A self-sustaining layer of early-life-origin B cells drives steady-state IgA responses in the adult gut

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IgA production by peritoneal cavity B cells is IL-6 independent: Implications for intestinal IgA response

We have shown previously both in vitro and in vivo that IL-6 is an important factor for the development of IgA-producing B cells. However, despite the lack of this cytokine in mice with targeted disruption of the interleukin (IL)-6 gene (gene knockout mice), a substantial number of IgA-producing plasma cells occur in their intestinal mucosa. The experiments reported here indicate that there is a population of IgA-producing B cell precursors originating from the peritoneal cavity, distinguished from conventional Peyer's patch-derived precursors by their expression of CD5, and that IgA secretion by these cells is IL-6-independent. Further, there is an increase in CD5 expression among brightly staining IgA-producing cells obtained from the intestinal lamina propria of IL-6 gene-disrupted mice compared to normal controls. These data suggest an explanation for the persistence of IgA-producing plasma cells in the intestinal mucosa of IL-6-depleted mice and indicate the importance of IL-6 for development of conventional precursors of IgA-producing B cells, but not those derived from the peritoneal cavity pool.     

DC细胞和过渡性B细胞水平与IgA肾病患者病理分型及患者预后不良的关系

目的探讨过渡性B淋巴细胞、树突细胞(dendritic cells, DCs)水平与IgA肾病(IgA nephropathy,IgAN)患者病理分型的关系及对患者预后不良的预测价值。方法选取2012年1月至2016年1月我院收治的85例IgAN患者以及同期108例健康体检者作为研究对象。采用免疫荧光法检测肾组织DC数目和分布情况,采用流式细胞仪检测外周静脉血中CD19+CD27-CD38hi细胞水平,对IgAN患者进行肾脏组织病理分型,并分析DC细胞和过渡性B细胞与临床病理指标及预后之间的关系。结果研究组IgAN患者肾小球和肾小管间质组织中的CD209细胞水平高于健康对照组,外周血中CD19+CD27-CD38hi占B淋巴细胞百分率低于对照组(P<0.05)。肾小球、肾小管间质的DC数目、免疫荧光DC水平与牛津病理分型具有相关性(P<0.05)。Spearman相关分析显示,肾小管间质中DC数目与肾小管间质纤维化比例、肾小球硬化比例之间存在显著正相关性(P<0.05),CD19+CD27-CD38hi细胞比例与血尿素氮、血肌酐、尿蛋白量、肾小球硬化比例、节段性硬化比...     

Mast cells and inflammatory mediators in chronic ulcerative colitis

Chronic ulcerative colitis (CUC) is an inflammatory destructive disease of the large intestine characterized by motility and secretion disorders. In the past decade, attention has been paid to the role of neuronal structures and mast cells in regulating inflammatory and immune responses in inflammatory bowel disease (IBD). The present study was performed to demonstrate neuronal fibres (NF) and cells containing substance P (SP), tryptase and serotonin (SER) in the colonic wall of patients with CUC in remission. Biopsy specimens of 6 patients with CUC were investigated with immunocytochemical methods. Normal colon tissue obtained from 6 patients with rectal carcinoma was used as a control. An increased number of SP- and SER-positive NF was found in all the layers of the intestinal wall. The number of SER-containing endocrine cells in the mucosal glands was also increased per crypt. Tryptase-, SP- and SER-immunopositive mast cells were found in higher amounts than in control specimens in close apposition to the basal lamina of the glands among the epithelial cells and in other layers of the gut wall. Two types of mast cells were found: mast cells containing both tryptase and SP, and mast cells containing tryptase only. It is concluded that interactions between neuronal elements and mast cells play a significant role in the progress and maintenance of inflammatory processes in CUC.     

Regulatory functions of innate-like B cells

Innate-like B cells (ILBs) are heterogeneous populations of unconventional B cells with innate sensing and responding properties. ILBs in mice are composed of B1 cells, marginal zone (MZ) B cells and other related B cells. ILBs maintain natural IgM levels at steady state, and after innate activation, they can rapidly acquire immune regulatory activities through the secretion of natural IgM and IL-10. Thus, ILBs constitute an important source of IL-10-producing regulatory B cells (Bregs), which have been shown to play critical roles in autoimmunity, inflammation and infection. The present review highlights the latest advances in the field of ILBs and focuses on their regulatory functions. Understanding the regulatory activities of ILBs and their underlying mechanisms could open new avenues in manipulating their functions in inflammatory, infectious and other relevant diseases.     

