Allelic polymorphisms of human fcgamma receptor IIa and Fcgamma receptor IIIb among distinct groups in Brazil

FCGR Genetic Variation in Two Populations From Ecuador Highlands-Extensive Copy-Number Variation, Distinctive Distribution of Functional Polymorphisms, and a Novel, Locally Common, Chimeric FCGR3B/A (CD16B/A) Gene

Fcγ receptors (FcγR), cell-surface glycoproteins that bind antigen-IgG complexes, control both humoral and cellular immune responses. The FCGR locus on chromosome 1q23.3 comprises five homologous genes encoding low-affinity FcγRII and FcγRIII, and displays functionally relevant polymorphism that impacts on human health. Recurrent events of non-allelic homologous recombination across the FCGR locus result in copy-number variation of ~82.5 kbp-long fragments known as copy-number regions (CNR). Here, we characterize a recently described deletion that we name CNR5, which results in loss of FCGR3A, FCGR3B, and FCGR2C, and generation of a recombinant FCGR3B/A gene. We show that the CNR5 recombination spot lies at the beginning of the third FCGR3 intron. Although the FCGR3B/A-encoded hybrid protein CD16B/A reaches the plasma membrane in transfected cells, its possible natural expression, predictably restricted to neutrophils, could not be demonstrated in resting or interferon γ-stimulated cells. As the CNR5-deletion was originally described in an Ecuadorian family from Llano Grande (an indigenous community in North-Eastern Quito), we characterized the FCGR genetic variation in two populations from the highlands of Ecuador. Our results reveal that CNR5-deletion is relatively frequent in Llano Grande (5 carriers out of 36 donors). Furthermore, we found a high frequency of two strong-phagocytosis variants: the FCGR3B-NA1 haplotype and the CNR1 duplication, which translates into an increased FCGR3B and FCGR2C copy-number. CNR1 duplication was particularly increased in Llano Grande, 77.8% of the studied sample carrying at least one such duplication. In contrast, an extended haplotype CD16A-176V – CD32C-ORF+2B.2 – CD32B-2B.4 including strong activating and inhibitory FcγR variants was absent in Llano Grande and found at a low frequency (8.6%) in Ecuador highlands. This particular distribution of FCGR polymorphism, possibly a result of selective pressures, further confirms the importance of a comprehensive, joint analysis of all genetic variations in the locus and warrants additional studies on their putative clinical impact. In conclusion, our study confirms important ethnic variation at the FCGR locus; it shows a distinctive FCGR polymorphism distribution in Ecuador highlands; provides a molecular characterization of a novel CNR5-deletion associated with CD16A and CD16B deficiency; and confirms its presence in that population.

Peripheral neutrophil phenotypes during management of periodontitis

BACKGROUND AND OBJECTIVES

Neutrophils are emerging as a key player in periodontal pathogenesis. The surface expression of cellular markers enables functional phenotyping of neutrophils which have distinct roles in disease states. This study aimed to evaluate the effect of periodontal management on neutrophil phenotypes in peripheral blood in periodontitis patients over one year.

MATERIALS AND METHODS

Peripheral blood and the periodontal parameters, mean probing depth and percentage of sites with bleeding on probing (%BOP), were collected from 40 healthy controls and 54 periodontitis patients at baseline and 3-, 6- and 12- months post-treatment. Flow cytometry was used to identify CD11b⁺ , CD16b⁺ , CD62L^- and CD66b⁺ expression on neutrophils, neutrophil maturation stages as promyelocytes (CD11b^- CD16b^- ), metamyelocytes (CD11b⁺ CD16b^- ) and mature neutrophils (CD11b⁺ CD16b⁺ ), and suppressive neutrophil phenotype as bands (CD16^dim CD62L^bright ), normal neutrophils (CD16^bright CD62L^bright ) and suppressive neutrophils (CD16^bright CD62L^dim ).

RESULTS

CD62L^- expression decreased with treatment. No differences were observed in neutrophil maturation stages in health or disease upon treatment. Suppressive and normal neutrophils showed a reciprocal relationship, where suppressive neutrophils decreased with treatment and normal neutrophils increased with treatment. In addition, %BOP was associated with suppressive neutrophils.

CONCLUSION

This study demonstrates that management of periodontitis significantly modifies distinct neutrophil phenotypes in peripheral blood. Suppressive neutrophils may play a role in the pathogenesis of periodontitis. However, their exact role is unclear and requires further investigation.

