Blockade of superoxide generation prevents high-affinity immunoglobulin E receptor-mediated release of allergic mediators by rat mast cell line and human basophils

BACKGROUND: Previous studies have shown that rat peritoneal mast cells and mast cell model rat basophilic leukaemia (RBL-2H3) cells generate intracellular reactive oxygen species (ROS) in response to antigen challenge. However, the physiological significance of the burst of ROS is poorly understood. OBJECTIVE: The present study was undertaken to investigate the role of superoxide anion in mediator release in rat and human cell systems. METHODS: RBL-2H3 cells were directly stimulated with anti-rat FcepsilonRI alpha-subunit monoclonal antibody (mAb). For the analysis of human cell system, leucocytes were isolated by dextran sedimentation from healthy volunteers or from patients, and challenged either with anti-human FcepsilonRI mAb or with the relevant antigens. Superoxide generation was determined by chemiluminescence-based methods. The releases of histamine and leukotrienes (LT)s were determined by enzyme-linked immunosorben assay (ELISA). RESULTS: Cross-linking of FcepsilonRI on RBL-2H3 cells or on human leucocytes from healthy donors by the anti-FcepsilonRI mAb resulted in a rapid generation of superoxide anion, as determined by chemiluminescence using superoxide-specific probes. Similarly, leucocytes from patients generated superoxide anion in response to the challenge with the relevant allergen but not with the irrelevant allergen. Furthermore, diphenyleneiodonium (DPI), a well-known inhibitor of flavoenzymes suppressed the superoxide generation and the release of histamine and LTC4 induced by the anti-FcepsilonRI mAb or by allergen in parallel. CONCLUSION: These results indicate that both RBL-2H3 cells and human basophils generate superoxide anion upon FcepsilonRI cross-linking either by antibody or by allergen challenge and that blockade of the generation prevents the release of allergic mediators. The findings strongly support the role of superoxide generation in the activation of mast cells and basophils under both physiological and pathological conditions. The findings suggest that drugs regulating the superoxide generation have potential therapeutic use for allergic disorders.     

Human serum IgE-mediated mast cell degranulation shows poor correlation to allergen-specific IgE content

BACKGROUND: Although allergen-specific IgE content in serum can be determined immunochemically, little is known about the relationship between this parameter and the strength of the degranulation response upon allergen triggering. OBJECTIVES: Analyse the degranulation capacity of immunochemically defined purified and serum IgE after challenge with anti-IgE or allergen using a rat mast cell line (RBL) transfected with the alpha-chain of the human high-affinity IgE receptor (FcepsilonRI). METHODS: Purified IgE specific for 4-hydroxy-3nitrophenylacetyl, purified IgE of unknown specificity, and sera from allergic patients sensitive to Dermatophagoides pteronyssinus and Dactylis glomerata were assessed. Degranulation was measured by a beta-hexosaminidase release assay after anti-IgE or allergen-specific challenge. RESULTS: For purified monoclonal IgE a significant correlation (r = 0.97) was found between the proportion of bound allergen-specific IgE and the strength of the degranulation response. In contrast, no correlation (r = 0.27) was detected after sensitization with serum IgE. CONCLUSION: Our studies demonstrate that mast cell activation mediated through IgE from allergic patients is a result of complex relationships that are not only dependent on allergen-specific IgE content but also relate to the capacity to efficiently sensitize and trigger the signalling responses that lead to degranulation.     

Genetic regulation of thymic involution

In this review, we have summarized our work using combined complex statistical genetics, bioinformatics, and functional genomics to determine the genetic basis of the age-related thymic involution in C57BL/6J X DBA/2J recombinant inbred mice and the parental B6 and D2 mice. We have shown that these mice provided a valuable genetic model that can permit resampling of thymuses from different aged but genetically identical animals and determination of the relative significance of age-associated changes in the thymus. Our results suggest that the quantitative trait loci (QTL) regulating the Con A-induced thymocyte proliferative response were mapped to mouse chromosome Chr 11 (D11Mit51 at 18 cM), a region that harbors the IL-12b gene. The importance of IL-12b in maintaining thymic integrity and function during the aging process was confirmed by a more rapid involution of the thymus in IL-12b knockout (IL-12b-/-) mice compared to wild-type (WT) mice. Functionally, IL-12 provided a strong synergistic effect to augment the IL-7 or IL-2 induced thymocyte proliferative response, especially in both aged WT and IL-12b-/- mice, but not in normal young mice. In contract to the proliferative response, the age-related decline in the total number of thymocytes was determined at different age, and mapped to loci on Chr 9, 62 cM and Chr 10, 32 cM. Using matrix-assisted laser desorption/ionisation-time of flight-mass spectrometry (MALDI-TOF-MS), increased expression of peroxiredoxin was found to be correlated with thymic involution. Our results suggest the possibility to identify the complex molecular network that can be associated with the regulation of thymic involution in aged mice using a high-dimensional functional genomics approach.     

