Advance in research on recycling antibody / 生物工程学报

Monoclonal antibodies have become the main type of antibody drug because of their high specificity and strong affinity to antigen. However, with the intensive study of the natural monoclonal antibody, many defects have faced, such as the limit times of binding to antigen, the unanticipated antibody clearance and antigen accumulation. Therefore, studies are no longer limited to the natural antibody screening, but rather to improve the efficiency of antibody drugs by engineering. In recent years, the bottlenecks in the development of conventional antibody have been solved effectively since the discovery of a novel recycling antibody. Recycling antibody binds to an antigen in plasma and dissociates from the antigen in endosome, thus maximizing the use of antibody and reducing antigen-mediated antibody clearance and antibody-mediated antigen accumulation. In addition, recycling antibodies can enhance the affinity with Fc receptors through further Fc modification. This paper reviews the research progress of circulating antibodies, including its characteristics, transformation methods and prospects.

Caracterización de una muestra de pacientes chilenos con periodontitis y frecuencia del polimorfismo H131R en el receptor FcγRIIa / Characterization of a sample Chilean patients with periodontitis and frequency of H131R polymorphism in the FcγRIIa receptor

RESUMEN: Los receptores Fcγ947; (FcγR), específicos para la inmunoglobulina G, les confieren a las células donde se expresan funciones en la respuesta inmunoinflamatoria. La heterogeneidad interindividual en la eficiencia de la función de los FcγR se ha explicado por polimorfismos en los genes que codifican 3 de estos receptores, FcγRIIa, FcγRIIIa y FcγRIIIb, los cuales han sido asociados con susceptibilidad y/o severidad en enfermedades infecciosas y autoinmunes en diferentes poblaciones. En este trabajo se analizan las características clínicas de 94 pacientes chilenos con evidencia de daño periodontal y se establece la frecuencia alélica/genotípica del polimorfismo H131R en el gen FCGR2A que codifica para el receptor FcγRIIa, así como su posible asociación con periodontitis. El polimorfismo G>A (H131R) en el gen FCGR2A se estudió por PCR en tiempo real utilizando sondas TaqMan. En el grupo estudiado se encontró un alto porcentaje de pacientes con periodontitis (86, 2%) y una asociación significativa a edad y sexo. No se observó una asociación a los alelos H o R, ni a los genotipos encontrados (H/R y R/R). Este es el primer trabajo en que se estudia el polimorfismo H131R en el FcγRIIa en población chilena en una muestra de pacientes adecuadamente caracterizados; sin embargo, creemos que es necesario estudiar un mayor número de sujetos para determinar si los polimorfismos de los genes FcγR constituyen o no posibles factores de susceptibilidad a enfermedad periodontal en población chilena.

ABSTRACT: The Fcγ receptors (FcγR) specific for the immunoglobulin G, expresses for the immune inflammatory response function. The inter individual heterogeneity in the efficiency of the FcγR function has been explained by polymorphisms in genes that encode for 3 of these receptors, FcγRIIa, FcγRIIIa and FcγRIIIb, which have been associated with susceptibility or severity in autoimmune and infectious diseases in different populations. This paper discusses the clinical characteristics of 94 Chilean patients with evidence of periodontal damage and establishes the allelic/genotypic frequency of polymorphism H131R in the FCGR2A gene, which encodes for the receptor FcγRIIa, as well as their possible association with periodontitis. Polymorphism G>A (H131R) in the gene FCGR2A was studied via real time PCR using TaqMan probes. In the study group, a high percentage of patients with periodontitis was found (86, 2%) with a significant association with age and gender. No determination could be reached as to whether the allele H or R or the genotypes found (H/R and R/R) were a factor of genetic susceptibility. This is the first study to determine the polymorphisms of the FcγR gene in a Chilean population adequately characterized; nevertheless, we believe that it is necessary to study a greater number of subjects in order to determine if the polymorphisms of the FcγR gene are a possible factors of susceptibility to periodontal disease in the Chilean population.