Fc-gamma IIIa-V158F receptor polymorphism contributes to the severity of Guillain-Barré syndrome

Objective

Guillain‐Barré syndrome (GBS) is a rare, life‐threatening disorder of the peripheral nervous system. Immunoglobulin G Fc‐gamma receptors (FcγRs) mediate and regulate diverse effector functions and are involved in the pathogenesis of GBS. We investigated whether the FcγR polymorphisms FcγRIIa H/R131 (rs1801274), FcγRIIIa V/F158 (rs396991), and FcγRIIIb NA1/NA2, and their haplotype patterns affect the affinity of IgG‐FcγR interactivity and influence GBS susceptibility and severity.

Methods

We determined FcγR polymorphisms in 303 patients with GBS and 302 ethnically matched healthy individuals from Bangladesh by allele‐specific polymerase chain reaction. Pairwise linkage disequilibrium and haplotype patterns were analyzed based on D ´statistics and the genotype package of R statistics, respectively. Logistic regression analysis and Fisher’s exact test with corrected P (Pc) values were employed for statistical comparisons.

Results

FcγRIIIa‐V158F was associated with the severe form of GBS compared to the mild form (P = 0.005, OR = 2.24, 95% CI = 1.28–3.91; Pc = 0.015); however, FcγR genotypes and haplotype patterns did not show any association with GBS susceptibility compared to healthy controls. FcγRIIIa‐V/V158 and FcγRIIIb‐NA2/2 were associated with recent Campylobacter jejuni infection (P ≤ 0.001, OR = 0.36, 95% CI = 0.23–0.56; Pc ≤ 0.003 and P = 0.004, OR = 1.70, 95% CI = 1.18–2.44; Pc ≤ 0.012, respectively). Haplotype 1 (FcγRIIa‐H131R‐ FcγRIIIa‐V158F‐ FcγRIIIb‐NA1/2) and the FcγRIIIb‐NA2/2 genotype were more prevalent among anti‐GM1 antibody‐positive patients (P = 0.031, OR = 9.61, 95% CI = 1.24–74.77, Pc = 0.279; P = 0.027, OR = 1.62, 95% CI = 1.06–2.5, Pc = 0.081, respectively).

Interpretation

FcγR polymorphisms and haplotypes are not associated with susceptibility to GBS, though the FcγRIIIa‐V158F genotype is associated with the severity of GBS.

Fc gamma receptor IIIb polymorphism and systemic lupus erythematosus: association with disease susceptibility and identification of a novel FCGR3B*01 variant

OBJECTIVE

The objective of this study was to evaluate the association between Fc gamma receptor IIIb polymorphism and susceptibility to systemic lupus erythematosus and clinical traits of the disease.

METHODS

Genomic DNA was obtained from 303 consecutive systemic lupus erythematosus patients and 300 healthy blood donors from the southeastern region of Brazil. The polymorphic region of the FCGR3B gene was sequenced and the alleles FCGR3B*01, FCGR3B*02 and FCGR3B*03 were analyzed.

RESULTS

The FCGR3B*01 allele was more frequent in systemic lupus erythematosus patients (43.1%) while the FCGR3B*02 allele prevailed among controls (63.7%) (P = 0.001). The FCGR3B*03 allele was found equally in both groups. The FCGR3B*01/*01 (20.7%) and FCGR3B*01/*02 (41.1%) genotypes were more frequent among systemic lupus erythematosus patients (P = 0.028 and P = 0.012, respectively) while the FCGR3B*02/*02 genotype was more frequent in controls (45.5%) (P < 0.001). One variant of the FCGR3B*01 allele previously described in Germany was found in only one control. A new variant of the FCGR3B*01 allele with two substitutions (A227G/G277A) was found in one control. Three variants of the FCGR3B*02 allele previously described in African-Americans, Brazilians, Chinese and Japanese were found in ten 10 patients and two controls. In addition, several single nucleotide polymorphisms at non-polymorphic positions were identified in both patients and controls.

CONCLUSION

Susceptibility to systemic lupus erythematosus was associated with the FCGR3B*01 allele, as well as with the FCGR3B*01/*01 and FCGR3B*01/*02 genotypes. No association was found between FCGR3B genotypes and clinical manifestations, disease severity or the presence of autoantibodies.

