Anna Corcione

Interleukin-31 and thymic stromal lymphopoietin expression in plasma and lymph node from Hodgkin lymphoma patients Interleukin-31 and thymic stromal lymphopoietin expression in plasma and lymph node from Hodgkin lymphoma patients

CX₃CL1, or fractalkine, the unique member of the CX₃C chemokine family, exists as a transmembrane glycoprotein, as well as in soluble form, each mediating different biological activities, and is constitutively expressed in many hematopoietic and nonhematopoietic tissues. CX₃CR1, the CX₃CL1 exclusive receptor, is a classical GPCR, expressed on NK cells, CD14⁺ monocytes, and some subpopulation of T cells, B cells, and mast cells. A recent paper by our group has demonstrated for the first time that highly purified human B cells from tonsil and peripheral blood expressed CX₃CR1 at mRNA and protein levels. In particular, tonsil naïve, GC, and memory B cells expressed CX₃CR1, but only GC centrocytes were attracted by soluble CX₃CL1, which with its receptor, are also involved in the pathogenesis of several inflammatory disorders, as well as of cancer. Previous studies have shown that CX₃CR1 is up-regulated in different types of B cell lymphoma, as well as in B-CLL. Recently, we have demonstrated that the CX₃CL1/CX₃CR1 axis is involved in the interaction of B-CLL cells with their microenvironment. Taken together, our data delineate a novel role for the CX₃CL1/CX₃CR1 complex in the biology of normal B cells and B-CLL cells. These topics are the subject of this review article.

Fractalkine/CX₃CL1, a surface chemokine, binds to CX₃CR1 expressed by different lymphocyte subsets. Since CX₃CL1 has been detected in the germinal centres of secondary lymphoid tissue, in this study we have investigated CX₃CR1 expression and function in human naïve, germinal centre and memory B cells isolated from tonsil or peripheral blood. We demonstrate unambiguously that highly purified human B cells from tonsil and peripheral blood expressed CX₃CR1 at mRNA and protein levels as assessed by quantitative PCR, flow cytometry and competition binding assays. In particular, naïve, germinal centre and memory B cells expressed CX₃CR1 but only germinal centre B cells were attracted by soluble CX₃CL1 in a transwell assay. CX₃CL1 signalling in germinal centre B cells involved PI3K, Erk1/2, p38, and Src phosphorylation, as assessed by Western blot experiments. CX₃CR1⁺ germinal centre B cells were devoid of centroblasts and enriched for centrocytes that migrated to soluble CX₃CL1. ELISA assay showed that soluble CX₃CL1 was secreted constitutively by follicular dendritic cells and T follicular helper cells, two cell populations homing in the germinal centre light zone as centrocytes. At variance with that observed in humans, soluble CX₃CL1 did not attract spleen B cells from wild type mice. OVA immunized CX₃CR1⁻/⁻ or CX₃CL1⁻/⁻ mice showed significantly decreased specific IgG production compared to wild type mice. We propose a model whereby human follicular dendritic cells and T follicular helper cells release in the light zone of germinal centre soluble CX₃CL1 that attracts centrocytes. The functional implications of these results warrant further investigation.

Introduction: In chronic inflammatory disorders, B cells can contribute to tissue damage by autoantibody production and antigen presentation to T cells. Here, we have characterized synovial fluid and tissue B-cell subsets in patients with oligoarticular juvenile idiopathic arthritis (JIA), an issue not addressed before in detail. Methods: B cells from synovial fluid (SF) and peripheral blood (PB) of 25 JIA patients, as well as from PB of 20 controls of comparable age, were characterized by multicolor flow cytometry. Immunoglobulin-secreting cells were detected by ELISPOT. Immunohistochemical analyses of synovial tissue from three JIA patients were performed. Results: JIA SF B cells were enriched in CD27⁺ and CD27^- switch memory B cells, but not in CD27⁺ IgM memory B cells, compared with patient and control PB. Plasma blasts were more abundant in SF and secreted higher amounts of IgG. Lymphoid aggregates not organized in follicle-like structures were detected in synovial tissue sections and were surrounded by CD138⁺ plasma cells. Finally, transitional B cells were significantly increased in JIA PB versus SF or control PB. CCR5, CCR8, CXCR2, and CXCR3 were upregulated, whereas CCR6, CCR7, and CXCR5 were downregulated on SF CD27⁺ and CD27^- switch memory B cells compared with their circulating counterparts. SF CD27⁺ and CD27^- switch memory B cells expressed at high levels the costimulatory molecule CD86 and the activation marker CD69. Conclusions: This study demonstrates for the first time an expansion of activated switch memory B cells and of IgG-secreting plasma blasts in the SF from oligoarticular JIA patients. Memory B cells belonged to either the CD27⁺or the CD27^- subsets and expressed CD86, suggesting their involvement in antigen presentation to T cells. Patterns of chemokines-receptor expression on CD27⁺ and CD27^- switch memory B cells delineated potential mechanisms for their recruitment to the inflamed joints.