IgG Fc engineering to modulate antibody effector functions

Therapeutic monoclonal antibodies are among the most effective biotherapeutics to date. An important aspect of antibodies is their ability to bind antigen while at the same time recruit immune effector functions. The majority of approved recombinant monoclonal antibody therapies are of the human IgG1 subclass, which can engage both humoral and cellular components of the immune system. The wealth of information generated about antibodies has afforded investigators the ability to molecularly engineer antibodies to modulate effector functions. Here, we review various antibody engineering efforts intended to improve efficacy and safety relative to the human IgG isotype. Further, we will discuss proposed mechanisms by which engineering approaches led to modified interactions with immune components and provide examples of clinical studies using next generation antibodies.

Pharmacokinetics of monoclonal antibodies and Fc-fusion proteins

There are many factors that can influence the pharmacokinetics (PK) of a mAb or Fc-fusion molecule with the primary determinant being FcRn-mediated recycling. Through Fab or Fc engineering, IgG-FcRn interaction can be used to generate a variety of therapeutic antibodies with significantly enhanced half-life or ability to remove unwanted antigen from circulation. Glycosylation of a mAb or Fc-fusion protein can have a significant impact on the PK of these molecules. mAb charge can be important and variants with pI values of 1-2 unit difference are likely to impact PK with lower pI values being favorable for a longer half-life. Most mAbs display target mediated drug disposition (TMDD), which can have significant consequences on the study designs of preclinical and clinical studies. The PK of mAb can also be influenced by anti-drug antibody (ADA) response and off-target binding, which require careful consideration during the discovery stage. mAbs are primarily absorbed through the lymphatics via convection and can be conveniently administered by the subcutaneous (sc) route in large doses/volumes with co-formulation of hyaluronidase. The human PK of a mAb can be reasonably estimated using cynomolgus monkey data and allometric scaling methods.

Glycosylation engineering of therapeutic IgG antibodies: challenges for the safety, functionality and efficacy

Glycosylation of the Fc region of IgG has a profound impact on the safety and clinical efficacy of therapeutic antibodies. While the biantennary complex-type oligosaccharide attached to Asn297 of the Fc is essential for antibody effector functions, fucose and outer-arm sugars attached to the core heptasaccharide that generate structural heterogeneity (glycoforms) exhibit unique biological activities. Hence, efficient and quantitative glycan analysis techniques have been increasingly important for the development and quality control of therapeutic antibodies, and glycan profiles of the Fc are recognized as critical quality attributes. In the past decade our understanding of the influence of glycosylation on the structure/function of IgG-Fc has grown rapidly through X-ray crystallographic and nuclear magnetic resonance studies, which provides possibilities for the design of novel antibody therapeutics. Furthermore, the chemoenzymatic glycoengineering approach using endoglycosidase-based glycosynthases may facilitate the development of homogeneous IgG glycoforms with desirable functionality as next-generation therapeutic antibodies. Thus, the Fc glycans are fertile ground for the improvement of the safety, functionality, and efficacy of therapeutic IgG antibodies in the era of precision medicine.

The Implication and Significance of Beta 2 Microglobulin: A Conservative Multifunctional Regulator / 中华医学杂志(英文版)

<p><b>OBJECTIVE</b>This review focuses on the current knowledge on the implication and significance of beta 2 microglobulin (β2M), a conservative immune molecule in vertebrate.</p><p><b>DATA SOURCES</b>The data used in this review were obtained from PubMed up to October 2015. Terms of β2M, immune response, and infection were used in the search.</p><p><b>STUDY SELECTIONS</b>Articles related to β2M were retrieved and reviewed. Articles focusing on the characteristic and function of β2M were selected. The exclusion criteria of articles were that the studies on β2M-related molecules.</p><p><b>RESULTS</b>β2M is critical for the immune surveillance and modulation in vertebrate animals. The dysregulation of β2M is associated with multiple diseases, including endogenous and infectious diseases. β2M could directly participate in the development of cancer cells, and the level of β2M is deemed as a prognostic marker for several malignancies. It also involves in forming major histocompatibility complex (MHC class I or MHC I) or like heterodimers, covering from antigen presentation to immune homeostasis.</p><p><b>CONCLUSIONS</b>Based on the characteristic of β2M, it or its signaling pathway has been targeted as biomedical or therapeutic tools. Moreover, β2M is highly conserved among different species, and overall structures are virtually identical, implying the versatility of β2M on applications.</p>

