Fc gamma receptor IIIa polymorphism is not associated with susceptibility to systemic lupus erythematosus in Brazilian patients / Polimorfismo do receptor Fc gama IIIa não está associado à susceptibilidade ao lúpus eritematoso sistêmico em pacientes brasileiros

ABSTRACT We evaluated the possible association between FCGR3A V/F (158) polymorphism and SLE susceptibility and clinical phenotype in 305 sequentially retrieved SLE patients and 300 healthy controls from the southeastern part of Brazil by allele-specific polymerase chain reaction. Our results showed no association between FCGR3A 158V/F alleles and susceptibility to SLE in this series of patients albeit the heterozygous genotype was strongly associated with the disease.

RESUMO Avaliou-se a possível associação entre o polimorfismo FCGR3A V/F (158) e a suscetibilidade e o fenótipo clínico do lúpus eritematoso sistêmico (LES) em 305 pacientes com LES admitidos sequencialmente e 300 controles saudáveis da Região Sudeste do Brasil por reação em cadeia da polimerase alelo-específica. Os resultados do presente estudo mostraram não haver associação entre os alelos FCGR3A 158 V/F e a suscetibilidade ao LES nessa série de pacientes, ainda que o genótipo heterozigoto tenha sido fortemente associado à doença.

Potential biomarkers for the clinical prognosis of severe dengue

Currently, several assays can confirm acute dengue infection at the point-of-care. However, none of these assays can predict the severity of the disease symptoms. A prognosis test that predicts the likelihood of a dengue patient to develop a severe form of the disease could permit more efficient patient triage and treatment. We hypothesise that mRNA expression of apoptosis and innate immune response-related genes will be differentially regulated during the early stages of dengue and might predict the clinical outcome. Aiming to identify biomarkers for dengue prognosis, we extracted mRNA from the peripheral blood mononuclear cells of mild and severe dengue patients during the febrile stage of the disease to measure the expression levels of selected genes by quantitative polymerase chain reaction. The selected candidate biomarkers were previously identified by our group as differentially expressed in microarray studies. We verified that the mRNA coding for CFD, MAGED1, PSMB9, PRDX4 and FCGR3B were differentially expressed between patients who developed clinical symptoms associated with the mild type of dengue and patients who showed clinical symptoms associated with severe dengue. We suggest that this gene expression panel could putatively serve as biomarkers for the clinical prognosis of dengue haemorrhagic fever.

Targeted resequencing of candidate genes reveals novel variants associated with severe Behcet's uveitis

Behcet's disease (BD) is a chronic systemic inflammatory disorder characterized by four major manifestations: recurrent uveitis, oral and genital ulcers and skin lesions. To identify some pathogenic variants associated with severe Behcet's uveitis, we used targeted and massively parallel sequencing methods to explore the genetic diversity of target regions. A solution-based target enrichment kit was designed to capture whole-exonic regions of 132 candidate genes. Using a multiplexing strategy, 32 samples from patients with a severe type of Behcet's uveitis were sequenced with a Genome Analyzer IIx. We compared the frequency of each variant with that of 59 normal Korean controls, and selected five rare and eight common single-nucleotide variants as the candidates for a replication study. The selected variants were genotyped in 61 cases and 320 controls and, as a result, two rare and seven common variants showed significant associations with severe Behcet's uveitis (P<0.05). Some of these, including rs199955684 in KIR3DL3, rs1801133 in MTHFR, rs1051790 in MICA and rs1051456 in KIR2DL4, were predicted to be damaging by either the PolyPhen-2 or SIFT prediction program. Variants on FCGR3A (rs396991) and ICAM1 (rs5498) have been previously reported as susceptibility loci of this disease, and those on IFNAR1, MTFHR and MICA also replicated the previous reports at the gene level. The KIR3DL3 and KIR2DL4 genes are novel susceptibility genes that have not been reported in association with BD. In conclusion, this study showed that target enrichment and next-generation sequencing technologies can provide valuable information on the genetic predisposition for Behcet's uveitis.