Association of FcγRIIa Polymorphism with Clinical Outcome of Dengue Infection: First Insight from Pakistan

Dengue illness has been a major health concern in Pakistan during the last decade. Dengue infection can result in a spectrum of clinically distinct outcomes, ranging from asymptomatic infection to potentially life-threatening forms of dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). A single-nucleotide polymorphism in FcγRIIa (rs1801274) results in altered affinity of the receptor for different subclasses of immunoglobulin G, and is a key player in determining the susceptibility to or protection from severe clinical infection of dengue. In this study, we analyzed the allelic and genotypic distribution of rs1801274 in subjects of Pakistani origin with subclinical dengue infection (n = 40), dengue fever (DF) (n = 40), and DHF/DSS (n = 30). We found that HH homozygotes and heterozygotes were significantly more likely to develop clinical dengue (odds ratio [OR] = 3.21, 95% confidence interval [CI] = 1.29-7.97, P = 0.009), either DF (OR = 2.82, 95% CI = 1.00-7.97, P = 0.045) or DHF/DSS (OR = 3.90, 95% CI = 1.13-13.07, P = 0.024) than the asymptomatic dengue infection. Results of allelic distribution comparisons and logistic regression analysis also supported the same relationship. The results suggest complex nature of interacting factors in determining the course for severe dengue illness.

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.

The Fc receptor polymorphisms and expression of neutrophil activation markers in patients with sickle cell disease from Western India

Objective. Sickle cell disease has variable clinical manifestations. Activation of neutrophils plays an important role in the initiation and propagation of vaso occlusive crises which can be analysed by determining the expression of neutrophil antigens such as CD16, CD32, and CD62L. The common FcγR polymorphisms (FcγRIIA and FcγRIIIB) are considered to influence clinical presentation. This study focuses on distribution of FcγR polymorphisms and their association with neutrophil activity among the patients from western India. Methods. In this paper 127 sickle cell anemia patients and 58 patients with sickle-β-thalassemia (median age 12 ± 8.58 years) with variable clinical phenotypes along with 175 normals were investigated. FcγRs polymorphisms were analysed by RFLP and AS-PCR. Activation of neutrophils was measured by flow cytometry. Results. The genotypic frequency of the H/R genotype of FcγRIIA and the NA1/NA1 genotype of FcγRIIIB was significantly decreased in patients compared to normals (P-0.0074, P-0.0471, resp.). We found a significant difference in the expression of CD32 and CD62L among the patients as against normals. A significantly higher expression of CD32 was seen in the milder patients with the H/H genotype (P-0.0231), whereas the expression of CD16 was higher in severe patients with the NA2/NA2 genotype (P-0.0312). Conclusion. The two FcγR polymorphisms had significant association with variable phenotypes of sickle cell disease. The expression of CD62L decreased in our patients indicating activation of neutrophils.

Analysis of Fcgamma receptor IIa (cd32) gene polymorphism and anti-malarial IgG subclass antibodies to asexual blood-stage antigen of Plasmodium falciparum in an unstable malaria endemic area of Iran

One of the main host genetic factors involved in inflammation, immune responses and pathogenesis of malaria is FcγRIIa (cd32) gene. A single point mutation at position 131 replace an arginine (R) with a histidine (H) that can affect the affinity of the receptor for human IgG subclasses. This investigation was designed to explore the polymorphisms at FcγRIIa gene in association with both anti-malarial total IgG antibody and IgG subclass profiles to C-terminal region of Plasmodium falciparum merozoite surface protein 1 (PfMSP-1(19)). In this study, 166 infected patients with P. falciparum who are living in a malaria endemic area of Iran were studied using PCR-RFLP and ELISA methods. The results showed that the frequency of FcγRIIa-R/R131, -R/H131 and -H/H131 genotypes was 9.6%, 42.8% and 47.6%, respectively. Level of total IgG to recombinant PfMSP-1(19) antigen showed that there was no difference among the FcγRIIa-R/R131, -R/H131 and -H/H131 groups. With regards to the IgG subclasses, the anti-malarial IgG1 antibodies predominated. Also, there was a significant difference between the frequency of positive responders for anti-PfMSP-1(19) IgG and IgG1 antibodies in P. falciparum-infected individuals with FcγRIIa-R/R131, -R/H131 or -H/H131 genotypes (P<0.05, X(2) test). Regarding to IgG2-PfMSP-1(19) antibody, 27.27% (FcγRIIa-R/R131), 25.71% (FcγRIIa-R/H131) and 22.2% (FcγRIIa-H/H131) of IgG responders showed positive antibody response. Taken together, this study is the first report that exhibits the high frequency of both FcγRIIa-H131H genotypes and H131 allele in the Baluchi ethnic group, which was similar to the Fulani ethnic group. The present results provide additional data to understand the role of FcγRIIa-131 genotypes in the pathogenesis of malaria.

