Letteratura scientifica selezionata sul tema "MZ B cells"

We have previously characterized a human blood CD19+CD1c+IgM+CD27+CD21loCD10+ innate-like B-cell population, which presents features shared by both transitional immature and marginal zone (MZ) B-cells, named herein “precursor-like” MZ B-cells. B-cells with similar attributes have been associated with regulatory potential (Breg). In order to clarify this issue and better characterize this population, we have proceeded to RNA-Seq transcriptome profiling of mature MZ and precursor-like MZ B-cells taken from the blood of healthy donors. We report that ex vivo mature MZ and precursor-like MZ B-cells express transcripts for the immunoregulatory marker CD83 and nuclear receptors NR4A1, 2, and 3, known to be associated with T-cell regulatory (Treg) maintenance and function. Breg associated markers such as CD39 and CD73 were also expressed by both populations. We also show that human blood and tonsillar precursor-like MZ B-cells were the main B-cell population to express elevated levels of CD83 and NR4A1-3 proteins ex vivo and without stimulation. Sorted tonsillar precursor-like MZ B-cells exerted regulatory activity on autologous activated CD4+ T-cells, and this was affected by a CD83 blocking reagent. We believe these observations shed light on the Breg potential of MZ populations, and identify NR4A1-3 as potential Breg markers, which as for Tregs, may be involved in stabilization of a regulatory status. Since expression and activity of these molecules can be modulated therapeutically, our findings may be useful in strategies aiming at modulation of Breg responses.

Specialized B cells residing in the splenic marginal zone (MZ) continuously survey the blood for antigens and are important for immunity to systemic infections. However, the cues that uniquely attract cells to the MZ have not been defined. Previous work demonstrated that mice deficient in cannabinoid receptor 2 (CB2) have decreased numbers of MZ B cells but it has been unclear whether CB2 regulates MZ B cell development or positioning. We show that MZ B cells are highly responsive to the CB2 ligand 2-arachidonylglycerol (2-AG) and that CB2 antagonism rapidly displaces small numbers of MZ B cells to the blood. Antagonism for longer durations depletes MZ B cells from the spleen. In mice deficient in sphingosine-1-phosphate receptor function, CB2 antagonism causes MZ B cell displacement into follicles. Moreover, CB2 overexpression is sufficient to position B cells to the splenic MZ. These findings establish a role for CB2 in guiding B cells to the MZ and in preventing their loss to the blood. As a consequence of their MZ B cell deficiency, CB2-deficient mice have reduced numbers of CD1d-high B cells. We show that CB2 deficiency results in diminished humoral responses to a CD1d-restricted systemic antigen.

Abstract Development of hematopoietic cells depends on a dynamic actin cytoskeleton. Here we demonstrate that expression of the cytoskeletal regulator WASP, mutated in the Wiskott-Aldrich syndrome, provides selective advantage for the development of naturally occurring regulatory T cells, natural killer T cells, CD4+ and CD8+ T lymphocytes, marginal zone (MZ) B cells, MZ macrophages, and platelets. To define the relative contribution of MZ B cells and MZ macrophages for MZ development, we generated wild-type and WASP-deficient bone marrow chimeric mice, with full restoration of the MZ. However, even in the presence of MZ macrophages, only 10% of MZ B cells were of WASP-deficient origin. We show that WASP-deficient MZ B cells hyperproliferate in vivo and fail to respond to sphingosine-1-phosphate, a crucial chemoattractant for MZ B-cell positioning. Abnormalities of the MZ compartment in WASP−/− mice lead to aberrant uptake of Staphylococcus aureus and to a reduced immune response to TNP-Ficoll. Moreover, WASP-deficient mice have increased levels of “natural” IgM antibodies. Our findings reveal that WASP regulates both development and function of hematopoietic cells. We demonstrate that WASP deficiency leads to an aberrant MZ that may affect responses to blood-borne pathogens and peripheral B-cell tolerance.

