Expression of Recombination Activating Genes in Germinal Center B Cells: Involvement of Interleukin 7 (IL-7) and the IL-7 Receptor

Mouse germinal center (GC) B cells have been shown to undergo secondary V(D)J (V, variable; D, diversity; J, joining) recombination (receptor editing) mediated by the reexpressed products of recombination activating gene (RAG)-1 and RAG-2. We show here that interleukin (IL)-7 as well as IL-4 was effective in inducing functional RAG products in mouse IgD⁺ B cells activated via CD40 in vitro. Blocking of the IL-7 receptor (IL-7R) by injecting an anti– IL-7R monoclonal antibody resulted in a marked suppression of the reexpression of RAG-2 and subsequent V(D)J recombination in the draining lymph node of immunized mice, whereas RAG-2 expression was not impaired in immunized IL-4–deficient mice. Further, these peripheral B cells activated in vitro or in vivo were found to express IL-7R. These findings indicate a novel role for IL-7 and IL-7R in inducing receptor editing in GC B cells.     

Antiviral Protection and Germinal Center Formation, But Impaired B Cell Memory in the Absence of CD19

Coligation of CD19, a molecule expressed during all stages of B cell development except plasmacytes, lowers the threshold for B cell activation with anti-IgM by a factor of 100. The cytoplasmic tail of CD19 contains nine tyrosine residues as possible phosphorylation sites and is postulated to function as the signal transducing element for complement receptor (CR)2. Generation and analysis of CD19 gene–targeted mice revealed that T cell–dependent (TD) antibody responses to proteinaceous antigens were impaired, whereas those to T cell–independent (TI) type 2 antigens were normal or even augmented. These results are compatible with earlier complement depletion studies and the postulated function of CD19. To analyze the role of CD19 in antiviral antibody responses, we immunized CD19^−/− mice with viral antigens of TI-1, TI-2, and TD type. The effect of CD19 on TI responses was more dependent on antigen dose and replicative capacity than on antigen type. CR blocking experiments confirmed the role of CD19 as B cell signal transducer for complement. In contrast to immunization with protein antigens, infection of CD19^−/− mice with replicating virus led to generation of specific germinal centers, which persisted for >100 d, whereas maintenance of memory antibody titers as well as circulating memory B cells was fully dependent on CD19. Thus, our study confirms a costimulatory role of CD19 on B cells under limiting antigen conditions and indicates an important role for B cell memory.     

Interleukin 6 Dependence of Anti-DNA Antibody Production: Evidence for Two Pathways of Autoantibody Formation in Pristane-induced Lupus

Pristane induces a lupus-like syndrome in nonautoimmune mice characterized by the development of glomerulonephritis and lupus-associated autoantibodies. This is accompanied by overproduction of interleukin (IL)-6, a cytokine linked with autoimmune phenomena. The goal of this study was to evaluate the role of IL-6 in autoantibody production in pristane-induced lupus. BALB/cAn IL-6–deficient (−/−) and –intact (+/+) mice were treated with pristane or phosphate-buffered saline, and autoantibody production was evaluated. Pristane induced high levels of immunoglobulin (Ig)G anti-single-stranded DNA, –double-stranded (ds)DNA, and -chromatin antibodies in IL-6^+/+, but not IL-6^−/− mice by enzyme-linked immunosorbent assay. High titer IgG anti-dsDNA antibodies also were detected in sera from +/+, but not −/−, mice by Crithidia luciliae kinetoplast staining. The onset of IgG anti-dsDNA antibody production in +/+ mice occurred >5 mo after pristane treatment, well after the onset of nephritis, suggesting that these antibodies are not directly responsible for inducing renal disease. In contrast to anti-DNA, the frequencies of anti-nRNP/Sm and anti-Su antibodies were similar in pristane-treated IL-6^−/− and IL-6^+/+ mice. However, levels were higher in the +/+ group. These results suggest that IgG anti-DNA and chromatin antibodies in pristane-treated mice are strictly IL-6 dependent, whereas induction of anti-nRNP/Sm and Su autoantibodies is IL-6 independent. The IL-6 dependence of anti-DNA, but not anti-nRNP/Sm, may have implications for understanding the patterns of autoantibody production in lupus. Anti-DNA antibodies are produced transiently, mainly during periods of disease activity, whereas anti-nRNP/Sm antibody levels are relatively insensitive to disease activity. This may reflect the differential IL-6 dependence of the two responses.     

