Association of IgG1 Antibody Clearance with FcγRIIA Polymorphism and Platelet Count in Infliximab-Treated Patients

The FcγRIIA/CD32A is mainly expressed on platelets, myeloid and several endothelial cells. Its affinity is considered insufficient for allowing significant binding of monomeric IgG, while its H131R polymorphism (histidine > arginine at position 131) influences affinity for multimeric IgG2. Platelet FcγRIIA has been reported to contribute to IgG-containing immune-complexe clearance. Given our finding that platelet FcγRIIA actually binds monomeric IgG, we investigated the role of platelets and FcγRIIA in IgG antibody elimination. We used pharmacokinetics analysis of infliximab (IgG1) in individuals with controlled Crohn’s disease. The influence of platelet count and FcγRIIA polymorphism was quantified by multivariate linear modelling. The infliximab half-life increased with R allele number (13.2, 14.4 and 15.6 days for HH, HR and RR patients, respectively). It decreased with increasing platelet count in R carriers: from ≈20 days (RR) and ≈17 days (HR) at 150 × 10⁹/L, respectively, to ≈13 days (both HR and RR) at 350 × 10⁹/L. Moreover, a flow cytometry assay showed that infliximab and monomeric IgG1 bound efficiently to platelet FcγRIIA H and R allotypes, whereas panitumumab and IgG2 bound poorly to the latter. We propose that infliximab (and presumably any IgG1 antibody) elimination is partly due to an unappreciated mechanism dependent on binding to platelet FcγRIIA, which is probably tuned by its affinity for IgG2.     

免疫磁性微球的制备及对IgG的分离

采用反相悬浮包埋法制备SPA-Sepharose免疫磁性微球,并对产物的结构、粒径、磁性能进行了表征,所得产物粒径大约为5μm,表面包裹葡萄球菌蛋白A(Staphylococcal Protein A,简称SPA),分散性较好,具有超顺磁性。利用SPA对免疫球蛋白G(IgG)的特异性吸附反应及磁性微球的超顺磁性,从猪血清中分离IgG,试验结果表明:SPA免疫磁性微球对猪血清的最大吸附效率是70.12%,可反复使用29次。     

β-乳球蛋白IgG抗原决定簇的识别

以β-乳球蛋白氨基酸序列为模板,错位合成β-乳球蛋白多肽,以收集到的牛乳过敏患者血清为抗体,鉴定β-乳球蛋白IgG抗原决定簇,探讨牛乳过敏机理．结果表明,β-乳球蛋白IgG抗原决定簇有2条,它们在β-乳球蛋白中的氨基酸序列定位分别为aa22—36和aa127—141．结果表明通过特异性水解抗原决定簇实现牛奶脱敏的方法是可行的．     

Application of N-succinimidyl 4-[(18)~F](fluoromethyl) benzoate to protein labeling

N-succinimidyl 4-[18F](fluoromethyl) benzoate for protein labeling was prepared (57%, EOB) in about 30min. Reaction conditions of S18FMB with IgG including pH of solutions, protein concentration, reaction temperature and time were studied. The optimal labeling conditions were: 0.2mg/mL IgG, pH = 7.8-8.5, 25℃, and reaction time 5min.Under these conditions the yield was about 80%. The 18F-labeled protein was purified by size exclusion chromatography.     

Application of an ultrahigh-resolution scanning electron microscope (UHS-T1) to biological specimens

In 1985 we developed an ultrahigh-resolution scanning electron microscope with a resolution of 0.5 nm. It is equipped with a field emission gun and an objective lens with a very short focal length. In this study we report a survey of some different preparation techniques and biological specimens using the new scanning electron microscope. Intracellular structures such as cell organelles were observed surprisingly sharper than those observed by ordinary scanning electron microscopes. However, at magnifications over 250,000 X, platinum particles could be discerned as scattered pebbles on the surface of all structures in coated materials. Using an uncoated but conductively stained specimen, we successfully observed ribosomes on a rough endoplasmic reticulum at a direct magnification of 1 million. In these images some protrusions were recognized on the ribosomes. Ferritin and immunoglobulin G were used as samples of biological macromolecules. These samples were observed without metal coating and conductive staining. The ferritin particles appeared as rounded bodies without any substructure on the surface and immunoglobulin G as complexes of three-unit bodies. In the latter the central body might correspond to the Fc fragment and two side ones to Fab fragments. We assume that ultrahigh-resolution scanning electron microscopy is an effective means for observation of the cell fine structures and biological macromolecules. It will open a new research field in biomedicine.     

IgG4相关性硬化性胆管炎:肝胆胰外科医生应该重视的内科疾病

IgG4相关性疾病(IgG4-related disease,IRD)是一类近10余年逐渐被认识的以血清IgG4升高、席纹状纤维化以及大量IgG4阳性浆细胞浸润为特征的多器官和系统受累的自身免疫性疾病。胆道是IRD常受累的器官之一。IgG4相关性硬化性胆管炎(IgG4 related sclerosing cholangitis,IRSC)是IRD在胆道的临床表现形式。IRSC多有胆管壁局限性增厚、胆管扩张以及梗阻性黄疸等与胆胰恶性肿瘤相类似的临床表现。IRSC对激素敏感,预后良好,合并恶性肿瘤罕见,绝大多数无需手术治疗,但近几年笔者临床工作中仍不时见到因"胆管扩张、梗阻性黄疸"行手术治疗,术后病理证实为IRSC的病例,回顾这些病例的诊治过程,鲜有术前考虑IRSC的情况。临床上也可见到术前因血清IgG4升高,起初误诊为IRSC,错过最佳手术时机,而术后病理证实为胆管癌的病例。故加强对IRSC的宣讲,特别是加深肝胆胰外科医生对IRSC的认识具有重要临床意义。     

EM>N-/EM>琥珀酰亚胺-3-碘［S

研究能有效降低抗体的体内脱碘的标记方法。碘标记N-琥珀酰亚胺-3-(三正丁基锡)苯甲酸酯(ATE)前体,得到N-琥珀酰亚胺-3-碘[125I]苯甲酸酯(S125IB),分别与人IgG和抗人肝癌单抗(Hepama-1)进行偶联,探索最佳标记条件,并测定标记物的稳定性和生物活性,研究直接标记和间接标记的Hepama-1在正常小鼠体内的生物学分布。结果表明,用N-氯代琥珀酰亚胺(NCS)法125I标记ATE前体,在ATE用量为25～100μg、NCS用量为10～20μg、磷酸盐缓冲溶液(PBS)用量为10～20μL、反应时间为5 min时,标记率大于95%;S125IB和人IgG的偶联率最高可达75%,偶联产物稳定性、生物活性良好;与Hepama-1偶联率可达75%以上。生物分布的对比实验证明,1,3,4,6-四氯-3α,6α-二苯甘脲(Iodogen)直接标记的Hepama-1在甲状腺的放射性摄取率(脱碘显示)最高是S125IB间接标记的Hepama-1的87.9倍。这说明以ATE为前体的放射性碘间接标记蛋白质方法与传统的碘直接标记方法相比较,在解决体内严重脱碘问题上具有明显的优越性。