Mice deficient for the transcriptional coactivator BOB.1/OBF.1 show several defects in B cell differentiation. Numbers of immature transitional B cells in the bone marrow are reduced and fewer B cells reach the periphery. Furthermore, germinal center B cells are absent and marginal zone (MZ) B lymphocytes are markedly reduced. Increased levels of B cell apoptosis in these mice prompted us to analyze expression and function of antiapoptotic proteins. Bcl2 expression is strongly reduced in BOB.1/OBF.1-deficient pre–B cells. When BOB.1/OBF.1-deficient mice were crossed with Bcl2-transgenic mice, B cell development in the bone marrow and numbers of B cells in peripheral lymphoid organs were normalized. However, neither germinal center B cells nor MZ B cells were rescued. Additionally, Bcl2 did not rescue the defects in signaling and affinity maturation found in BOB.1/OBF.1-deficient mice. Interestingly, Bcl2-transgenic mice by themselves show an MZ B cell defect. Virtually no functional MZ B cells were detected in these mice. In contrast, mice deficient for Bcl2 show a relative increase in MZ B cell numbers, indicating a previously undetected function of Bcl2 for this B cell compartment.

Marginal zone (MZ) B cells play a major role in the first-line responses against blood-born T-independent bacterial antigens (TI), but the full scope of their immune functions is not known. Here we compare the responses of MZ and follicular (FO) B cells to a T-dependent antigen (TD), hapten–(4-hydroxy-3-nitrophenyl)acetyl (NP) coupled to chicken γ-globulin, in a cell transfer system. Consistent with the conventional paradigm, MZ B cells but not FO B cells rapidly generated the early burst of NP-specific antibody-forming cells (AFC), high levels of IgM Ab, and early IgG with relatively high affinity to NP. However, MZ B cells were also capable of forming germinal centers (GCs) albeit with a delay, compared with FO B cells. The early AFCs and the GCs originated from different MZ precursors, but the MZ- and FO-derived GCs were similar in VH gene repertoire, somatic mutation, and production of late AFC and IgG Ab. Surprisingly, the MZ but not the FO memory response included IgM Ab. We conclude that MZ B cells are heterogeneous, comprising cells for both early AFC response and GC/memory pathway against TD antigens.

Marginal zone (MZ) B cells resemble fetally derived B1 B cells in their innate-like rapid responses to bacterial pathogens, but the basis for this is unknown. We report that the MZ is enriched in “fetal-type” B cell receptors lacking N regions (N−). Mixed bone marrow (BM) chimeras, made with adult terminal deoxynucleotidyl transferase (TdT)+/+ and TdT−/− donor cells, demonstrate preferential repertoire-based selection of N− B cells into the MZ. Reconstitution of irradiated mice with adult TdT+/+ BM reveals that the MZ can replenish N− B cells in adult life via repertoire-based selection and suggest the possibility of a TdT-deficient precursor population in the adult BM. The mixed chimera data also suggest repertoire-based bifurcations into distinct BM and splenic maturation pathways, with mature “recirculating” BM B cells showing a very strong preference for N+ complementarity-determining region (CDR) 3 compared with follicular B cells. Because the T1 and MZ compartments are both the most enriched for N− H-CDR3, we propose a novel direct T1→MZ pathway and identify a potential T1–MZ precursor intermediate. We demonstrate progressive but discontinuous repertoire-based selection throughout B cell development supporting multiple branchpoints and pathways in B cell development. Multiple differentiation routes leading to MZ development may contribute to the reported functional heterogeneity of the MZ compartment.

Perturbations in B cells are a hallmark of HIV-1 infection. This is signified by increased numbers of exhausted CD21neg memory B cells, driven by continuous antigen-specific and bystander activation. Using high-dimensional flow cytometry, we demonstrate that this exhausted phenotype is also prevalent among peripheral antigen-inexperienced naive and marginal zone (MZ) B cells in acute and chronic HIV-1 infection. A substantial fraction of naive and MZ B cells exhibit down-regulated CD21 levels and diminished response to B cell receptor (BCR)–dependent stimulation. Compared with CD21pos subsets, the CD21neg naive and MZ B cells differ in the expression of chemokine receptors and activation markers. Effective antiretroviral treatment normalizes peripheral naive and MZ B cell populations. Our results emphasize a more widely spread impairment of B cells in HIV-1 infection than previously appreciated, including antigen-inexperienced cells. This highlights the importance of monitoring functional capacities of naive B cells in HIV-1 infection, as exhausted CD21neg naive B cells may severely impair induction of novel B cell responses.