Human neutrophil alloantigen genotype frequencies among blood donors with Turkish and German descent

Antibodies against the human neutrophil antigens (HNA) are able to stimulate transfusion reactions, autoimmune and neonatal neutropenia. The aim of this study was to determine the HNA allele frequencies in the largest ethnic minority group in Germany in comparison with the German population for predicting the risk of alloimmunization and associated transfusion reactions, as well as the risk of developing neonatal neutropenia for the newborn of racial mixed couples. However, there exists no data about HNA genotype distribution in Turkish population. DNA was isolated from blood samples of 119 German and 118 Turkish blood donors and typed them for HNA-1, -3, -4, and -5 by using a commercial polymerase chain reaction kit with sequence-specific primers (SSP-PCR) and compared the HNA genotype distribution of both groups. In German blood donors, the gene frequencies for HNA-1a and HNA-1b were 0.391 and 0.601, for HNA-3a and -3b, 0.744 and 0.256, for HNA-4a and -4b, 0.908 and 0.092, and for HNA-5a and -5bw, 0.731 and 0.269. In Turkish blood donors, we observed 0.420/0.564, 0.737/0.263, 0.881/0.119, and 0.754/0.246 for HNA-1a/1b, -3a/3b, -4a/4b, and -5a/5bw. No statistic significant difference between genotypes in these populations was observed. This study is the first to report HNA gene frequencies in a Turkish population. It showed that there is no difference of HNA genotype in blood donors with Turkish descent in comparison with German blood donors. The alternating transfusion of blood and blood components is no increased risk for developing alloantibodies against HNA antigens. In pregnancy of mixed couples no special screening programs for HNA are necessary.

FCGR3B*03 allele inheritance pattern in Brazilian families and some new variants of gene FCGR3B

BACKGROUND

The FCGR3B gene encoding the FcyRIIIb receptor for immunoglobulin G has three polymorphic forms known as HNA-1a, HNA-1b, and HNA-1c, encoded by the alleles FCGR3B*01, FCGR3B*02, and FCGR3B*03, respectively. It is not clear whether the inheritance of the FCGR3B*03 allele, which encodes the HNA-1c, is linked or not to the other two alleles. The objective of this study was to identify the inheritance pattern of the FCGR3B*03 allele in Brazilians.

STUDY DESIGN AND METHODS

Blood samples from nine families with at least one FCGR3B*03(+) member, totalizing 47 individuals, were studied. The presence of the FCGR3B*01, FCGR3B*02, and FCGR3B*03 alleles was detected by the polymerase chain reaction with sequence-specific priming method, and all DNA samples were sequenced.

RESULTS

In three of the nine studied families, the FCGR3B*03 was passed down with the FCGR3B*02, while in one family the FCGR3B*03 was inherited in linkage with FCGR3B*01. The other families were not informative regarding FCGR3B*03 inheritance. Sequencing showed for the first time one single-nucleotide polymorphism at Position 264 resulting from a simple substitution C→T; three other different substitutions at Position 230, T→A, T→G; and the presence of three nucleotides at Position 230 (T, G, and A). The previously reported variants FCGR3B*01A227G and FCGR3BG330T were also found.

CONCLUSION

In this Brazilian FCGR3B*03(+) group we found that the inheritance of FCGR3B*03 took place by a linkage to FCGR3B*02 or to FCGR3B*01. Linkage of FCGR3B*03 to FCGR3B*02 was the most common. Additionally, we report SNPs that have not been described, suggesting that they might be more common than previously thought.

Immunoglobulin IgG Fc-receptor polymorphisms and HLA class II molecules in Guillain-Barré syndrome

OBJECTIVE

To analyze host genetic factors immunoglobulin G Fc receptors (FcgammaRs) and human leukocyte antigen (HLA) class II in GBS patients.

METHODS

FcgammaRIIA, IIIA and IIIB polymorphisms were studied in 80 each GBS patients and healthy controls by allele specific PCR. HLA class II DRbeta1 and DQbeta1 typing was performed at the two-digit level by PCR in randomly selected 54 GBS patients and 202 controls.

RESULTS

FcgammaRIIA-H/H (56% vs 9%; P < 0.0001) and FcgammaRIIIA-V/V (40% vs 13%; P < 0.0001) genotypes, H131 allele frequencies (0.73 vs 0.26, P < 0.0001) and HLA DQbeta1*060x (OR, 1.96; 95% CI, 1.26-3.04; P < 0.01) were significantly increased in GBS than controls. DRbeta1*0701 alone (OR, 10; 95% CI, 45.90-2.25; P < 0.001) and together with FcgammaRIIA-H/H (OR, 11.03; 95% CI, 2.63-46.20; P < 0.001) was significantly associated with GBS patients having microbiological evidence of recent infection.