抗C3d单抗制备及免疫金层析法的建立

目的 研制抗C3d单抗,建立免疫金层析法检测血浆补体片段C3d,判断补体活化情况。方法 用菊糖—C3d作抗原,免疫Balb/c小鼠,并制备杂交瘤,以羊抗C3包被酶标反应板并结合C3d为检测板,筛选分泌抗C3d单抗的杂交瘸。利用protein G柱亲和层析提取抗C3d单抗IgG和C3d结合物,进行SDS-PAGE电泳,鉴定单抗的特异性。将抗C3d单抗标以胶体金,制备免疫金层析测试余。通过在免疫金中加未标金的抗C3d单抗(游离单抗)来调整试纸条的灵敏度,并测定C3d。结果 SDS-PAGE电泳图上,出现IgG的重链、轻链、及C3d 3个条带;金标记抗C3d单抗的试条(Ⅰ)测C3d的灵敏度在6—10ng/m1,当加入0．1μg/m1游离抗C3d单抗(Ⅱ)后,灵敏度为10—15ng/m1。利用两种试条灵敏度的不同,对轻、中重型肝炎检测,结果轻型肝炎患者在纸条Ⅰ上阳性率为83．3％(25/30),纸条Ⅱ全为阴性,中重型肝炎者在纸条Ⅰ、Ⅱ的阳性率为100％(30/30)。结论 用本试验建立的免疫金层析法测定肝炎患者血浆C3d水平,可判断补体活化程度,辅助乙型肝炎轻、重分型。     

人组织激肽释放酶6双抗夹心ELISA方法的建立及临床初步应用

目的通过制备的人组织型激肽释放酶6(hK6)单克隆抗体(mAb),建立双抗夹心酶联免疫吸附测定(ELISA)检测方法,并用于胃癌诊断。方法采用该实验室保存的hK6重组蛋白,免疫BALB/c小鼠后通过杂交瘤技术制备特异性的mAb,经鉴定纯化、酶标记后,建立双抗夹心ELISA方法,检测胃癌患者血清中hK6水平,并联合检测血清中的癌胚抗原(CEA)水平,探讨hK6作为胃癌生物标记的可行性。结果成功建立了检测血清中hK6的双抗夹心ELISA方法,并确定该方法包被抗体的最适浓度为5μg/mL,酶标记抗体的最佳稀释比例为1∶2 000。该方法检测各组血清中的hK6水平,与胃溃疡组hK6水平[(3.59±1.02)ng/mL]和健康体检组hK6水平[(3.35±0.67)ng/mL]比较,胃癌组hK6水平[(5.78±1.66)ng/mL]明显高于其他两组,差异有统计学意义(P0.05);而胃溃疡组与健康体检组hK6水平比较,差异无统计学意义(P0.05)。胃癌患者hK6和CEA检测的阳性率分别为69.70%和45.46%,两者联合检测的阳性率为78.79%。结论成功建立了hK6双抗夹心ELISA检测方法;hK6是较好的胃癌血清肿瘤标记物,同时检测hK6与CEA可提高胃癌的检出率,减少漏诊的发生,有助于胃癌的诊断。     

Somatic hypermutation in MutS homologue (MSH)3-, MSH6-, and MSH3/MSH6-deficient mice reveals a role for the MSH2-MSH6 heterodimer in modulating the base substitution pattern

Although the primary function of the DNA mismatch repair (MMR) system is to identify and correct base mismatches that have been erroneously introduced during DNA replication, recent studies have further implicated several MMR components in somatic hypermutation of immunoglobulin (Ig) genes. We studied the immune response in mice deficient in MutS homologue (MSH)3 and MSH6, two mutually exclusive partners of MSH2 that have not been examined previously for their role in Ig hypermutation. In Msh6(-)/- and Msh3(-)/-/Msh6(-)/- mice, base substitutions are preferentially targeted to G and C nucleotides and to an RGYW hot spot, as has been shown previously in Msh2(-)/- mice. In contrast, Msh3(-)/- mice show no differences from their littermate controls. These findings indicate that the MSH2-MSH6 heterodimer, but not the MSH2-MSH3 complex, is responsible for modulating Ig hypermutation.     

Evaluation of complement system proteins C3a,C5a and C6 in patients of endometriosis

BackgroundEndometriosis is a disease that shows auto-immune and chronic characteristics, suggesting a role for proteins mediating immune interactions in its pathophysiology. The aim was to evaluate C3a and C5a for their role in inflammatory responses and C6 as the down-stream interactor following our previous findings on C5 mRNA expression changes in endometriosis [1].MethodsSera from 71 endometriosis patients and 77 women without endometriosis were taken. While the samples were taken only once from the controls, the patient samples were taken before, in 1st and in 7th days after laparoscopy. Levels of complement proteins C3a, C5a and C6 were measured with ELISA assays. MPV (Mean Platelet Volume), CRP (C-Reactive Protein) and NLR (Neutrophil-to-Leukocyte Ratio) were also analyzed from the retrospective data.ResultsC6 levels of early-stage patients at postoperative 1st day were significantly higher than controls. Patients with high MPV measurements had significantly higher C3a (p < 0.0001) and C6 (p < 0.05) levels than controls at all times of measurement.ConclusionsC6, an integral component of the membrane attack complex (MAC), could play a role at early disease-stage. The changes in levels of complement proteins and their relation to high MPV levels suggest a broader area of interplay for immune interactors in endometriosis. Although a bigger and longitudinal study design is needed to obtain more accurate results to evaluate these proteins as potential biomarkers, an important role of complement system within the pathophysiology of endometriosis is apparent.     