Frequency of FCGR3B Alleles in Thai Blood Donors

BACKGROUND: Human neutrophil antigens (HNAs) are involved in autoimmune and alloimmune neutropenia and transfusion-related acute lung injury. The HNA-1 system is important in immunogenetics, and allele frequencies have been described in different populations. This study investigated the frequency of FCGR3B alleles encoding HNA-1a, HNA-1b, and HNA-1c among Thai blood donors and compared these frequencies with those previously reported for other populations. METHODS: Eight hundred DNA samples obtained from unrelated healthy blood donors at the National Blood Centre, Thai Red Cross Society, Bangkok, and the Blood Bank, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand, were included. Samples were simultaneously typed for each FCGR3B allele using an in-house polymerase chain reaction with sequence-specific primer (PCR-SSP) technique. RESULTS: The frequencies of FCGR3B*1, FCGR3B*2, and FCGR3B*3 alleles in central Thai blood donors were 0.548, 0.452, and 0.004, respectively; only FCGR3B*1 and FCGR3B*2 alleles were found in northern Thai blood donors (0.68 and 0.32, respectively). Compared with other Asian populations, central Thais had higher frequencies of the FCGR3B*2 allele (P<0.001), while the frequencies of the FCGR3B*1 and FCGR3B*2 alleles in northern Thais were similar to those previously reported in Taiwanese and Japanese populations. In contrast, the frequencies of the FCGR3B*1 and FCGR3B*2 alleles in the northern Thai population were statistically different from those observed in central Thai, Korean, German, and Turkish populations. CONCLUSIONS: FCGR3B allele frequencies were significantly different between central and northern Thai blood donors. Our in-house PCR-SSP method is a simple, cost-effective, and convenient method for FCGR3B allele detection.

Nuevas evidencias en la susceptibilidad a la infección por dengue asociadas al polimorfismo HH del receptor FcgRIIa / New evidence in the susceptibility to dengue infection associated to HH polymorphism of FcgRlla receptor

Introducción: las variantes polimórficas del receptor FcgR IIa han sido asociadas con la susceptibilidad a padecer diferentes enfermedades infecciosas. Recientemente se reportó la asociación entre el polimorfismo de este receptor y la susceptibilidad a padecer la fiebre hemorrágica por dengue. Objetivos: explorar si la asociación a la susceptibilidad o protección de las variantes homocigóticas del receptor, pudieran estar relacionadas además, con los títulos de IgG y la exposición a diferente número de infecciones. Métodos: se hizo un estudio de tipo analítico retrospectivo a individuos infectados por virus dengue 4 en Ciudad de La Habana durante la epidemia de 2006, que se contactaron en 2008. Se reclutó un total de 97 individuos, de los cuales 68 habían padecido fiebre dengue y 29 fiebre hemorrágica de dengue.Se les extrajo una muestra de 10 mL de sangre total en anticoagulante que se empleó en el aislamiento de ADN. Se determinó el polimorfismo genético del receptor FcgRIIa, los títulos de anticuerpos totales IgG anti-dengue y el antecedente de infección por dengue. Resultados: se evidenció, de modo interesante, una relación directamente proporcional y muy significativa (p< 0,0001) entre los altos títulos de IgG anti-dengue con el número de infecciones padecidas. Este comportamiento fue característico en los individuos con la variante homocigótica HH. Conclusiones: al parecer, en aquellos individuos con polimorfismo para el receptor FcgRIIa-H/H podría haber una tendencia a la no eliminación de los anticuerpos IgG a través del FcgRIIa, la cual está asociada con el número de infecciones.