CONCLUSIONS

The study indicates that homozygous FcgammaRIIA and FcgammaRIIIA genotypes and FcgammaRIIA H131 allele are associated with GBS. HLA class II molecule DRbeta1*0701 is identified as novel genetic risk factor for development of GBS in patients with preceding infection.

Human neutrophil alloantigen-1a, -1b, -2, -3a and -4a frequencies in Brazilians

Human neutrophil reactive antibodies may cause clinical disorders such as transfusion-related acute lung injury, febrile transfusion reactions, alloimmune neonatal neutropenia, immune neutropenia after stem cell transplantation, refractoriness to granulocyte transfusion, drug-induced neutropenia and autoimmune neutropenia. Using the granulocyte immunofluorescence test by flow cytometry, the phenotypic frequencies of the human neutrophil alloantigens (HNA)-1a, -1b, -2, -3a and -4a were determined in 100 healthy Brazilian persons. Neutrophils were separated from blood samples by sedimentation, centrifugated and incubated with HNA-specific alloantibody plus fluorescein isothiocyanate-labeled F(ab')(2) fragments of anti-human IgG. The results showed that the phenotype frequencies of HNA-1a, -1b, -2a, -3a and -4a were 65%, 83%, 97%, 95% and 94%, respectively. We detected that neutrophils from 17% of Brazilians typed positive only with anti-HNA-1a (HNA-1a/a), 35% only with anti-HNA-1b (HNA-1b/b) and 48% reacted with both antibodies (HNA-1a/b). The frequencies found for HNA-1a and -1b were quite similar to that reported among Africans and American-Africans, but different from those found in Japanese and Chinese. In addition, our data showed that the frequencies of HNA-2, -3a and -4a in Brazilians were comparable with those observed in Caucasians. The determination of HNAs frequencies among populations with distinct racial backgrounds is important not only for anthropological reasons, but also for neonatal typing in suspected cases of alloimmune neutropenia or when patients are severely neutropenic.

Human neutrophil alloantigens systems

Neutrophil alloantigens are involved in a variety of clinical conditions including immune neutropenias, transfusion-related acute lung injury (TRALI), refractoriness to granulocyte transfusions and febrile transfusion reactions. In the last decade, considerable progress has been made in the characterization of the implicated antigens. Currently, seven antigens are assigned to five human neutrophil antigen (HNA) systems. The HNA-1a, HNA-1b and HNA-1c antigens have been identified as polymorphic forms of the neutrophil Fcγ receptor IIIb (CD16b), encoded by three alleles. Recently, the primary structure of the HNA-2a antigen was elucidated and the HNA-2a-bearing glycoprotein was identified as a member of the Ly-6/uPAR superfamily, which has been clustered as CD177. The HNA-3a antigen is located on a 70-95 kDa glycoprotein; however, its molecular basis is still unknown. Finally, the HNA-4a and HNA-5a antigens were found to be caused by single nucleotide mutations in the αM (CD11b) and αL (CD11a) subunits of the leucocyte adhesion molecules (β2 integrins). Molecular and biochemical characterization of neutrophil antigenshave expanded our diagnostic tools by the introduction of genotyping techniques and immunoassays for antibody identification. Further studies in the field of neutrophil immunology will facilitate the prevention and management of transfusion reactions and immune diseases caused by neutrophil antibodies.

HNA-1a, HNA-1b and HNA-1c gene frequencies in Argentineans

Human neutrophil antigens (HNA) are polymorphic structures located in the neutrophil membrane. The neutrophil-specific antigens HNA-1a (NA1), 1b (NA2) and 1c (SH) are well-recognized allotypic forms of FcgammaRIIIb and the most frequent targets of neutrophil alloantibodies. The aim of this study was to determine the gene frequencies of the neutrophil-specific antigens belonging to the HNA-1 system in blood donors and Toba Amerindians from Rosario, Argentina. Two hundred and eighteen unrelated healthy Argentinean blood donors and Toba Amerindians from Rosario were typed for HNA-1a, HNA-1b and HNA-1c using polymerase chain reaction with sequence-specific primers. For the Argentinean blood donors, the HNA-1a and HNA-1b gene frequencies were 0.44 and 0.56 and for the Amerindians Toba were 0.77 and 0.23, respectively. The HNA-1c antigen is present in 4.7% (gene frequency=0.023) of the blood donors but in none of the Amerindian individuals. The present data showed that the HNA-1 allele frequencies in the major population and the Toba Amerindians from Rosario are similar to those described in European and others distant Amerindians populations, respectively.