C5a delays apoptosis of human neutrophils via an extracellular signal-regulated kinase and Bad-mediated signalling pathway

AIMS: We recently demonstrated that complement fragment C5a delays apoptosis of human neutrophils via induction of the phosphatidylinositol-3 kinase (PI 3-K) pathway. In the present study, we examined whether C5a modulates neutrophil survival through the extracellular signal-regulated kinase (ERK) and Bad-mediated signalling pathway. METHODS: Human neutrophils were isolated by percoll gradient and preincubated for 1 h with or without PD98059 (20 microM), a specific ERK inhibitor, followed by incubation with C5a (1 microg mL(-1)) for 24 h. Apoptosis was quantified by flow cytometry, using propidium iodide nuclear staining. Extracellular signal-regulated kinase downstream signalling events were evaluated by measuring the expression of cytosolic total and phosphorylated p44/p42 proteins, and Bad phosphorylation using immunoblot analyses. These time-dependent analyses were performed over a brief exposure to C5a (0-30 min). Modulation of cytosolic caspase-9 and caspase-3 activity was measured by Western blot analyses. RESULTS: C5a inhibited neutrophil apoptosis (P=0.04), which was abrogated in the presence of PD98059 (P=0.04). Time-dependent effect of C5a on p44/p42 phosphorylation was rapid, peaked at 5 min, and was abrogated by the ERK inhibitor (P=0.04). In addition, brief stimulation of neutrophils with C5a induced phosphorylation of Bad, which was inhibited by the ERK inhibitor (P=0.03). Further, C5a suppressed the proteolytic cleavage of caspase-9 and caspase-3, which was reversed by ERK inhibition. Finally, blockade of both the ERK (with PD98059) and PI 3-K (with wortmannin) pathways did not induce additive inhibition of neutrophil apoptosis by C5a. CONCLUSION: This study demonstrates that in addition to the PI 3-K pathway, C5a also inhibits neutrophil apoptosis via an ERK-signalling pathway, resulting in phosphorylation of Bad and blockade of proteolytic cleavage of caspases. The activation of this additional survival-signalling pathway may be another important cellular mechanism that enhances neutrophil survival in inflammatory states.     

Regulatory mechanisms of C4b‐binding protein (C4BP)α and β expression in rat hepatocytes by lipopolysaccharide and interleukin‐6

Summary. Background: C4b‐binding protein (C4BP), a multimeric protein structurally composed of α chains (C4BPα) and a β chain (C4BPβ), regulates the anticoagulant activity of protein S (PS). Patients with sepsis have increased levels of plasma C4BP, which appears to be induced by interleukin (IL)‐6. However, it is not fully understood how lipopolysaccharide (LPS) and IL‐6 affect the plasma C4BP antigen level and C4BPα and C4BPβ expression in hepatocytes. Objectives: To assess the effect of LPS and IL‐6 on plasma C4BP, PS–C4BP complex levels, PS activity, and C4BP expression by rat liver in vivo and on C4BP expression by isolated rat hepatocytes in vitro. Results: Plasma C4BP antigen level transiently decreased from 2 to 12 h after LPS (2 mg kg^?1) injection, and then it abruptly increased up to 24 h after LPS injection. Plasma C4BP antigen level increased until 8 h after IL‐6 (10 μg kg^?1) injection, and then gradually decreased up to 24 h after IL‐6 injection. LPS significantly decreased the protein and mRNA expression of both C4BPα and C4BPβ in rat hepatocytes, and this effect was inhibited by NFκB and MEK/ERK inhibitors. IL‐6 mediated increase in C4BPβ expression in rat hepatocytes, which leads to increased plasma PS–C4BP complex level and to decreased plasma PS activity, was inhibited by inhibition of STAT‐3. Conclusion: LPS decreases both C4BPα and C4BPβ expression via the NFκB and MEK/ERK pathways, whereas IL‐6 specifically increases C4BPβ expression via the STAT‐3 pathway, causing an increase in plasma PS–C4BP complex, and thus decreasing the anticoagulant activity of PS.