Identificação de peptídeos de Escherichia coli capazes de inibir a própria fagocitose em sepse / Identification of Escherichia coli peptides that can inhibit its own phagocytosis in sepsis

Introdução: Sepse é uma síndrome complexa definida por resposta inflamatória sistêmica, de origem infecciosa e caracterizada por manifestações múltiplas que podem determinar disfunção ou falência de um ou mais órgãos ou sistemas. É a principal causa de morte em unidades de terapia intensiva em pacientes críticos e tem representado uma fonte constante de preocupação para os sistemas de saúde em todo o mundo, devido, principalmente, às taxas elevadas de morbimortalidade. O tratamento da sepse é um desafio e continua a ser uma tarefa difícil devido a inúmeros fatores interferentes. Um estudo do nosso grupo demonstrou que a Escherichia coli (E. coli) é capaz de se ligar CD16 de um modo independente de opsonina, levando a um aumento na resposta inflamatória e a inibição da sua própria fagocitose, por conseguinte, procurou-se identificar os peptídeos no proteoma da E. coli envolvidos neste cenário. Metodologia: Utilizando a metodologia de Phage Display, que consiste numa técnica de clonagem, que permite a expressão de diversas sequências de peptídeos na superfície de bacteriófagos, nós identificamos 2 peptídeos que obtiveram interação com CD16. Após a seleção dos peptídeos identificamos uma proteína de membrana de E.coli que possui alta similaridade com um de nossos peptídeos selecionados. Nós acreditamos que esta proteína de membrana possa estar envolvida no processo de evasão imune desenvolvida pela E.coli e parece ser um forte candidato como uma nova opção terapêutica para controlar infecções por E. coli. Conclusão: A identificação de proteínas capazes de induzir inibição de fagocitose, através do receptor CD16, pode ser usada como uma nova forma de tratamento da sepse, assim como explorada no tratamento de doenças autoimunes.

Introduction: Sepsis is a complex syndrome defined by a systemic inflammatory response of infectious origin and characterized by multiple manifestations that can determine dysfunction/failure of one or more organs and systems. It is the leading cause of death in intensive care units and represents a major health problem around the world, mainly due to its high mortality and morbidity rates. The treatment of sepsis is challenging and remains a difficult task due to numerous interfering factors. A study from our group demonstrated that Escherichia coli (E. coli) is able to bind CD16 in an opsoninindependent manner, leading to an increase in the inflammatory response and inhibition of its own phagocytosis, therefore we sought to identify the peptides in the E. coli proteome involved in this scenario. Methods and Results: Using the Phage Display technique, which is a cloning technique that allows the expression of various peptide sequences on the surface of bacteriophages (phages) and selecting these on the basis of affinity for a target molecule, we identified two peptides that interact with CD16. Next, using bioinformatic tools, we found an E. coli membrane protein that has high similarity with one of our selected peptides. We believe this membrane protein is involved in the process of immune evasion developed by E. coli and it is a strong candidate as a new therapeutic option to control E. coli infections. Conclusion: The identification of proteins capable of inducing inhibition of phagocytosis through the CD16 receptor, can be used as a new treatment of sepsis, as well as exploited in the treatment of autoimmune diseases.

Mechanisms of Cross-protection by Influenza Virus M2-based Vaccines

Current influenza virus vaccines are based on strain-specific surface glycoprotein hemagglutinin (HA) antigens and effective only when the predicted vaccine strains and circulating viruses are well-matched. The current strategy of influenza vaccination does not prevent the pandemic outbreaks and protection efficacy is reduced or ineffective if mutant strains emerge. It is of high priority to develop effective vaccines and vaccination strategies conferring a broad range of cross protection. The extracellular domain of M2 (M2e) is highly conserved among human influenza A viruses and has been utilized to develop new vaccines inducing cross protection against different subtypes of influenza A virus. However, immune mechanisms of cross protection by M2e-based vaccines still remain to be fully elucidated. Here, we review immune correlates and mechanisms conferring cross protection by M2e-based vaccines. Molecular and cellular immune components that are known to be involved in M2 immune-mediated protection include antibodies, B cells, T cells, alveolar macrophages, Fc receptors, complements, and natural killer cells. Better understanding of protective mechanisms by immune responses induced by M2e vaccination will help facilitate development of broadly cross protective vaccines against influenza A virus.

