (NK) cells significantly increased during acute and chronic exposure. The evaluation of the Th1/Th2 pattern demonstrated a significant decrease of the expression of the Th1 cytokine interferon-gamma (IFN-gamma) by circulating T cells during acute and chronic exposure to HA. The expression by T cells of CXCR3, a chemokine receptor typically expressed by Th1/Tc1 cells, paralleled the decrease of IFN-gamma. On the contrary, the expression of IL-4 was not conditioned by the exposure to HA. Finally, functional studies showed a significant reduction of the proliferative activity in response to mitogen (PHA) both in acute and chronic HA exposure. Despite the increased number of NK cells, NK cytotoxic activity was not influenced by the HA exposure. CONCLUSIONS Our results indicate that the in vivo exposure to HA leads to an impairment of the homeostatic regulation of Th1/Th2 immune balance that potentially could favor long-term immunological alterations and increase the risk of infections.

Regulation of alveolar macrophage-T cell interactions during Th1-type sarcoid inflammatory process

The accessory function of antigen-presenting cells depends on the presence of a number of costimulatory molecules, including members of the B7 family (CD80 and CD86) and the CD5 coligand CD72. The aim of this study was to evaluate the regulation of T cell-antigen-presenting cell costimulatory pathways in the lung of patients with a typical Th1-type reaction, i.e., sarcoidosis. Although normal alveolar macrophages (AMs) did not bear or bore low levels of costimulatory molecules, AMs from sarcoid patients with CD4 T-cell alveolitis upmodulated CD80, CD86, and CD72 and expressed high levels of interleukin (IL)-15; lymphocytes accounting for T-cell alveolitis expressed Th1-type cytokines [interferon (IFN)-γ and/or IL-2] and bore high levels of CD5 and CD28 but not of CD152 molecules. In vitro stimulation of AMs with Th1-related cytokines (IL-15 and IFN-γ) upregulated the expression of CD80 and CD86 molecules. However, stimulation with IL-15 induced the expression of Th1-type cytokines (IFN-γ) and CD28 on sarcoid T cells, suggesting a role for this macrophage-derived cytokine in the activation of the sarcoid T-cell pool. The hypothesis that CD80 and CD86 molecules regulate the sarcoid T-cell response was confirmed by the evidence that AMs induced a strong proliferation of T cells that was inhibited by pretreatment with CD80 and CD86 monoclonal antibodies. To account for these data, it is proposed that locally released cytokines provide AMs with accessory properties that contribute to the development of sarcoid T-cell alveolitis.

Immune effector cells in idiopathic pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a poorly understood immunomediated disorder that is characterized by three major features; influx of inflammatory cells into the lower respiratory tract, alveolar epithelial or capillary cell injury, and release of cytokines that stimulate proliferation of fibroblasts and type II pneumocytes along with deposition of extracellular matrix proteins, notably collagen. In the past few years interest in the pathogenetic mechanisms taking place in IPF has focused on immune effector cells that are involved in pulmonary inflammatory pathways, cell-specific injury, and fibroblast activation. In particular, accumulating evidence indicates that a complex relationship exists between the macrophage/lymphocyte/neutrophil cellular axis and the local network of cytokines that, through paracrine and autocrine interactions, coordinate inflammation and fibrogenesis in the respiratory tract.

B7 costimulatory molecules from malignant cells in patients with B-cell chronic lymphoproliferative disorders trigger T-cell proliferation

B7 family molecules are involved in T–B‐cell communications after interaction with their ligands CD28 and CD152. They play a key role in costimulatory mechanisms and during antigen presentation by efficient antigen presenting cells. B7 molecules are usually absent or expressed at low intensity on B lymphocytes from healthy subjects. In this study, the authors addressed the questions of whether B7 molecules are expressed and modulated in vitro on malignant B lymphocytes from patients with chronic lymphoproliferative diseases of B‐cell type and whether they are able to trigger allogenic T‐cell reactions.