Differential induction of human monocyte transforming growth factorβ1 production and its regulation by interleukin 4

We have previously shown that trauma patients' monocytes which arein vivo activated by multiple injury-induced mediators have elevated transforming growth factor-beta (TGF) bioactivity. Interleukin-4 (IL-4), a Th₂ and B lymphocyte stimulatory factor, has been shown to inhibit monocyte production of a number of mediators both after lipopolysaccharide stimulation and after trauma-induced stimulation. However, IL-4 inhibitory effects appears to vary, depending on the mixture of inducing stimuli. Here we describe thein vitro IL-4 inhibition of human monocyte TGF bioactivity using several stimulation induction protocols: muramyl dipeptide stimulation alone, or after FcRI (CD64) cross-linking induction, interferon-gamma (IFN) priming, or trauma-generatedin vivo mediator induction. IL-4 suppressed both muramyl dipeptide-induced TGF bioactivity and TGF mRNA in a dose-dependent fashion and was most effective when IL-4 was administered at initiation of normal monocyte stimulation. Muramyl dipeptide (MDP)-induced increases in trauma patients' monocyte TGF bioactivity were also inhibited by high doses of IL-4 (25 ng/ml). FcRI cross-linking increased MDP-induced normal monocyte TGF bioactivity, but this increase could be consistently inhibited only by very high IL-4 concentrations (50 ng/ml). IL-4 did not consistently downregulate MDP-induced TGF bioactivity in IFN-primed monocytes. IL-4 can suppress monocyte TGF production, as well as other monocyte mediators, but its efficiency depends on the stimuli combination present in the microenvironment.     

Two QTLs Located on Chromosomes 1 and 5 Modulate Different Aspects of the Performance of Mice of the B × D Ty RI Strain Series in the Morris Navigation Task

The Morris navigation task is widely used to study spatial abilities in rodents; namely, to analyze the effects of mutations in genetically engineered mice. Although quantitative and Mendelian genetic studies have shown that the variation of these abilities is partly under genetic control, little is known about these genetic factors. In order to analyze the genetic architecture of spatial navigation in mice, a wide genome scan was performed to map the QTLs that control various aspects of the performance, using the RI strain methodology. Latencies to locate the submerged platform across learning sessions and performance to the spatial probe test were analyzed in the 26 strains of the B × D RI series. Both cluster analysis of behavioral measurements and QTL mapping confirmed previous data showing that the escape latencies and the spatial bias rely on two distinct components of the task, controlled by different loci. A QTL on chromosome 1 influenced escape latencies during the four training sessions, whereas another QTL, located on chromosome 5, was shown to control spatial performance at the probe trial and also exhibited epistatic interactions with two other QTLs on chromosomes 2 and 13. The function of these QTLs is examined in the broader context of hippocampal-dependent learning processes and in relation to QTLs already found in similar positions in other behavioral traits.     

Regulation of mast cell signaling through high-affinity IgE receptor by CD45 protein tyrosine phosphatase

The transmembrane tyrosine phosphatase CD45 regulates the activity of src family protein tyrosine kinases (PTK) and thereby influences the signaling via such receptors as T and B cell antigen receptors associated with these PTK. However, its implication in signaling through the mast cell receptor with high affinity for IgE (FcepsilonRI) is less clear, although Lyn, a member of the src family, plays an important role in FcepsilonRI-mediated signaling. To define a role for CD45 in FcepsilonRI signal transduction, we established CD45 high expressing rat basophilic leukemia cell lines (RBL-CD45H) and cell lines expressing trace amounts of CD45 (RBL-CD45L). We demonstrate that although all RBL-CD45L cell lines degranulate following IgE- and antigen-induced FcepsilonRI aggregation, the response is significantly reduced at a low dose of antigen. The cells show a delayed and slowed Ca(2+) mobilization even though at a higher dose where the cells degranulate to a similar extent as RBL-CD45H. This diminished Ca(2+) response is restored by reconstitution of RBL-CD45L with a chimeric molecule containing the cytoplasmic phosphatase domains of rat CD45. Furthermore, tyrosine phosphorylation of FcepsilonRI, association of FcepsilonRI with Lyn and PTK activity associated with FcepsilonRI, all of which are enhanced upon FcepsilonRI aggregation in RBL-CD45H, are impaired in RBL-CD45L. Finally, we show that FcepsilonRI is physically associated with CD45 in RBL-CD45H prior to receptor aggregation. Thus, we propose that, although not indispensable in mast cell degranulation, CD45 positively regulates the signaling through FcepsilonRI by promoting the activation of FcepsilonRI-associated Lyn.     