Here we show that marginal zone (MZ)-B cells in rats can already be detected in neonatal spleen from two days after birth. At this time point, morphologically distinct MZs are not present yet and the vast majority of B cells in spleen are located in a concentric area surrounding the T cell zones (PALS). Before MZs are obviously detectable in spleen (14 days after birth), MZ-B cells seem to be enriched at the outer zones of the concentric B cell areas. Similar to adult rats, neonatal MZ-B cells are intermediate-sized cells that express high levels of surface (s)IgM and HIS57 antigen, and low levels of sIgD and CD45R (HIS24). We show here, however, that in contrast to adult MZ-B cells, MZ-B cells (and also recirculating follicular (RF)-B cells) in neonatal rats express higher levels of CD90 (Thy-1). In adult rats, expression of CD90 on the B cell lineage is confined to immature B cells. We speculate that the expression of CD90 on neonatal MZ-B cells may have implications for their responsiveness to polysaccharide (T cell-independent type 2) antigens.

The splenic marginal zone (MZ) is comprised of specialized populations of B cells, dendritic cells, and macrophages that are uniquely arrayed outside the white pulp follicles to screen the blood for bacterial and other particulate Ags. Mechanisms responsible for MZ B-cell formation, localization, retention, and function are understood to include antigenic specificity, transcription factors, integrins, and surface receptors for soluble ligands such as S1P. Here, we add to this repertoire by demonstrating that the receptor for CXCL12, CXCR7, is expressed on MZ but not on follicular B cells. Treatment of mice with CXCR7 inhibitors led to disruption of MZ architecture, reduced numbers of MZ B cells, and altered granulocyte homeostasis associated with increasing serum levels of CXCL12. CXCR7 thus appears to function as a scavenger receptor for CXCL12 on MZ B cells.

Marginal zones (MZs) are microdomains in the spleen that contain various types of immune cells, including MZ B cells, MOMA1+ metallophilic macrophages, and mucosal addressin cell adhesion molecule 1 (MAdCAM-1)+ endothelial cells. MAdCAM-1+ and MOMA1+ cells line the sinus, that separates MZs from splenic follicles. Here we show that a receptor for the lysophospholipid sphingosine-1-phosphate (S1P), S1P3, is required for normal numbers of splenic immature and MZ B cells, and for S1P-induced chemotaxis of MZ B cells. S1P3 is also essential for proper alignment of MOMA1+ macrophages and MAdCAM-1+ endothelial cells along the marginal sinus. The lack of cohesion of the marginal sinus in S1P3−/− mice affects MZ B cell functions, as wild-type (WT) MZ B cells migrate more into S1P3−/− follicles than into WT follicles after treatment with lipopolysaccharide. Additionally, short-term homing experiments demonstrate that WT MZ B cells home to the S1P3−/− spleen in increased numbers, suggesting a role for the marginal sinus in regulating MZ B cells numbers. Moreover, S1P3−/− mice are defective in mounting immune responses to thymus-independent antigen type 2 due to defects in radiation-resistant cells in the spleen. These data identify lysophospholipids and the S1P3 receptor as essential regulators of the MZ sinus and its role as a barrier to the follicle.

Systemic lupus erythematosus (SLE) and Sj?gren?s syndrome (SS) are both heterogeneous autoimmune diseases with strong B cell aspects. A proportion of SLE and SS patients exhibit elevated serum BAFF (B cell activating factor of the TNF family); BAFF plays a key role in B cell homeostasis, survival and tolerance. BAFF transgenic (Tg) mice develop nephritis and salivary gland destruction that resemble aspects of SLE and SS respectively. Autoimmune disease development in BAFF Tg mice correlates with marginal zone (MZ) B cell expansion and the abnormal presence of MZ-like B cells outside of the spleen. The role of MZ B cells in BAFF induced autoimmune disease was analysed by crossing BAFF Tg mice with Lymphotoxin-β knockout mice (creating LTβ-BTg mice) which lack most peripheral lymph nodes, and also lack MZ B cells as a result of disrupted splenic architecture. LTβ-BTg mice were not protected against nephritis but exhibited reduced salivary gland infiltration and destruction. Indicating that the development of sialadenitis but not nephritis in BAFF Tg mice is MZ B cell dependent. Nephritis development in LTβ-BTg mice was associated with the detection of B-1 B cells in the inflamed kidneys. As B-1a B cell survival is dependent on the spleen, the contribution of B-1a B cells to nephritis development in BAFF Tg mice was assessed by crossing BAFF Tg mice to congenitally asplenic Hox11-/- mice (creating Hox11 -BTg mice). The absence of a spleen and B-1a B cells in Hox11-BTg mice delayed the nephritis development. In contrast, splenectomy of BAFF Tg mice at 12 weeks of age did not alter nephritis onset. In these mice B-1a B cells persisted in the peritoneal cavity and MZ-like B cells were detected in the periphery 8 months after surgery. In summary, nephritis development in BAFF Tg mice is unaltered by the absence of MZ B cells, but delayed in the absence of a spleen, MZ and B-1a B cells. Thus, B-1a and B-1b B cells may be potential targets for the treatment of nephritis in SLE patients with elevated BAFF.