Human neutrophil alloantigens

OBJECTIVE

This review describes alloantigens currently listed in the human neutrophil alloantigen (HNA) system.

MATERIAL AND METHODS

Review of the literature.

RESULTS

Neutrophil antigens are implicated in a variety of clinical conditions including neonatal immune neutropenia, transfusion-related acute lung injury, refractoriness to granulocyte transfusions, febrile transfusion reactions, immune neutropenia after bone marrow transplantation, autoimmune neutropenia and drug-induced immune neutropenia. Seven antigens have been listed in the HNA system that are assigned to five antigen groups. Six antigens have been characterized biochemically and molecularly so that their primary structure is now known. As shown by regularly performed international granulocyte immunology workshops, a combination of granulocyte agglutination and immunofluorescence tests together with a panel of typed cells is currently the best means of detection.

CONCLUSIONS

Most of the HNA antigens have been well-characterized so that HNA typing as well as the detection of the corresponding antibodies are now reliably possible. This will improve diagnostics of neutrophil antibody-mediated clinical conditions as well as the prevention of transfusion-related acute lung injury.

Rheumatoid peripheral blood phagocytes are primed for activation but have impaired Fc-mediated generation of reactive oxygen species

Significant levels of circulating immune complexes (ICs) containing rheumatoid factors and immunoglobulin G in peripheral blood are a characteristic feature of rheumatoid arthritis (RA). ICs interact through Fcγ receptors (FcγR) to activate phagocytes in numerous inflammatory processes. The high concentration of neutrophils in synovial fluid during active phases of the disease, together with their destructive capacity, pose important questions as to their role in the pathogenesis of RA. Functional defects in RA or control peripheral blood neutrophil FcγRs were examined with a specific FcγR-mediated reactive oxygen species (ROS) assay. Heterologous cross-linking of FcγRIIa and FcγRIIIb on neutrophils resulted in a significantly decreased production of ROS by RA cells compared with controls matched for age and sex. However, expression and homologous ligation of receptors did not differ between these groups. These data suggest that neutrophil priming does occur before emigration into the joint and that blood neutrophils from patients with RA have a functional impairment in cooperative FcγR-mediated ROS generation. This may account for the increased susceptibility to bacterial infection that arises in patients with severe disease.

Gene frequencies of the HNA-4a and -5a neutrophil antigens in Brazilian persons and a new polymerase chain reaction-restriction fragment length polymorphism method for HNA-5a genotyping

BACKGROUND

The HNA-4a (Mart) and HNA-5a (Ond) antigens are polymorphic variants of alpha(M) (CD11b) and alpha(L) (CD11a) subunits of the beta(2)-integrin, and are associated with single nucleotide polymorphisms (SNP) leading to amino acid dimorphisms. HNA-4a has been linked to alloimmune neonatal neutropenia, but the HNA-5a clinical significance is unclear.

STUDY DESIGN AND METHODS

Using a polymerase chain reaction (PCR) with sequence-specific primers, the frequency of HNA-4a among 121 Brazilian blood donors and 114 Amazon Indians was determined. A PCR-restriction fragment length polymorphism (RFLP) method for HNA-5a genotyping was developed, and the gene frequencies of this antigen were determined among 123 blood donors and 114 Indians. To validate the genotyping method, the amplified DNA from six previously obtained samples (two of each genotype) was sequenced.

RESULTS

The HNA-4a (+/+), HNA-4a (+/-), and HNA-4a (-/-) genotype frequencies of blood donors (0.686, 0.273, 0.041) and Indians (1.000, 0.000, 0.000) were different (p < 0.01). The frequencies of HNA-5a (+/+), HNA-5a (+/-), and HNA-5a (-/-) genotypes among blood donors (0.512, 0.399, 0.089) and Indians (0.746, 0.219, 0.035) also differed (p < 0.01). Sequencing demonstrated concordance with PCR-RFLP genotyping in all six evaluated samples.

CONCLUSION

Comparing to another populations, Brazilians present a higher frequency of HNA-4a-negative allele, suggesting that Brazilians would be more susceptible to HNA-4a alloimmunization. Moreover, the distribution of the HNA-4 alleles observed in Amazon Indians is quite similar to that reported among Koreans. Besides that, a new effective and efficient HNA-5a genotyping technique is now available for population studies.