Scarcity of autoreactive human blood IgA+ memory B cells

Class‐switched memory B cells are key components of the “reactive” humoral immunity, which ensures a fast and massive secretion of high‐affinity antigen‐specific antibodies upon antigenic challenge. In humans, IgA class‐switched (IgA⁺) memory B cells and IgA antibodies are abundant in the blood. Although circulating IgA⁺ memory B cells and their corresponding secreted immunoglobulins likely possess major protective and/or regulatory immune roles, little is known about their specificity and function. Here, we show that IgA⁺ and IgG⁺ memory B‐cell antibodies cloned from the same healthy humans share common immunoglobulin gene features. IgA and IgG memory antibodies have comparable lack of reactivity to vaccines, common mucosa‐tropic viruses and commensal bacteria. However, the IgA⁺ memory B‐cell compartment contains fewer polyreactive clones and importantly, only rare self‐reactive clones compared to IgG⁺ memory B cells. Self‐reactivity of IgAs is acquired following B‐cell affinity maturation but not antibody class switching. Together, our data suggest the existence of different regulatory mechanisms for removing autoreactive clones from the IgG⁺ and IgA⁺ memory B‐cell repertoires, and/or different maturation pathways potentially reflecting the distinct nature and localization of the cognate antigens recognized by individual B‐cell populations.     

Delineation of producing ability of IgG and IgA subclasses by naive B cells in newborn infants and adult individuals

Neonatal B cells with the naive (sIgD⁺) phenotype are able to generate IgG- and IgA-producing cells as well as IgM production in the presence of memory CD4⁺ T cells expressing L-selectin (CD62L) in pokeweed mitogen-stimulated cultures. We used this system to examine comparatively the ability of naive B cells to produce IgG and IgA subclasses in newborn infants and adult individuals. Naive B cells were enriched from both donors on the basis of sIgD positivity, and memory (CD45RO⁺) CD4⁺ T cells with CD62L expression were isolated from adults. We here demonstrate some differences in profiles of IgG and IgA subclass production between neonatal and adult naive B cells. In neonatal B cells, IgG1 and IgG3 were predominantly produced, but IgG2 and IgG4 production was virtually absent. Similar to neonatal B cells, adult naive B cells produced mainly IgGq and IgG3, although memory (sIgD’) B cells from adults secreted all of the IgG subclasses. It should be noted that low but detectable levels of IgG2 and IgG4 were found in adults’naive B cell cultures. Although IgA produced by neonatal B cells was exclusively IgA1, IgA2-secreting cells were identifiable in adult naive B cells. The results suggest that further class switch of naive B cells to IgG2, IgG4 and IgA2 in addition to IgG1 and IgG3 may be controlled by their own age-dependent maturation process.     

Mast cells in allergic asthma and beyond

Mast cells have been regarded for a long time as effector cells in IgE mediated type I reactions and in host defence against parasites. However, they are resident in all environmental exposed tissues and express a wide variety of receptors, suggesting that these cells can also function as sentinels in innate immune responses. Indeed, studies have demonstrated an important role of mast cells during the induction of life-saving antibacterial responses. Furthermore, recent findings have shown that mast cells promote and modulate the development of adaptive immune responses, making them an important hinge of innate and acquired immunity. In addition, mast cells and several mast cell-produced mediators have been shown to be important during the development of allergic airway diseases. In the present review, we will summarize findings on the role of mast cells during the development of adaptive immune responses and highlight their function, especially during the development of allergic asthma.     

Human bone marrow-derived IgA is produced by IgA-committed B cellsin vitro

Although human bone marrow has been implicated in the production of serum immunoglobulins, little information is available concerning the kinetics of antibody production (primary- or secondary-type humoral response) or the cells that are responsible for antibody production in human bone marrow. In this study, the kinetics of and cells responsible for antibody production in the bone marrow were investigated. Previous studies have demonstrated that human bone marrow mononuclear cells secrete a significant amount of IgAin vitro. This finding led to the focus of the present investigation on bone marrow IgA production. The results reported here demonstrate that IgA was synthesized de novo in cultures of bone marrow mononuclear cells; its peak concentration in the culture supernatants preceded that of IgM; its production was totally inhibited by the addition of microgram quantities of anti--chain antiserum, while milligram quantities of anti--chain antiserum were required for even partial inhibition of IgA production; and the culture of isolated IgA-bearing cells resulted in a greater than 13-fold increase in IgA concentration in the culture supernatants as compared with those from unseparated bone marrow mononuclear cells. From this study, it was concluded that bone marrow produces IgA as a secondary or anamnestic response to some undetermined stimulus and that IgA-committed B cells residing in, although probably not stimulated in, the bone marrow compartment were responsible for the IgA synthesis and secretionin vitro.     