Expression of neonatal Fc receptor on human nephritis and rat nephritis models / 中华病理学杂志

<p><b>OBJECTIVE</b>To study the expression of neonatal Fc receptor in podocytes in human nephritis and immune-induced rat nephritis models: anti-Thy1.1 nephritis and Heymann nephritis.</p><p><b>METHODS</b>Thirty-nine cases of renal biopsies were enrolled from September 2009 to February 2010, including 8 cases of minimal change disease, 4 cases of focal segmental glomerulosclerosis, 9 cases of membranous nephropathy, 12 cases of IgA nephropathy and 6 cases of lupus nephritis. Five normal kidney tissue samples adjacent to renal clear-cell carcinoma were served as normal controls. Laser capture microdissection and real-time RT-PCR were used to assess the expression level of FcRn mRNA in glomeruli of various glomerulonephritides, and immunohistochemistry (IHC) of FcRn by SuperVision method was performed. In addition, rat models of mesangial proliferative nephritis (anti-Thy1.1 nephritis) and passive membranous nephropathy (Heymann nephritis) were established and FcRn was examined in renal tissues by IHC.</p><p><b>RESULTS</b>The FcRn mRNA level in lupus nephritis was statistically higher than that of normal controls (P < 0.05). FcRn protein expression by IHC was seen in lupus nephritis (6/6), membranous nephropathy (6/9) and IgA nephropathy (7/12), significantly higher than that of normal controls (0/5), P < 0.05. Minimal change disease and focal segmental glomerular sclerosis showed minimal or none expression of FcRn (1/8, 0/4 respectively) and not statistically difference from that of normal controls. Furthermore, FcRn expression in podocytes was detected in rat anti-Thy1.1 (3/5) and Heymann nephritis models (2/7) but was not detected in normal controls.</p><p><b>CONCLUSIONS</b>Expression of FcRn in podocytes was up-regulated in immune-induced human nephritis and rat nephritis models of anti-Thy1.1 nephritis and Heymann nephritis. FcRn may play a role in the development of immune-induced glomerulonephritis.</p>

Immunization with HBsAg-Fc fusion protein induces a predominant production of Th1 cytokines and reduces HBsAg level in transgenic mice / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>The Fc receptor associated pathway might improve the immune responses against hepatitis B virus (HBV) as previously described by us. In addition, the Flt3 ligand (FL) has been reported to potentiate antigen presenting cells in vivo and may act as a potential adjuvant to boost antigen-specific immune responses. In this study, the immune efficacies of a set of fusion proteins of HBsAg and Fc and/or FL were evaluated in HBsAg transgenic mice.</p><p><b>METHODS</b>The fusion proteins composed of HBsAg and the Fc domain of murine IgG1 (HBsAg-Fc) and/or the Flt3 ligand, and yeast-derived recombinant HBsAg were used as immunogen to immunize HBsAg transgenic mice, respectively. Serum and liver HBsAg levels, serum anti-HBsAg and cytokine profile, and the activities of alanine aminotransferase (ALT)/AST were investigated after immunization.</p><p><b>RESULTS</b>After six injections, the most pronounced decrease in serum and liver HBsAg levels was observed in the HBsAg-Fc immunized group. In addition, serum Th1 cytokines and ALT/AST activities were highest in this group, indicating an effective induction of a favorable cellular immune response. Interestingly, the fusion protein containing HBsAg-Fc and the Flt3 ligand stimulated an alternative Th1-type immune response featured with high level productions of tumor necrosis factor α (TNF-α) and monocyte chemoabstractant protein 1 (MCP-1), causing a more severe cytotoxicity in hepatocytes while showed less effective in reducing serum HBsAg level.</p><p><b>CONCLUSION</b>HBsAg-Fc is effective in eliciting both the humoral and cellular immune responses against HBsAg in HBsAg transgenic mice, which makes it a potential immunogen for the immunotherapy of chronic hepatitis B.</p>

