FcgammaRIIIA Gene Research Articles

Survival dimensionality reduction (SDR): development and clinical application of an innovative approach to detect epistasis in presence of right-censored data

BackgroundEpistasis is recognized as a fundamental part of the genetic architecture of individuals. Several computational approaches have been developed to model gene-gene interactions in case-control studies, however, none of them is suitable for time-dependent analysis. Herein we introduce the Survival Dimensionality Reduction (SDR) algorithm, a non-parametric method specifically designed to detect epistasis in lifetime datasets.ResultsThe algorithm requires neither specification about the underlying survival distribution nor about the underlying interaction model and proved satisfactorily powerful to detect a set of causative genes in synthetic epistatic lifetime datasets with a limited number of samples and high degree of right-censorship (up to 70%). The SDR method was then applied to a series of 386 Dutch patients with active rheumatoid arthritis that were treated with anti-TNF biological agents. Among a set of 39 candidate genes, none of which showed a detectable marginal effect on anti-TNF responses, the SDR algorithm did find that the rs1801274 SNP in the FcγRIIa gene and the rs10954213 SNP in the IRF5 gene non-linearly interact to predict clinical remission after anti-TNF biologicals.ConclusionsSimulation studies and application in a real-world setting support the capability of the SDR algorithm to model epistatic interactions in candidate-genes studies in presence of right-censored data.Availability: http://sourceforge.net/projects/sdrproject/

The loss of the CD16 B73.1/Leu11c epitope occurring in some primary immunodeficiency diseases is not associated with the FcγRIIIa-48L/R/H polymorphism

The loss of the CD16a, Fc receptor for IgG type III, (FcgammaRIIIa) B73.1/Leu11c binding epitope, detected by the monoclonal antibody (mAb) used in routine enumeration of NK cells or monocytes, has been observed in children with recurrent viral infections. It has also been linked with the change of leucine (L) to histidine (H) or arginine (R) at amino acid position 48 (FcgammaRIIIa-48L/R/H) in the CD16a receptor. The reactivity of the anti-CD16a clone B73.1/Leu11c mAb with monocytes and NK cells was examined in patients with primary immunodeficiencies (n=167), gastrointestinal malignancies (n=91) and healthy subjects (n=88). Cells of only 12 children, 11 with diagnosed primary immunodeficiency and one with recurrent bacterial infections were not reactive with B73.1/Leu11c mAb. In contrast to previous findings, no linkage between the loss of B73.1/Leu11c binding epitope and herpes virus infections was observed. Furthermore, the sequence analysis of the FcgammaRIIIa gene performed in these 12 patients and 11 healthy subjects revealed that all of them had FcgammaRIIIa-48L/L genotype. Thus, the loss of B73.1/Leu11c binding epitope was not associated with the FcgammaRIIIa-48 polymorphism. The commonly described FcgammaRIIIa-158 polymorphism was determined to be 158V/V in 11 patients and 5 healthy subjects. Moreover, no linkage between FcgammaRIIIa-48L/L and -158F/F genotypes was observed. It is suggested that the loss of the B73.1/Leu11c binding epitope is connected with primary immunodeficiency disorders, but not associated with the FcgammaRIIIa-48 polymorphism.

Efficacy of rituximab therapy on diffuse large B-cell lymphoma with different Fcgamma RIIIA gene polymorphisms: a prospective study

To evaluate the impact of FcgammaRIIIA gene polymorphism on the response to rituximab therapy in newly diagnosed diffuse large B-cell lymphoma (DLBCL). Thirty-four patients with newly diagnosed, histologically proven CD20-positive DLBL received rituximab combined chemotherapy (CHOP regimen) for 6 - 8 courses of 21 days. Peripheral blood samples were collected from these 34 patients and 20 healthy blood donors. PCR was used to detect the FcgammaRIIIA polymorphisms. The initial efficacy was evaluated based on the criteria for non-Hodgkin lymphoma by International Working Group. The FcgammaRIIIA phenotypes of the 34 patients included VV type (n = 11), FF type (n = 5), and VF type (n = 18). After 6 courses of rituximab treatment combined with chemotherapy, the overall response rate was 79%, and the response rates were 82% and 83% in the VV type and VF type patients respectively, both significantly higher than that in the FF type patients (60%, P = 0.04). The most common FcgammaRIIIA polymorphism in DLCL is VF type, followed by VV and FF types. The patients with FcgammaRIIIA VV and VF types are more sensitive to the initial treatment of rituximab combined with chemotherapy compared to the patients with FF type.