Chimeric Fc receptors identify immunoglobulin-binding regions in human FcγRII and FcϵRI

FcγRII and Fc?RI are functionally distinct cell surface receptors for immunoglobulin (Ig); FcγRII binds IgG with low affinity, whereas Fc?RI binds IgE with high affinity, yet they are homologous in structure and sequence having extracellular regions containing two Ig-like domains with 38% amino acid identity. Chimeric receptors derived from human FcγRII and FcγRI were produced by exchanging homologous regions of the two receptors to define binding region(s) for IgG in FcγRII and IgE in Fc?RI. Firstly, a chimeric form of the Fc?RI α chain was produced by replacing the transmembrane region and cytoplasmic tail with that of FcγRII. This mutant α chain could be expressed on the cell surface independently of associated β and γ subunits, and retained high-affinity IgE binding, indicating that the extracellular region of the FcγRI α chain is sufficient for high-affinity IgE binding. Secondly, to identify the role of the individual domains in Fc binding of both FcγRII and FcγRI, chimeric receptors were generated by exchanging the first extracellular domains between FcγRII and the α chain mutant and used to demonstrate that the second extracellular domain of both receptors contains region(s) directly involved in Ig binding. Additional chimeric receptors were constructed to localize the Ig interactive regions in domain two of FcγRII and FcγRI; these identified a single region of IgG binding in FcγRII located between residues Ser¹³⁶ to Val¹⁶⁹, and at least three independent IgE binding regions in the FcγRI α chain, between residues Trp⁸⁷ to Lys¹²⁸, Tyr¹²⁹ to Asp¹⁴⁵, and Ser¹⁴⁶ to Val¹⁶⁹.     

彩色多普勒血流成像血流阻力指数联合形态影像在良恶性卵巢肿瘤鉴别中的应用研究

目的:探讨彩色多普勒血流成像(CDFI)血流阻力指数联合形态影像在良恶性卵巢肿瘤鉴别中的应用价值。方法:选取医院接诊的73例卵巢肿瘤患者,将其不同检查方法的影像资料分为观察组和对照组,观察组采用超声形态影像联合血流阻力(RI)指数进行检查;对照组采用二维超声形态影像检查。将RI值和形态诊断进行5分法量化处理,绘制受试者工作特征(ROC)曲线,比较两组ROC曲线下面积(AUC)以及诊断的准确率。结果:73例患者中良性肿瘤35例,恶性肿瘤38例。对照组良恶性卵巢肿瘤的总阳性率为86.30%(63/73),低于观察组的97.26%(71/73),差异有统计学意义(x~2=5.811,P<0.05)。以病理结果为标准,观察组和对照组的AUC分别为0.964和0.803,观察组的诊断价值高于对照组。结论:CDFI联合形态影像的检查方法能对卵巢肿瘤的血流进行定量和定性分析,血流阻力指数为提高良恶性肿瘤鉴别的准确率提供重要依据。     

99mTc-DTPA肾动态显像在小儿先天性肾积水的应用

目的探讨肾功能临床相关指标对小儿先天性肾积水的诊断价值.方法用99mTc-DTPA核素动态显像测定68只患肾和14只正常肾的肾小球滤过率(GFR),并与年龄及血清尿素氮(BUN)、血清肌酐(SCr)、血红蛋白(Hb)进行相关性分析.结果 GFR与正常儿童年龄呈正相关(r=0.428,P＜0.05);中、重度肾积水患儿GFR与Hb呈正相关(分别为r=0.341、P＜0.05,r=0.635、P＜0.01);GFR与BUN只在重度肾积水呈负相关(r=-0.559,P＜0.05);GFR与SCr呈显著负相关(r=-0.445,P＜0.01);中、重度肾积水肾功能显著性下降(P＜0.05,P＜0.001),轻度积水肾与正常肾肾功能无显著性差异(P＞0.05).结论 GFR与SCr是检测小儿先天性肾积水肾功能的理想指标;BUN不适于肾积水的早期诊断;临床诊断明确的小儿先天性肾积水应早期手术治疗,以防止肾功能下降至失代偿而造成局部和全身性损害.     

间接ELISA法测定转基因小鼠血清中核糖核酸酶抑制因子的表达

[目的]建立间接ELISA法测定血清中核糖核酸酶抑制因子(ribonuclease inhibitor,RI)含量的方法,并测定在转RI基因小鼠血清中RI的表达情况。[方法]用血清样品包被酶标板,兔抗人RI抗体为一抗,辣根过氧化物酶标记的羊抗兔IgG为二抗,建立血清RI定量检测的间接ELISA法;取转染了RI基因的小鼠的血清,用上述建立的间接ELISA法测定不同时相小鼠血清中RI的表达水平。[结果]定量检测血清RI的间接ELISA法最适反应条件为一抗最佳稀释度为1∶4000,二抗的最佳稀释浓度为1∶2000。转基因小鼠第2、3周血清中RI含量较低(0.556±0.080),1个月左右达到最高值(0.836±0.113),3个月时明显下降(0.640±0.100)。[结论]间接ELISA法可以用于测定血清中的RI抗原含量。