Dexamethasone Induces FcgammaRIIb Expression in RBL-2H3 Cells

Mast cells are involved in allergic responses, protection against pathogens and autoimmune diseases. Dexamethasone (Dex) and other glucocorticoids suppress FcepsilonRI-mediated release of inflammatory mediators from mast cells. The inhibition mechanisms were mainly investigated on the downstream signaling of Fc receptor activations. Here, we addressed the effects of Dex on Fc receptor expressions in rat mast cell line RBL-2H3. We measured mRNA levels of Fc receptors by real-time PCR. As expected, Dex decreased the mRNA levels of activating Fc receptor for IgE (FcepsilonR) I and increased the mRNA levels of the inhibitory Fc receptor for IgG FcgammaRIIb. Interestingly, Dex stimulated transcriptions of other activating receptors such as Fc receptors for IgG (FcgammaR) I and FcgammaRIII. To investigate the mechanisms underlying transcriptional regulation, we employed a transcription inhibitor actinomycin D and a translation inhibitor cycloheximide. The inhibition of protein synthesis without Dex treatment enhanced FcgammaRI and FcgammaRIII mRNA levels potently, while FcepsilonRI and FcgammaRIIb were minimally affected. Next, we examined expressions of the Fc receptors on cell surfaces by the flow cytometric method. Only FcgammaRIIb protein expression was significantly enhanced by Dex treatment, while FcgammaRI, FcgammaRIII and FcepsilonRI expression levels were marginally changed. Our data showed, for the first time, that Dex regulates Fc receptor expressions resulting in augmentation of the inhibitory receptor FcgammaRIIb.

Influence of consumption of probiotics on presence of enterobacteria in the oral cavity

Clinical benefits of probiotics have been clearly reported in different gastrointestinal disorders, many of them caused by enterobacteria. The oral cavity is a port of entry and can be an important reservoir of these microorganisms. This work evaluated whether consumption of probiotics was able to influence the presence of enterobacteria in the oral cavity and the specific secretory response against these microorganisms. Saliva samples of healthy individuals were collected and plated in MacConkey agar. Carriers of Gram-negative, rod-shaped microorganisms in the oral cavity were selected and instructed to use the probiotic Yakult LB for 20 days. Saliva was then collected and enterobacteria species were identified using the API 20 E system and by ELISA using anti-enterobacteria IgA. The results showed reduction in the prevalence of enterobacteria, but no significant changes in enterobacterial counts (log CFU/mL; p = 0.3457). The species most frequently isolated were Enterobacter cloacae and Klebsiella oxytoca, both before and after probiotic consumption. No significant changes were observed in anti-enterobacteria IgA levels. In conclusion, probiotic consumption had some influence on enterobacterial presence in the oral cavity, but did not affect enterobacterial counts or the specific immune secretory response against them.

Patogenia de las citopenias autoinmunes primarias / Primary autoimmune cytopenias