Introduction: polymorphic variants of FcgRIIa receptor have been associated to susceptibility to develop several infectious diseases. The relationship between the polymorphism of this receptor and the susceptibility to dengue hemorrhagic fever was recently reported. Objectives: to explore whether the association of the homocygotic variants of the receptor to susceptibility to or protection from a disease could be also related with the IgG antibody titters and the exposure to a number of infections. Methods: a retrospective analytical study was performed on individuals who had been infected with the dengue virus 4 during the 2006 epidemic in the City of Havana and were tracked down in 2008. A total number of 97 individuals were recruited of whom 68 had suffered dengue fever and 29 had had dengue hemorrhagic fever. A 10 mL blood sample was taken from each of them and then placed in EDTA anticoagulant for DNA isolation and 5ml placed in dry tubes to obtain serum. The genetic polymorphism of FcgRlla receptor, the total anti-dengue IgG antibody titers and the antecedent of dengue infection were determined. Results: it was interesting to note that there was very significant direct relation (p< 0.0001) between high anti-dengue IgG antibodies titers and the number of infections suffered by these people. This behaviour was present in those individuals with the HH homocygotic variant. Conclusion: it seems that those individuals with polymorphism in FCgRlla-H/H receptor would tend to non-elimination of IgG antibodies through this receptor, which is associated to the number of infections suffered by the individual.

Fc γ R IIB gene polymorphisms in Indian systemic lupus erythematosus (SLE) patients.

Background & objectives: Receptors for the Fc fragment of immunoglobulin G (Fc γ Rs) represent the link between humoral and cellular immune responses. Polymorphisms in Fc γ Rs have been identified as genetic factors influencing susceptibility to various autoimmune diseases. This study was aimed to identify Fc γ R IIB genotypes in Indian systemic lupus erythematosus (SLE) patients and to correlate these with clinical presentation and autoantibody profile. Methods: Eighty consecutive clinically diagnosed SLE patients were included. SLE patients were classified according to the American College of Rheumatology (ACR) criteria. Disease activity was assessed by Systemic Lupus Erythematosus Disease Activity Index (SLEDAI). PCR-RFLP method was used to detect Fc γ R IIB polymorphism. Results: Of the 80 SLE patients, 53 were LN and 27 were SLE without nephritis. The mean SLEDAI score at evaluation was 6.5 ± 5.8. Among SLE patients Fc γ R IIB genotype frequency was 61.2 per cent for Ile/Thr, 20.0 per cent for Thr/Thr and 18.8 per cent for Ile/Ile as compared to 65, 12.5 and 22.5 per cent respectively among normal population. There was no significant difference for Fc γ R IIB genotypes between SLE and normals. The allele frequency for Thr allele in SLE patients was slightly higher (0.51) than in normals (0.45). Thr allele frequency in LN patients was slightly higher (0.53) than in SLE patients without nephritis (0.49). Though a higher percentages of symptoms like renal manifestations (81.3%), arthritis (62.5%) and oral ulcer (56.3%) were noted in patients with Thr/Thr genotypes, no significant difference was noted when these patients were compared with Ile/Ile and Ile/Thr genotypes. Interpretation & conclusions: The findings of this study indicate towards an involvement of Thr allele with SLE disease severity and clinical presentation in Indian SLE patients. Future study on a large sample is needed to support this finding to understand the association of Fc γ R IIB 232Thr/Thr genotype as a susceptibility factor in SLE.

Variant FCGR3 genes: transcription and possible origins.

The Fc receptors for human immunoglobulin G (FcgammaR) IIIb are encoded by genes clustered on the long arm of chromosome 1 (band q21 --> 24) and exhibit allelic polymorphisms. Several rare FCGR3B sequences were identified in both white and black donors. However, the origins of these genomic variants are unknown and their transcription has not yet been investigated. Blood from a donor with known FCGR3 variants was used to extract DNA from peripheral blood CD34+ cells, CD19+ B-cells, neutrophils and buccal cells, after which FCGR3 gene sequencing was performed. Additionally, RNA samples from 5 Caucasian individuals containing known variant FCGR3 genes were reverse-transcribed to cDNA and the FCGR3 genes were sequenced. Our results showed that the frequencies of variant clones were higher in B-cell preparations than in CD34+ hematopoietic progenitor cells from peripheral blood and neutrophils. Very high variant frequencies were found in buccal cell-derived clones. Variant cDNA sequences were identified in three of five individuals with known FCGR3 variants. We conclude that FCGR3 gene variants are differentially transcribed between cell types and tissues, increasing the likelihood of the presence of variant FcgammaRIII receptors on the cell surface. The significance of the high number of variant clones in buccal cells, however, is unclear.