Mast cells and the nodal sinus reaction in breast cancer

Mast cell counts in the sinuses of axillary nodes from breast cancer patients are shown to vary with the type of sinus reaction present. Few scattered mast cells were found in association with sinus histiocytosis. A mixed reaction, in which fewer histiocytes were present and more round cells, was accompanied by a significant increase in mast cell count, which in sinus catarrh showed a decrease. The possible role of sinus mast cells in relation to tumour spread is discussed.     

Evidence that intestinal IgA plasma cells in {micro},{varkappa} transgenic mice are derived from B-1 (Ly-1 B) cells

B6-Sp6 transgenic mice carry fully rearranged (BALB/c-derived,Igh-C^a allotype) µ. heavy chain and light chain transgenes,specific for trinitrophenyl, on a C57BL background (Igh-C^b allotype).FACS analyses show that the majority of B cells in peripherallymphoid organs and bone marrow(BM) express transgenic IgM exclusively.A small proportion of the B cells, however, express endogenousIgM, usually concomitant with transgenic IgM. Three criteriaestablish that the endogenous IgM expressing B cells belongto the B-1 cell lineage. (I) Endogenous IgM expressing B cellsin B6-Sp6 mice have the same localization pattern as B-1 cellsfrom normal animals: they are enriched in the peritoneal cavity.(II) The endogenous IgM⁺ B cells have the phenotype of B-1 cells:the endogenous IgM⁺ peritoneal B cells express Mac-1 (CD11b)and low levels of IgD, and most also express CD5 (L-1). (III)B6-Sp6 BM poorly reconstitutes endogenous IgM⁺ B cells, justas adult BM from normal mice poorly reconstitutes B-1 cells.In contrast, B cells which only express the transgene are readilyreconstituted by B6-Sp6 BM. The few endogenous IgM⁺ cells inthe B6-Sp6 BM recipients are located in the peritoneal cavityand have the phenotype of B-1b cells (previously the Ly-1 Bsister population), which are known to be reconstituted by adultBM.Two-color immunofluorescence staining of tissue sectionsfrom the gut and from isolated gut lamina propria cells showsthe presence of many IgA containing cells, about one-third ofwhich simultaneously express cytoplasmic (transgenic) IgM. TheC-region of this IgA is produced by endogenous C a genes, becausethe transgene encodes only for C_µ. Furthermore, the majorityof gut IgA containing cells do not express the Idiotype of thetransgene, indicating that most of the gut IgA cells are encodedby endogenous V_H genes and thus the result of an isotype switchfrom endogenous IgM expressing B cells. Since the endogenousIgM⁺ cells are B-1 cells (both B-1a and B-1b), the data stronglyindicate that the intestinal IgA plasma cells also belong tothe B-1 cell lineage.     

Cellular origins of human polymeric and monomeric IgA: enumeration of single cells secreting polymeric IgA1 and IgA2 in peripheral blood, bone marrow, spleen, gingiva and synovial tissue

Using modified ELISA and spot-ELISA, which permit the parallel determination of heavy chain subclass and the presence of covalently linked J chain, we analysed IgA found in cell culture supernatants or secreted by individual cells from peripheral blood, spleen, bone marrow, gingiva and synovial tissue, with respect to its polymeric or monomeric IgA form (pIgA, mIgA) and IgA1 or IgA2 subclass. The ELISA for determination of J chain in tissue culture supernatants was specific and highly sensitive (detection limit in pg). The results demonstrated that IgA1-producing cells predominated in the tissues examined, and that J chain could be detected in association with the majority of IgA1 and IgA2 secreted by individual cells. With respect to the frequency of cells secreting polymeric, J chain-containing IgA, only 20-30% of cells from the bone marrow were engaged in the synthesis of PIgA. In other tissues the frequency of cells secreting pIgA1 and pIgA2 was considerably higher. Peripheral blood mononuclear cells secreting pIgA2 were easily inducible during stimulation with T cell-dependent pokeweed mitogen, whereas Epstein-Barr virus-transformed cells secreted preferentially mIgA1. When the frequencies of pIgA-, pIgA1- or pIgA2-secreting cells (determined by spot-ELISA technique) from different tissues were correlated with the proportion of pIgA to mIgA (and IgA subclasses) secreted in tissue culture supernatants, data obtained suggest that many individual IgA-producing cells could be engaged in simultaneous secretion of mIgA and pIgA.     