Las enfermedades autoinmunes son trastornos secundarios a una des regulación del sistema inmune; éste pierde la capacidad de autotolerancia, y produce un daño crónico, continuo y progresivo. Son patologías muy diversas y pueden llegar a afectar hasta el 5 por ciento de la población. Pueden ser clasificadas en sistémicas u órgano-especificas, dependiendo si el antígeno reconocido es exclusivo del tejido target. A este grupo de enfermedades corresponden las citopenias autoinmunes, condiciones que se caracterizan por disminución del recuento de glóbulos rojos, plaquetas, leucocitos o la mezcla de ellos. Si bien los mecanismos patogénicos que participan en producción de cada una de ellas son similares, cada la tiene características que la hacen particularmente interesante. De esta manera tenemos que la anemia hemolítica autoinmune (AHAI) en un síndrome clínico que se produce debido a la disminución de glóbulos rojos secundaria a una destrucción exagerada de ellos, mediada por la alteración de la respuesta inmune, en la que los antígenos de la membrana de estas células son reconocidos como extraños por nuestro sistema inmune. La clasificación de la AHA/ está dada por la temperatura óptima de unión entre el anticuerpo y la membrana del glóbulo rojo; de esta forma, tenemos tres grandes grupos: por Anticuerpos calientes (WAHA), por Anticuerpos fríos (CAHA) y Mixtas (mediadas por anticuerpos calientes y frios). El diagnóstico de AHAl se confirma con la demostración de anticuerpos y/o proteínas del complemento en la superficie de los eritrocitos; entre ellos encontramos: Coombs directo y Coombs indirecto, test de Coombs recto anti-lgM , búsqueda de C3b en la membrana del glóbulo rojo y finalmente la prueba cualitativa de Donath-Landsteine Las trombopenias autoinmunes corresponden a un grupo de desórdenes que se caracterizan por tener un recuento plaquetario bajo 150.000, mediado por una alteración del sistema inmune. (3.14) La trombocitopenia autoinmune puede ser...

Autoimmune diseases are disorders secondary to a deregulation of the immune system, which loses the capacity for self-tolerance, resulting in chronic, continuous and progressive damage. These pathologies are very diverse and affect up to 5 percent of the population. They can be classified into systemic or organ-specific, depending on whether the recognized antigen is unique to the target tissue. Autoimmune cytopenias belong to this group of diseases and are characterized by a decreased count of red blood cells, platelets, leukocytes, or a mix of these. While the pathogenic mechanisms involved in the production of each are similar, each has features that make it particularly interesting. We have autoimmune hemolytic anemia (AlHA), which is a clinical syndrome that occurs due to a decreased number of red blood cells secondary to an exaggerated destruction of the same, mediated by an alteration of the immune response, in which the membrane antigens of these cells are recognized as foreign by our immune system. The classification of AIHA is given by the optimum bond temperature between the antibody and red blood cell membrane. There are 3 main groups: warm antibodies(WAHA), Cold antibodies (CAHA) and mixed (mediated by hot and cold antibodies). AIHA diagnosis is confirmed with the demonstration of antibodies and/or complement proteins on the surface of red blood cells, among these are the direct and indirect Coombs test, direct anti-IgM Coombs test, the search for C3b in the membrane of the red cell and, finally, the qualitative Donath-Landsteiner test. Autoimmune thrombocytopenia isassociated with a group of disorders characterized by a platelet count under 150,000, mediated by an alteration of the immune system.(3-14) Autoimmune thrombocytopenia can be classified as primary or secondary, and these, in turn, into acute and chronic, depending on whether they last 6 months or more, respectively. Antibodies that react against the glycoproteins of the plate...

Hiperatividade de neutrófilos na periodontite: ativação de receptores Fcy / Neutrophils´ hyperactivity in periodontitis: activation of Fcy receptors

A destruição dos tecidos periodontais está associada a liberação de enzimas proteolíticas e espécies reativas de oxigênio, predominantemente de neutrófilos ativados por receptores Fcy. O objetivo do estudo foi revisar a literatura sobre a importância do receptor Fcy na hiperativação de neutrófilos e, consequentemente, na suscetibilidade do hospedeiro a periodontite. A ativação do neutrófilo requer a ligação dos receptores Fcy por moléculas de Ig que, através de mediadores intracelulares, resulta em eventos de transdução de sinal, incluindo a transcrição de genes codificadores de citocinas, enzimas microbicidas e mobilização do citoesqueleto, levando a fagocitose, exocitose de grânulos e migração celular. Na hiperatividade do neutrófilo, suas funções estão exacerbadas. Uma explicação plausível para essa hiperatividade vem da ativação do receptor Fcy visto que os mesmos respondem de forma distinta a diferentes subclasses de IgG, dependendo: (1) de sua afinidade a estes e da atividade específica de cada categoria do receptor Fcy; (2) pela expressão do receptor Fcy pelas células; e/ou (3) da presença de polimorfismo do receptor Fcy. Sendo assim, podemos concluir que a destruição tecidual no indivíduo portador de periodontite pode estar relacionada a uma hiperatividade de neutrófilos quando ativados por IgG 1 e 2 através dos seus receptores FcαRII e III. Isto se dá principalmente nos casos de polimorfismo para FcαR II a 131, e em meio às altas concentrações de elastase, possibilitando ao FcαR maior afinidade ao ligante, independente dos patógenos periodontais Aa e Pg e do diagnóstico para periodontite ser agressiva ou crônica.