Meta analysis on the association between FcγRIIa-R/H131 polymorphisms and systemic lupus erythematosus

In order to study the association between FcgammaRIIa gene polymorphisms and the risk of systemic lupus erythematosus (SLE) and lupus nephritis, relevant studies were identified from electronic databases. A meta-analysis of relevant studies was performed for heterogeneity test and pooled OR calculation. When all groups were pooled, a significant association of FcgammaRIIa-R131 allele and increased SLE risk was found. But this association was not observed in lupus nephritis. In the subgroup analysis, a clear effect of R allele in SLE was shown in European and Asian subgroups. Similarly, RR homozygous genotype was found to be a risk factor of SLE and lupus nephritis. The association between RR genotype and SLE was shown in European and Asian descents. However, the association between RR genotype and lupus nephritis was not found in any ethnic subgroups. Taken together, our study suggests that the FcgammaRIIa-R/H131 polymorphism might contribute to the susceptibility to SLE and lupus nephritis.

Association study of IL2/IL21 and FcgRIIa: significant association with the IL2/IL21 region in Scandinavian coeliac disease families

The first genome-wide association study performed in a UK coeliac disease (CD) case-control cohort revealed association with a linkage disequilibrium block containing the KIAA1109/Tenr/IL2/IL21 genes. Also recently, an association with a non-synonymous polymorphism in FcgammaRIIa (CD32a) was reported in CD with an unusually strong P-value. We aimed to replicate the reported associations with the single nucleotide polymorphisms rs13119723 A>G and rs6822844 G>T in the KIAA1109/Tenr/IL2/IL21 region and rs1801274 G>A in the FcgammaRIIa gene in a family sample consisting of 325 Swedish/Norwegian families using the robust transmission disequilibrium test. The family sample used in this study included 100 families with two or more children affected by CD and 225 families with one affected child. We could confirm significant association between the polymorphisms rs13119723 A>G and rs6822844 G>T located in the KIAA1109/Tenr/IL2/IL21 region and CD (P-value 0.001 and 0.002, respectively). However, we found no association with the FcgammaRIIa rs1801274 G>A polymorphism (P-value=0.3). In conclusion, our results support the KIAA1109/Tenr/IL2/IL21 region as a true CD susceptibility region.

Clinical relevance of TLR2, TLR4, CD14 and FcγRIIA gene polymorphisms in Streptococcus pneumoniae infection

Streptococcus pneumoniae is the most common cause of community-acquired pneumonia and a major cause of morbidity and mortality throughout the world. It has been a major research priority to identify gene polymorphisms responsible for/associated with susceptibility and severity of S. pneumoniae infection to gain a better understanding of host genetic variants and their influence and clinical relevance to pneumococcal infections. In the present study, polymorphisms in several candidate genes, including TLR2-Arg/Gln753, TLR4-Asp/Gly299, TLR4-Thr/Ile399, CD14-159C/T and FcgammaRIIA-R/H131, were examined in 85 children with pneumococcal sepsis as an invasive pneumococcal disease and 409 healthy blood donors as controls. The prevalence of the TLR4-299/399 polymorphisms was significantly lower in the patient population than in controls (4 vs 11%; P<0.05; odds ratio (OR) 0.3; 95% confidence interval (CI) 0.1-1), while the prevalence of the CD14-159CC and FcgammaRIIA-R/R131 genotypes was significantly higher (35 vs 25%; P<0.05; OR 1.7; 95% CI 1-2.8 and 39 vs 21%; P<0.001; OR 2.5; 95% CI 1.4-4, respectively). Further, only 35% of patients carried either low-risk genotypes or protective genotypes in contrast to 61% of controls (P<0.0001; OR 2.8; 95% CI 1.7-4.6). We conclude that genetic variability in the TLR4, CD14 and FcgammaRIIA genes is associated with an increased risk of developing invasive disease in patients who are infected with S. pneumoniae.

Pathogenesis of chronic immune thrombocytopenic purpura

This article summarizes recent insights into the pathophysiology of immune thrombocytopenic purpura, a disorder in which autoantibodies against cell-specific glycoproteins (GPIIb-IIIa, GPIb-IX and others) accelerate platelet destruction. Autoantibodies are produced by a limited number of B-cell clones. Platelet antibodies may also impair megakaryocyte development and platelet turnover, thromobopoietin levels are normal or only modestly increased and a compensatory increase in platelet production is not effective in many patients. Patients may show impaired immune regulation manifested by increased proliferation of helper T lymphocytes. Cytotoxic T lymphocytes from patients can lyse platelets in vitro. If cytotoxic T lymphocytes are also capable of perturbing megakaryocyte function, this mechanism may contribute to impaired platelet production. Polymorphisms in the Fcgamma-RIIIa gene may correlate with response to certain forms of therapy and similar genetic approaches may help to identify subsets of patients that differ in their natural history and response to various interventions. Better understanding of autoantibody development, inhibition of thrombopoiesis and Fcgamma receptor and other polymorphisms will assume increased importance in elucidating the pathogenesis and targeting treatment of chronic immune thrombocytopenic purpura.