La plupart des infections par le VIH-1 sont acquises lors de rapports hétérosexuels. En Afrique subsaharienne on observe 71 % des infections mondiales et 60 % des nouvelles infections par le VIH-1 touchent les femmes. Le tractus génital féminin (TGF) constitue la principale porte d’entrée pour le VIH-1 et joue un rôle important dans la défense de l’organisme contre les microorganismes pathogènes tout en maintenant une tolérance de la flore commensale. On y trouve les cellules épithéliales qui participent à l’élaboration des réponses immunes en collaboration avec les cellules dendritiques (DCs), mais également d’autres types de cellules immunitaires qui confèrent une protection à la muqueuse vaginale, notamment à travers la production de cytokines et de chimiokines. Nous avons établi une cohorte de travailleuses du sexe (CSWs) au Bénin et nous avons identifié des femmes hautement exposées et séronégatives au VIH-1 (HESN), qui demeurent séronégatives après plus de sept années actives dans le travail du sexe. Les personnes HESN étant un excellent modèle d’immunité naturelle contre le VIH-1, le but de notre projet consiste donc à étudier les cellules immunitaires impliquées dans la protection de l’hôte face au VIH-1, au niveau du tractus génital féminin. Nous émettons l’hypothèse que le maintien de faibles conditions inflammatoires dans le TGF des femmes HESN préviendrait une activation immunitaire excessive en préservant l’intégrité de la barrière de la muqueuse vaginale et contribuerait ainsi à maintenir une protection contre l’infection par le VIH-1. Des études antérieures sur les HESN béninoises et kenyanes ont démontré que ces femmes présentent de faibles niveaux d’inflammation dans leur TGF inférieur. En accord avec cela, nous avons observé de faibles niveaux de BLyS/BAFF dans la muqueuse vaginale des HESN comparativement aux travailleuses du sexe séropositives (CSWs+ HIV+). BLyS/BAFF est une molécule importante pour la différenciation des cellules B et pour la sélection de cellules B de première ligne de la zone marginale (MZ). De ce fait, nous rapportons pour la première fois la présence de cellules B CD1c+ de type MZ qui sont capables de se lier naturellement à la gp120 glycosylée, au niveau de la muqueuse vaginale. Or, des cellules B CD1c+ exprimant IgG sont augmentées chez les CSWs+ HIV+ comparativement aux HESN, ce qui pourrait contribuer à l’hyperglobulinémie observée dans le TGF inférieur des CSWs+ HIV+. Les faibles niveaux de BLyS/BAFF retrouvés dans la muqueuse vaginale des HESN semblent donc préserver une homéostasie au sein du compartiment B et des cellules B CD1c+ du TGF. De plus, nous y détectons une réactivité des IgG1 avec la gp-41 de l’enveloppe virale, qui pourrait contribuer à leur immunité naturelle. Avec les cellules épithéliales, les DCs sont l’une des premières à être en contact avec le virus dans le TGF. Elles jouent un rôle essentiel dans l’orchestration des réponses immunitaires. Nous pensons que les DCs contribuent au maintien de faibles conditions inflammatoires dans le TGF des HESN, prévenant ainsi l’activation immunitaire excessive et préservant l’intégrité de la barrière muqueuse de façon à maintenir une protection/contrôle contre le virus. Nous avons caractérisé une population myéloïde endocervicale « tolérogénique » HLA-DR+CD14+CD11c+ exprimant HLA-G, ILT4, CD103 et de forts taux d’IFN-α et d’IL-10 dont la fréquence relative était augmentée au niveau du col de l’utérus des HESN comparativement aux CSWs+ HIV+. De plus, des populations Tregs/Tr1 étaient aussi augmentées chez les HESN. Ces données reflètent à la fois une réponse antivirale et une contribution au contrôle des conditions inflammatoires dans le TGF des HESN. Afin de mieux comprendre la nature des cellules myéloïdes tolérogéniques, nous avons voulu dériver des monocytes en cellules dendritiques (MoDCs). Toutefois, nous avons remarqué que la différenciation des MoDCs des HESN était altérée. Suite à cela, nous avons caractérisé le profil transcriptomique des monocytes. Les résultats préliminaires mettent en lumière l’éventuel rôle des récepteurs nucléaires NR4A dans la modulation des MoDCs et, possiblement, sur le plan des cellules myéloïdes tolérogéniques chez les HESN. Dans l’ensemble, ces résultats nous ont permis d’acquérir de nouvelles connaissances sur les mécanismes mis en place chez les HESN dans l’immunité naturelle contre le VIH-1.