Human mesenchymal stem cells (hMSCs) suppress T-cell and dendritic-cell function and represent a promising strategy for cell therapy of autoimmune diseases. Nevertheless, no information is currently available on the effects of hMSCs on B cells, which may have a large impact on the clinical use of these cells. hMSCs isolated from the bone marrow and B cells purified from the peripheral blood of healthy donors were cocultured with different B-cell tropic stimuli. B-cell proliferation was inhibited by hMSCs through an arrest in the G₀/G₁ phase of the cell cycle and not through the induction of apoptosis. A major mechanism of B-cell suppression was hMSC production of soluble factors, as indicated by transwell experiments. hMSCs inhibited B-cell differentiation because IgM, IgG, and IgA production was significantly impaired. CXCR4, CXCR5, and CCR7 B-cell expression, as well as chemotaxis to CXCL12, the CXCR4 ligand, and CXCL13, the CXCR5 ligand, were significantly down-regulated by hMSCs, suggesting that these cells affect chemotactic properties of B cells. B-cell costimulatory molecule expression and cytokine production were unaffected by hMSCs. These results further support the potential therapeutic use of hMSCs in immune-mediated disorders, including those in which B cells play a major role.

Clonally expanded populations of B cells carrying somatic mutations of Ig variable (V) region genes have been detected in the CNS of subjects with multiple sclerosis (MS), suggesting that a process of B cell affinity maturation with ensuing production of potentially pathogenic autoantibodies may occur inside the CNS. Here, we have characterized the B cell subsets present in the cerebrospinal fluid (CSF) of MS patients and of individuals with other inflammatory neurological disorders by flow cytometry. CD19⁺CD38^high+CD77⁺, Ki67⁺, Bcl-2^–centroblasts, i.e., a B cell subset found exclusively in secondary lymphoid organs, were detected in the CSF but not in paired peripheral blood from both patient groups. CD27⁺IgD^–memory B cells, i.e., cells with hyper-mutated IgV genes, were significantly increased in the CSF vs. paired peripheral blood and displayed up-regulation of the CD80 and CD86 costimulatory molecules and of CC chemokine receptor (CCR) 1, CCR2, and CCR4 in both patient groups. Lymphotoxin-α, CXC ligand (CXCL) 12, and CXCL13, key mediators of lymphoid neogenesis, were present in the CSF from patients with MS and other inflammatory neurological disorders and were expressed in MS brain tissue, with selective localization in the outer layer of the capillary vessel wall. In conclusion, this study suggests that a compartmentalized B cell response occurs within the CNS during an ongoing inflammatory reaction, through a recapitulation of all stages of B cell differentiation observed in secondary lymphoid organs. The presence of lymphotoxin-α, CXCL12, and CXCL13 in the CNS may provide favorable microenvironmental conditions for these events.

Purpose: Few data are available in the literature on chemokine receptor expression and migratory capability of mantle cell lymphoma (MCL) B cells. Information on these issues may allow us to identify novel mechanisms of chemokine-driven tumor cell migration.Experimental Design: The research was designed to investigate: (a) expression of CCR1 to CCR7 and CXCR1 to CXCR5 chemokine receptors; and (b) chemotaxis to the respective ligands in MCL B cells and in their normal counterparts, i.e., CD5+ B cells.Results: Malignant B cells from MCL patients and normal counterparts displayed similar chemokine receptor profiles. MCL B cells were induced to migrate by CXCL12 and CCL19, whereas normal CD5+ B cells migrated to the former, but not the latter chemokine. Overnight culture of MCL B cells and their normal counterparts with CXCL12 cross-sensitized other chemokine receptors to their ligands in some tumor samples but not in CD5+ B cells.Conclusions: CCR7 and CXCR4 ligands may play a key role in tumor cell migration and spreading in vivo. CXCL12 may additionally contribute by sensitizing MCL B cells to respond to the ligands of other chemokine receptors.

We have investigated the effects of nine CC chemokines, i.e. macrophage inflammatory protein (MIP)‐1α/CCL3, MIP‐1β/CCL4, MIP‐3α/CCL20, MIP‐5/CCL15, monocyte chemotactic protein (MCP)‐1/CCL2, MCP‐2/CCL8, MCP‐3/CCL7, eotaxin/CCL11 and macrophage‐derived chemokine (MDC)/CCL22 on the locomotion of human tonsil B lymphocytes and their subsets. Upon isolation, B cells were poorly responsive, but, following short‐term culture, they displayed statistically significant chemotactic responses (P < 0.001) to MIP‐1α, MIP‐5, MCP‐1, MCP‐2, MCP‐3 and MDC. CC chemokine receptor (CCR) 1 to CCR6 were up‐regulated after culture. MIP‐1β, MIP‐3α and eotaxin did not stimulate B cell migration. Scattered information is available on B cell subset responses to chemokines. Therefore, we investigated the effects of MIP‐1α, MIP‐5, MCP‐1, MCP‐2, MCP‐3 and MDC on the in vitro locomotion of non‐germinal center (GC) (CD38^–) and GC (CD38⁺) B cells. All chemokines enhanced significantly (P < 0.001) the migration of the former, but not of the latter, cells. CCR1, CCR2 and CCR4 were detected by flow cytometry on non‐GC (i.e. naive and memory) B cells, whereas they were absent (CCR1 and CCR2) or poorly expressed (CCR4) on GC B cells.