Distribution of variant genotypes of Fc gamma receptor IIIa in healthy Chinese population of Zhengzhou City / 华中科技大学学报（医学）（英德文版）

To investigate the distribution of variant genotypes of Fc gamma receptor IIIa (Fc gamma R IIIa) in healthy Chinese population of Zhengzhou city, genomic DNA was extracted from peripheral blood of healthy donators. The genotypes of Fc gamma R IIIa-158 were determined by nested polymerase chain reaction (PCR) in 137 healthy people in Zhengzhou city. The results showed that frequencies of variant genotypes FF, VV and VF were 42.3%, 48.9% and 8.8% respectively. The distribution of Fc gamma R IIIa-158 in healthy Chinese population of Zhengzhou city was polymorphic and different from that of African Americans (AA) and Caucasian Americans (CA).

Association Between FcgammaR IIa and IIIa Polymorphism and Clinical Manifestations in Korean Patients with Adult-Onset Still's Disease

High-dose intravenous immunoglobulins alter the disease activity of adult-onset Still's disease (AOSD). Because activation status of FcgammaR is possibly dependent on their genetic polymorphisms, we investigated whether the polymorphisms of FcgammaR IIa and IIIa are risk factors, and affect the clinical features of AOSD. Genomic DNA was extracted from 36 patients and from 197 healthy controls. Polymerase chain reaction for FcgammaR IIa and IIIa using the allele-specific primers and direct sequencing of FcgammaR IIIa polymorphic site were performed. The frequencies of FcgammaR IIa/IIIa genotype between patients with AOSD and controls were not different. The allelic frequencies of FcgammaR IIa/IIIa between patients with AOSD and controls were not different, either. However, the FcgammaR IIa-R/R131 genotype was associated with a higher concentration of hemoglobin (p=0.04) and stable liver function (p=0.009) than the other genotypes. The FcgammaR IIIa-F/F176 genotype was associated with significantly lower titers of serum ferritin (p=0.025), and higher serum albumin (p=0.037) and cholesterol (p=0.014) concentrations than the other genotypes. This study suggest that the FcgammaR IIa and IIIa polymorphisms might not be genetic risk factors for AOSD in Korean, but contribute to the activity of disease. FcgammaR IIa-R/R131 and IIIa-F/F176 genotypes, low-binding genotypes for IgG2a and G1, may have more protective effects in acute stage of the disease than the other genotypes.

IgG binding and expression of its receptor in rat intestine during postnatal development.

The binding of 125I labelled IgG to the microvillus membranes (MVM) has been studied during postnatal development of rat intestine. The levels of mRNA encoding IgG receptor were also analyzed by liquid hybridization under these conditions. The IgG binding to MVM reached maximum levels by day 12 and showed a gradual decline upon weaning. The FcRn mRNA was markedly low in adult rats and was maximum during second week of postnatal development. Administration of cortisone or thyroxine to suckling rats, induced precocious decline of both IgG binding and the receptor expression. However, insulin administration did not affect the receptor expression. Scatchard analysis of IgG binding to MVM in cortisone injected pups revealed that the observed inhibition in IgG binding was a consequence of a decrease, both in the affinity constant (-Ka) as well as in the number of receptor sites (n) while thyroxine administration caused a reduction in the number of receptor sites from 2.29 in control to 1.14 nmoles/mg protein in thyroxine injected pups. These observations indicate that expression of IgG receptor during postnatal development is a hormone regulated process.