Polymorphism of the Fcgamma receptor IIA and malaria morbidity

Fc receptors (FcRs) are expressed on the surface of all types of cells of the immune system. They bind the Fc portion of immunoglobulin (Ig), thereby bridging specific antigen recognition by antibodies with cellular effector mechanisms. FcγRIIA, one of the three receptors for human IgG, is a low-affinity receptor for monomeric IgG, but binds IgG immune complexes efficiently. FcγRIIA is believed to play a major role in eliciting monocyte- and macrophage-mediated effector responses against blood-stage malaria parasites. A G → A single nucleotide polymorphism, which causes an arginine (R) to be replaced with histidine (H) at position 131, defines two allotypes which difer in their avidity for complexed human IgG₂ and IgG₃. Because FcγRIIA-H131 is the only FcγR allotype which interacts efficiently with human IgG_2, this polymorphism may determine whether parasite-specific IgG₂ may or may not elicit cooperation with cellular imune responses during blood-stage malaria infection. Here, we review data from four published case-control studies describing associations between FcγRIIA R/H131 polymorphism and malaria-related outcomes and discuss possible reasons for some incongruities found in these available results.

Variation in the FcgammaR3B gene among distinct Brazilian populations

The FCGR3B gene codes for the FcgammaR3b receptor, which occurs in three polymorphic forms representing the human neutrophil antigens (HNA)-1a, HNA-1b, and HNA-1c. The alleles that code for these antigens are FCGR3B*1, FCGR3B*2, and FCGR3B*3, respectively. New variants of these alleles have been recently described. In order to study the frequency of these alleles and the occurrence of variant forms, we sequenced part of the FCGR3B gene in 149 individuals belonging to four distinct Brazilian populations, i.e., 60 Amerindians, 30 Whites of European descent, 30 Afro-Brazilians, and 30 Japanese. The FCGR3B*1 allele showed high frequency among Amerindians (0.850), with the value detected representing the highest frequency described thus far for this allele in population studies. Its frequency was 0.660 in the Japanese population studied, a value equal to that observed in Afro-Brazilians (0.600) and higher than that observed in Whites (0.480). The FCGR3B*3 allele was only found among Afro-Brazilians, where it occurred at a frequency of 0.080, which was lower than the frequency observed among Afro-North Americans (0.207) and Ugandans (0.166). Two variant haplotypes were detected among Amerindians and Afro-Brazilians, occurring in six individuals (four Amerindians and two Afro-Brazilians). The variant haplotype FCGR3B*1 A227G, which occurred in homozygosis in two Amerindians and in heterozygosis in two Afro-Brazilians, is described for the first time in the present report. In general, these data reveal variability in the frequency of alleles of the FCGR3B gene compared to other populations of the same genetic background in other regions of the world.

Fc RIIa polymorphism: a susceptibility factor for immune complex-mediated lupus nephritis in Brazilian patients

BACKGROUND

Fc gamma RIIa is a low affinity receptor that has two co-dominantly expressed alleles, R131 and H131, which differ in their ability to bind immunoglobulin G (IgG) subclasses. Cells expressing H131 bind more efficiently complexed IgG2 and IgG3 than those expressing the R131 variant. The Fc gamma RIIa polymorphism has been shown to be associated with lupus nephritis. Here we evaluated the relevance of Fc gamma RIIa gene polymorphism in the development of lupus immune complex (IC)-mediated nephritis by comparing the genotype and allelic distribution of this receptor in lupus nephritis to ethnically matched healthy controls in Brazilians.

METHODS

119 systemic lupus erythematosus (SLE) patients and 48 healthy volunteers were recruited. Fc gamma RIIa genotyping was performed by PCR with allele-specific primers to distinguish between the two allelic forms (H131 and R131).

RESULTS

Comparison of Fc gamma RIIa genotypes distribution in SLE patients with nephritis and in controls showed a significant increase in Fc gamma RIIa-R131 homozygosity (P < or = 0.02). The genotype distribution in lupus nephritis (45% with Fc gamma RIIa-R/R131, 30% with H/R131 and 25% with H/H131) was distinct from that observed in controls (21% with Fc gamma RIIa-R/R131, 52% with H/R131 and 27% with H/H131). In contrast, there was no difference in the distribution of Fc gamma RIIa genotypes in lupus without nephritis and controls (P = 0.3). Reinforcing the relevance of Fc gamma RIIa polymorphism in IC-mediated nephritis, patients with renal failure had an over-representation of the R131 allele (70%) when compared with normal controls (47%) (P = 0.06).

CONCLUSIONS

The skewed distribution of Fc gamma RIIa genotypes with the predominance of homozygous R/R131 genotype observed in lupus nephritis emphasizes its importance as a heritable risk factor for IC-mediated renal injury in Brazilian lupus patients.