Most HIV-1 infections are acquired through heterosexual intercourse. In sub-Saharan Africa, 71% of global infections are observed and 60% of new HIV-1 infections affect women. The female genital tract (FGT) constitutes a main portal of entry for HIV-1 and plays an important role in protecting the host against pathogens while maintaining a tolerance to a commensal flora. FGT immunity involves genital epithelial cells as well as dendritic cells (DCs) and many other types of immune cells which confer protection, through the production of chemokines and cytokines. We established a cohort of commercial sex workers (CSWs) in Benin and identified HIV-1 highly exposed seronegative (HESN) individuals, who remain uninfected after more than seven years of active prostitution. These HESN individuals being an exceptional model of natural immunity against HIV-1, the aim of our project is to characterize immune cells involved in protection from HIV-1 infection, in the female genital tract. We hypothesize that maintenance of low inflammatory conditions in the FGT of HESN women helps to prevent excessive immune activation likely preserving the mucosal barrier integrity and would help to maintain a protection against HIV infection. Previous studies of Beninese and Kenyan HESN have shown that these women have a low inflammatory profile in their lower FGT. Accordingly, we found that vaginal mucosa of HESN had lower soluble BLyS/BAFF levels when compared to HIV-infected CSWs (CSWs+ HIV+). BLyS/BAFF is highly recognized for its role in B-cell ontogenesis, as well as cell fate decision towards the innate marginal zone (MZ) B-cell pool. For the first time, we report the presence of genital MZ-like CD1c+ B-cells that naturally bind to fully glycosylated gp120 in the vaginal mucosa. However, CD1c+ B-cells expressing IgG are increased in the lower FGT of CSWs+ HIV+ when compared to HESN, suggesting that these cells could contribute to the hyperglobulinemia observed in the lower FGT of CSWs+ HIV+. The low levels of BLyS/BAFF found in the vaginal mucosa of HESN thus appear to preserve homeostasis of the FGT B cell compartment and CD1c+ B-cells. In addition, we detect a reactivity of IgG1 to HIV-gp41 in cervico-vaginal lavages (CVL) supernatants of HESN, which could contribute to their natural immunity. Epithelial cells and DCs are one of the earliest cell types to sense the virus in the FGT. They play a key role in the orchestration of immune responses. We characterized a "tolerogenic" endocervical myeloid HLA-DR+CD14+CD11c+ population expressing HLA-G, ILT4, CD103 and high levels of IFN-α and IL-10, that was increased in the cervix of HESN when compared to CSWs+ HIV+. In addition, frequencies of Tregs/Tr1 cells were also increased in HESN. We believe that DCs contribute to maintaining low inflammatory conditions in the FGT of HESN, preventing excessive immune activation and preserving the integrity of the mucosal barrier to maintain a protection/control against the virus. These data reflect both an antiviral response and a contribution to the control of inflammatory conditions in the FGT of HESN. To better understand the nature of tolerogenic myeloid cells, we wanted to derive monocyte-derived dendritic cells (MoDCs). However, derivation of blood MoDCs was impaired in HESN. As a result, we decided to characterize the transcriptomic profile of total blood monocytes. Preliminary results appear to demonstrate the possible role of NR4A nuclear receptors in MoDCs modulation, and possibly in tolerogenic myeloid cells in HESN. Overall, our results contribute to a better understanding of the mechanisms established by HESN in natural immunity to HIV-1.