Mast cells and angiogenesis in gastric carcinoma

Previous studies have shown that increased vascularity is associated with haematogenous metastasis and poor prognosis in gastric cancer. The role of mast cells in gastric cancer angiogenesis has not been clarified completely. In this study, we correlated microvascular density and tryptase‐ and chymase‐positive mast cells with histopathological type in gastric cancer. Specimens of primary gastric adenocarcinomas obtained from 30 patients who had undergone curative gastrectomy were investigated immunohistochemically by using anti‐CD31 antibody to stain endothelial cells and anti‐tryptase and anti‐chymase antibodies to stain mast cells. The results showed that stage IV gastric carcinoma has a higher degree of vascularization than other stages and that both tryptase‐ and chymase‐positive mast cells increase in parallel with malignancy grade even if the density of chymase‐positive mast cells was significantly lower than the density of tryptase‐positive mast cells and is highly correlated with the extent of angiogenesis. This study has demonstrated that mast cell density correlates with angiogenesis and progression of patients with gastric carcinoma. Understanding the mechanisms of gastric cancer angiogenesis provides a basis for a rational approach to the development of an antiangiogenic therapy in patients with this malignancy.     

Aberrant T-regulation in rheumatoid arthritis and IgA nephropathy affects CD5+ and CD5- B lymphocytes equally.

T-suppressor function and T-helper function in healthy adults, elderly patients with non-immune diseases, and patients with rheumatoid arthritis (RA) and IgA nephropathy (IgAN) were titrated by adding graded concentrations of CD8+ cells to autologous CD8-depleted peripheral blood mononuclear cells (PBMC), or CD4+ cells to CD8- 4- PBMC, respectively. Following culture with pokeweed mitogen (PWM), numbers of CD5+ and CD5- immunoglobulin-secreting cells were determined using a combination of rosetting with anti-CD5-coated Dynabeads and reverse haemolytic plaque formation (Jones, 1990). Of 11 RA patients studied, eight had slightly reduced suppressor activity for CD5+ and CD5- IgM-secreting cells, and three with active disease and high serum levels of C-reactive protein, could not suppress IgG, IgA or IgM secretion by either B subset. Helper activity for both CD5+ and CD5- B cells was slightly but significantly increased in RA patients. One of eight patients with IgAN could not suppress IgG, IgA or IgM production by CD5+ or CD5- B cells, and all IgAN patients required strikingly fewer CD4+ cells for PWM-induced activation of CD5+ and CD5- B cells than controls. It was concluded that in two immunologically mediated diseases in which some patients have raised numbers of circulating CD5+ B cells, aberrant T-regulation affects CD5+ and conventional CD5- B cells equally.     

Mast cells at the host-pathogen interface: host-protection versus immune evasion in leishmaniasis

Infection of a susceptible host with Leishmania, a protozoan parasite, causes the disease leishmaniasis, which is characterized by neutrophil, eosinophil, macrophage, lymphocyte and mast cell infiltration into the infected tissue followed by parasite growth. Although the roles played by other cells in leishmaniasis are known, the role of mast cells remains to be ascertained. Here, we demonstrate that Leishmania regulates mast cell infiltration to the site of infection, mast cell production and mast cell function resulting in differential growth of the parasite in resistant (C57BL/6 or CBA/T6T6) and susceptible (BALB/c) macrophages. An interleukin-3-dependent augmentation in mast cell committed progenitors is observed in BALB/c but not in C57BL/6 mice during Leishmania infection. The mast cell supernatants inhibit IFN-gamma-dependent restriction of Leishmania growth in macrophages in BALB/c mice whereas the reverse phenomenon occurs in C57BL/6 mice. Our data reveals a different facet of host-pathogen interaction.