Analysis of Fc gamma receptor II (CD32) polymorphism in populations of African and South Asian ancestry reveals east-west geographic gradients of allele frequencies

Analysis of FcgammaRIIA alleles in Pakistanis and in Trinidadians of South Asian, African and mixed ancestry revealed no significant differences between Trinidadian South Asians and Pakistanis. H131 homozygotes were more common among Trinidadian South Asians than among Africans and those of mixed ancestry. Comparison with other populations revealed east-west geographic gradients of allele frequencies.

Molecular nature of antigens implicated in immune neutropenias

Granulocyte (neutrophil) antibodies can cause autoimmune neutropenia, drug-induced neutropenia, immune neutropenia after bone marrow transplantation, neonatal immune neutropenia, refractoriness to granulocyte transfusions as well as febrile and pulmonary transfusion reactions. In the last decade, considerable progress has been made in the characterization of the implicated antigens. In 1998, the Granulocyte Antigen Working Party of the ISBT introduced a new nomenclature for human neutrophil alloantigens (HNA), which is based on the antigens' glycoprotein location. In the HNA nomenclature the immunogenic (glyco-) proteins are indicated by arabic numbers followed by a letter of the alphabet which identify the (glyco-) proteins' polymorphisms, i.e. the specific antigens. Currently, seven HNA antigens are assigned to five systems. The HNA-1a, HNA-lb and HNA-1c antigens, the former NA1, NA2, and SH antigens, have been identified as polymorphic forms of the neutrophil Fc gamma receptor IIIb (CD16b) encoded by three alleles. Recently, we could elucidate the primary structure of the HNA-2a antigen, the former NB1. We could identify the HNA-2a-bearing glycoprotein as a novel member of the Ly-6/uPAR superfamily which has been clustered meanwhile as CD177. The HNA-3a antigen, the former 5b, is located on a 70-95 kDa glycoprotein. However, its molecular basis is still unknown. Finally, the HNA-4a and HNA-5a antigens, the former MART and OND, were found to be caused by single nucleotide mutations in the alphaM (CD11b) and alphaL (CD11a) subunits of the leucocyte adhesion molecules (beta2 integrins). The glycoproteins CD11b, CD16b, and CD177 have been found to be also frequent targets of autoantibodies - approximately 30% of neutrophil autoantibodies are directed against CD16b. Characterization of granulocyte antigens have expanded our diagnostic tools by the introduction of genotyping techniques and immunoassays for antibody identification. In addition, it allowed new insights in the pathophysiology of immune neutropenias and transfusion reactions. Ongoing studies will further improve the prevention and management of granulocyte antibody-mediated diseases.

Molecular variability in Amerindians: widespread but uneven information

A review was made in relation to the molecular variability present in North, Central, and South American Indian populations. It involved results from ancient DNA, mitochondrial DNA in extant populations, HLA and other autosomal markers, X and Y chromosome variation, as well as data from parasitic viruses which could show coevolutionary changes. The questions considered were their origin, ways in which the early colonization of the continent took place, types and levels of the variability which developed, peculiarities of the Amerindian evolutionary processes, and eventual genetic heterogeneity which evolved in different geographical areas. Although much information is already available, it is highly heterogeneous in relation to populations and types of genetic systems investigated. Unfortunately, the present trend of favoring essentially applied research suggest that the situation will not basically improve in the future.

Molecular nature of granulocyte antigens

Granulocyte (neutrophil) antibodies can cause febrile and pulmonary (TRALI) transfusion reactions as well as immune neutropenias. In the last decade enormous efforts have been made to characterize the implicated alloantigens. The NA1, NA2, and SH antigens could be identified as polymorphic forms of the neutrophil Fc gammaReceptor IIIb encoded by three alleles. The antigens MART and OND have been located on the leucocyte adhesion molecules (beta2 integrins) and found to be caused by single nucleotide mutations in the alphaM (CD11b) and alphaL (CD11a) subunits. We have succeeded in throwing light on the primary structure of the NB1 antigen, which has recently been clustered as CD177. Based on these findings, the Granulocyte Antigen Working Party of the ISBT introduced in 1998 a new nomenclature for human neutrophil alloantigens (HNA nomenclature) based on the antigen's glycoprotein location. Elucidation of the molecular nature of granulocyte antigens now allows antigen identification by glycoprotein-specific immunoassays and genotyping by DNA techniques. Thus, considerable progress has been made in the characterization of granulocyte antigens. Further studies will improve our diagnostic tools and facilitate the prevention and management of transfusion reactions and immune neutropenias.