The destruction of periodontal tissue is associated with the release of proteolytic enzymes and reactive oxygenspecies, predominantly by Fcγ activated neutrophils. The aim was to review the literature about the importance of Fcy receptors in the hyperactivation of neutrophils and thus, in the susceptibility of the host in periodontitis. The activation of neutrophil requires Fcy receptor (FcγR) binding to Ig molecules that, through intracellular mediators, results in signal transduction events, including the transcription of genes for cytokines, microbicides enzymes and mobilization of the cytoskeleton, leading to phagocytosis, exocytosis of granules and cell migration. During neutrophilhyperactivity, such functions are exacerbated. A plausible explanation this hyperactivity comes from the FcγR, since they respond differently to different subclasses of IgG. It depends on: (1) its affinity to the receptors and tothe specific activity of each category of FcγR, (2) the expression of the FcγR in cells, and/or (3) polymorphisms forFcγR. Therefore, we concluded that tissue destruction in individuals with periodontitis may be related to a hyperactivity of neutrophils when activated by IgG 1 and 2 through its receptors FcγR II and III. This happens especially in cases of polymorphism for FcγR IIa 131, but also the presence of high concentrations of elastase, which allows a greatest affinity to the FcγR ligand, regardless the presence of periodontal pathogens Aa and Pg, and the specificity of the diagnostics to aggressive or chronic periodontitis.

Detection and Identification of the Spotted Fever Group Rickettsial Agents from Haemaphysalis Ticks in Jeju Island, Korea

This study investigated the presence of nucleic acids of various Rickettsial agents in ticks collected in Jeju Island, Korea from June 2007 to August 2008, through the nested polymerase chain reaction (PCR) and sequencing analysis of partial citrate synthase (gltA), Rickettsial outer membrane protein B (ompB), and 17-kDa genes. Examination of the 1,584 ticks showed that the subspecies distribution of Haemaphysalis longicornis was 99.81% (n=1,581) and H. flava was 0.19% (n=3). A total 224 out of 250 pools from one to 15 ticks were found to be positive in ompB-PCR assay (minimal infection rate 141 ticks/1,000 tested). From the positive samples, 26 were analyzed by gltA- and 17-kDa-PCR assays. The nucleotide sequences of the ompB- and gltA-PCR products showed a high degree of similarity with those of the Rickettsia japonica (98.7~99.2% and 98.7~99.3%, n=25) and R. monacensis (99% and 99.7%, n=1). However, analysis of the nucleotide sequences of the 17-kDa-PCR amplicons showed that the sequences of the 25 PCR amplicons were more close to R. marmionii (99.4~100%) than R. japonica (98.6~99.1%). These findings suggest that various rickettsial diseases could be transmitted via the bite of tick vectors in Jeju Island, Korea.

Intravenous Anti-D immunoglobulin treatment of adult chronic immune thrombocytopenic purpura (ITP) / 대한내과학회지

BACKGROUND/AIMS: Immune thrombocytopenic purpura (ITP) is an autoimmune disease that is mediated by anti-platelet antibodies. Based on the pathogenesis of ITP we evaluated the efficacy of intravenous anti-D immunoglobulin for adult chronic ITP. METHODS: Fourteen patients (4 without splenectomy and 10 with splenectomy) with refractory chronic ITP were treated with 50-70 microgram/kg of intravenous anti-D immunoglobulin only once. Treatment effects were evaluated by measuring the platelet counts and hemoglobin levels. RESULTS: Five patients (36%) showed a response; improvement in the platelet count lasted for on average 7 days (range: 2~24 days). There were no serious adverse effects. CONCLUSION: Anti-D immunoglobulin, which is associated with an Fc receptor blockade, appeared to be safe and effective for the treatment of adults with chronic ITP. Further studies are needed to confirm these findings and define further potentially effective treatment protocols with intravenous anti-D immunoglobulin.

