IntroductionAdult bone marrow stromal cells supply the appropriate scaffold for hematopoiesis 1 and hematopoietic-cell homeostasis, 2 but can also differentiate in vitro in most, if not all, somatic cell types. 3,4 Due to their specific capability of generating multiple mesenchymal lineages, bone marrow-derived stromal progenitors have been designated mesenchymal stem cells (MSCs). 5 MSCs are clonogenic because they can be isolated from bone marrow and expanded ex vivo without any apparent modification in phenotype or loss of function. Based on these features, MSCs are considered a promising strategy for tissue engineering, repair of damaged tissues, and gene therapy, but their capacity to trans-differentiate also in vivo is still unresolved.Recently, another unforeseen feature of MSCs has been reported, namely, that MSCs can modulate many T-cell functions including cell activation. 6,7 Based on this, human MSCs (hMSCs) have been administered in vivo to improve the outcome of allogeneic transplantation by promoting hematopoietic engraftment 8 and to hamper graft-versus-host disease. 9 More recently, we have shown that systemic administration of MSCs to mice affected by experimental autoimmune encephalomyelitis (EAE), a prototypical disease mediated by self-reactive T cells, results in striking disease amelioration mediated by the induction of peripheral tolerance. 10 In addition, it has been shown that tolerance induction by MSCs may occur also through the inhibition of dendritic-cell maturation and function, 11-13 thus suggesting that activated T cells are not the only targets of MSCs. In contrast, the effects of hMSCs on B cells are unknown.B-cell development occurs in the bone marrow and is strictly dependent on close interaction of B-cell progenitors with stromal cells that produce cytokines capable of supporting B-cell survival and proliferation. 14,15 Thus, we investigated whether MSCs, which derive from the marrow stroma, affect mature B-cell functions. Here, we demonstrate that hMSCs significantly affect proliferation, differentiation, and chemotactic behavior of normal mature B cells, thus further supporting the possibility that administration of MSCs may represent a novel therapeutic strategy for immune-mediated disorders. Materials and methodsAliquots of bone marrow aspirates were obtained from healthy adult bone marrow donors and peripheral-blood (PB) samples were obtained from healthy adult blood donors after informed consent was obtained, per the Declaration of Helsinki. The ethical board of the G. Gaslini Institute approved the study. B-cell isolation and cultureMononuclear cells (MNCs) were isolated by Ficoll-Hypaque density gradient (Sigma Chemical, St Louis, MO) from the PB of 9 healthy donors. Cell suspensions were first depleted of lymphocytes forming rosettes with sheep red blood cells (T cells) and subsequently treated with magnetic activated cell sorting (MACS) CD19-conjugated microbeads, according to the instructions of the manufacturer (Miltenyi Biotech, Auburn, CA). (mAb). All cell cul...

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 hypermutated 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-␣, 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-␣, CXCL12, and CXCL13 in the CNS may provide favorable microenvironmental conditions for these events.A rich mononuclear cell infiltrate, comprised of macrophages, T cells, and, to a lesser extent, B cells, is typical of the multiple sclerosis (MS) lesion (1-3). So far, the majority of studies have addressed the characterization of T cells involved in the autoimmune attack to the CNS (1).A role of B cells in MS pathogenesis is suggested by the presence of oligoclonal Ig bands within the cerebrospinal fluid (CSF) that represent a hallmark of the disease (4). In addition, clonally expanded B cells accumulate in chronic MS lesions (5, 6) and in the CSF (7, 8) from MS patients. Finally, antimyelin Abs may be involved in demyelination (9) and may have prognostic value (10).Ectopic structures resembling classical lymphoid follicles (11, 12) may develop in the parenchyma of nonlymphoid tissues during the course of both autoimmune (13) and chronic infectious (14) diseases. Newly formed lymphoid follicles recently have been detected in the CNS from MS patients, indicating occurrence of lymphoid neogenesis supported by the CXL13 and CC chemokine ligand 21 chemokines (15).In this study, we characterize the B cell compartment within the CSF of subjects with MS and other inf lammatory neurological disorders (OIND) and demonstrate that a complete recapitulation of B cell differentiation occurs in the CSF, where favorable microenvironmental conditions have been identified. Materials...

IL-12 activates murine and human B cells, but little information is available as to the expression and function of IL-12R on human B lymphocytes. Here we show that the latter cells, freshly isolated from human tonsils, expressed the transcripts of both β1 and β2 chains of IL-12R and that β2 chain mRNA was selectively increased (4- to 5-fold) by incubation with Staphylococcus aureus Cowan I bacteria or IL-12. B cell stimulation with IL-12 induced de novo expression of the transcripts of the two chains of IL-18R, i.e., IL-1 receptor-related protein and accessory protein-like. Functional studies showed that both IL-12 and IL-18 signaled to B cells through the NF-κB pathway. In the case of IL-12, no involvement of STAT transcription factors, and in particular of STAT-4, was detected. c-rel and p50 were identified as the members of NF-κB family involved in IL-12-mediated signal transduction to B cells. IL-12 and IL-18 synergized in the induction of IFN-γ production by tonsillar B cells, but not in the stimulation of B cell differentiation, although either cytokine promoted IgM secretion in culture supernatants. Finally, naive but not germinal center or memory, tonsillar B cells were identified as the exclusive IL-12 targets in terms of induction of NF-κB activation and of IFN-γ production.

This study shows that SDF-1 substantially enhances the migration of follicular center lymphoma B cells but not the migration of freshly purified germinal center B cells. This difference may be related to the extended survival of follicular center lymphoma versus germinal center B cells. SDF-1 produced in follicular center lymphoma lymph nodes may play a role in the local dissemination of tumor cells.