Receptores Fcy y autoinmunidad / Fc receptors and autoimmunity

Los receptores Fc, miembros de la superfamilia de las inmunoglobulinas, participan en fenómenos inflamatorios comoanti-inflamatorios, influyendo sobre la inmunidad innata y adquirida. Factores ambientales y genéticos afectan su expresión. Los receptores Fc participan en el desarrollo de autoinmunidad y otras patologías como cáncer y enfermedades infecciosas. En autoinmunidad cumplen un papel protagónico, ya que controlan una serie de funciones inmunológicas que incluyen reacciones mediadas por complejos inmunes, liberación de citoquinas, lisis celular dependiente de complemento, apoptosis, degranulación de mastocitos, endocitosis y potenciación de la presentación antigénica clase I y clase II. La deficiencia de FcgRIIb está asociada con una susceptibilidad a desarrollar enfermedades autoinmunes. Igualmente, el polimorfismo de los genes para estos receptores se asocia a varias enfermedades autoinmunes. En el presente artículo se revisan las principales funciones de los receptores Fc, su polimorfismo genético y su implicación clínica, en particular en enfermedades autoinmunes.

Caracterização da função dos recepetores Fc de imunoglobulinas nas bacteremias / Characterization of immunoglobulin Fc receptors functions in bacteremias

Este trabalho descreve um papel importante do FcRγII na apoptose de linfócitos B em sepse. Nossos resultados demonstram, ainda, que animais sépticos deficientes em cadeia gamma apresentam menor mortalidade, menores valores de TNFα e de células inflamatórias, assim como um aumento na fagocitose de E. coli. Culturas dos camundongos γ-KO revelaram flora polimicrobiana, ao contrário da forte predominância de E. coli e do maior número total de bactérias, encontrado nos camundongos selvagens. A cadeia gamma é um alvo potencial no tratamento de sepse / This work describes an important role of FcRII in B lymphocytes apoptosis, during serious bacterial infections. Our results showed, moreover, that -chain deficient septic mice have increased survival, diminished TNF levels and cells recruitment, as well as a surprising increase in E. coli phagocytosis. Cultures from -KO mice revealed a polymicrobial flora, in opposite to the strong predominance of E. coli and the increased total bacteria count found for wild-type mice. Gamma-chain is as a potential target for sepsis treatment...

Effect of Inositol-phosphatase on Fc Receptor-mediated Phagocytosis of Macrophages

BACKGROUND: Fc receptor-mediated phagocytosis is a complex process involving the activation of kinases and phosphatases. FcgammaRIIB has been known to transduces inhibitory signals through an immunoreceptor tyrosine-based inhibitory motif (ITIM) in cytoplasmic domains. In this study, we examined the involvement of inositol-phosphatase in the Fc receptor-mediated phagocytosis. METHODS: J774 cells were infected using vaccinia viral vector containing SH2 domain-containing inositol-phosphatase (SHIP) cDNA and stimulated with the sensitized sheep red blood cells. RESULTS: Stimulation of J774 cells induced the tyrosine phosphorylation of SHIP which was maximal at 5 minutes. Phosphatidylinositol-3 (PI-3) kinase inhibitor (wortmannin) inhibits J774 cell phagocytosis of sensitized sheep red blood cells in a dose-dependent manner. Heterologious expression of SHIP in J774 cells inhibits phagocytosis of sensitized sheep red blood cells in a dose-dependency manner, but catalytically dead mutants of SHIP has no effect on phagocytosis. CONCLUSION: These results strongly suggest that the active signals mediated by PI-3 kinase are opposed by inhibitory signals through SHIP in the regulation of Fc receptor-mediated phagocytosis.