Multiplex family–based study in systemic lupus erythematosus: association between the R620W polymorphism of PTPN22 and the FcγRIIa (CD32A) R131 allele

A functional polymorphism in PTPN22, a gene encoding a phosphatase involved in T-cell signaling, has been associated with autoimmunity. We checked for the prevalence of the PTPN22 R620W polymorphism in multiplex families affected with systemic lupus erythematosus (SLE) and other autoimmune diseases. Its association with other polymorphisms in mannose binding lectin (MBL) and FcgammaRIIa (CD32A) genes was also studied. Deoxyribonucleic acid samples were obtained from 233 Spanish individuals who belonged to 21 families in which at least two members had been diagnosed with some autoimmune disease, mainly SLE. A healthy control population was also included (n= 129). Genotyping for the R620W single-nucleotide polymorphism (SNP) was performed by restriction fragment length polymorphism analysis of polymerase chain reaction products. Allele frequency for the T allele was slightly higher in the families with autoimmune disease, especially when considering the affected individuals (0.094 vs 0.062). Actually, 18.8% affected family members vs 11.6% controls had the polymorphism (P= 0.179). Nineteen percent of affected individuals had both the PTPN22 T and the CD32A R131 alleles, whereas only 8.5% unaffected relatives had both susceptibility alleles simultaneously [P= 0.031, odds ratios 2.508 (95% confidence interval 1.066-5.896)]. The tendency toward finding the T allele more frequently in members affected with some particular autoimmune disorder suggests that this SNP may confer susceptibility to autoimmunity. The fact that more affected than unaffected relatives carried both the T and the R131 alleles simultaneously leads us to think about the existence of a combinatorial effect between genes that could help define individuals prone to autoimmune diseases.

The synergistic effect of FC gamma receptor IIa and interleukin-10 genes on the risk to develop systemic lupus erythematosus in Thai population

Several linkage analyses have consistently shown that systemic lupus erythematosus (SLE) susceptible genes are located on chromosome 1q21-44. In this study, two major candidate genes, interleukin-10 (IL-10) and Fc gamma receptor IIa (FcgammaRIIa), within these regions were investigated in Thai SLE patients. The genotyping of three single-nucleotide polymorphisms (promoter area: -1082, -819 and -592) within IL-10 gene and one polymorphism (change amino acid at position 131) within FcgammaRIIa gene was determined in 195 SLE patients and 159 ethnically matched controls. The RR/RH genotypes of FcgammaRIIa were found to be significantly increased in SLE patients compared with healthy controls [OR = 2.01, 95% confidence interval (CI) = 1.28-3.14, P= 0.001]. Interestingly, the synergistic effect between RR/RH genotypes of FcgammaRIIa and ACC/ACC haplotype of IL-10 in susceptibility to SLE was observed (OR = 7.84, 95% CI = 1.60-52.04, P= 0.002). In addition, the FcgammaRIIa, RR homozygotes was also strongly associated with anticardiolipin antibody production (OR = 6.09, 95% CI = 1.38-30.54, P= 0.006). The result demonstrated that ACC haplotype of IL-10 gene and FcgammaRIIa R131 polymorphism can be used as marker for genetic susceptibility and severity to SLE in Thai population, particularly individuals carrying both specific genotypes.

Investigation of Fcgamma RIIA and Fcgamma RIIIA Polymorphism in Multiple Sclerosis: A Case Control Study.

Multiple Sclerosis (MS), the most common demylinating disease of the CNS, is immunologically mediated in genetically susceptible individuals. Receptors for the Fc fragment of IgG (FcgammaR) might induce inflammatory responses through linking the humoral and cellular immune responses by targeting immune complexes to effector cells. Polymorphisms in some FcgammaR genes are associated with various infectious and autoimmune diseases, probably due to their effects on different binding capacities of encoded receptors for IgG containing immune complexes. To investigate the importance of FcgammaR polymorphisms in susceptibility to MS. One hundred and fifty MS patients and 136 age and sex matched controls were genotyped for FcgammaRIIA and FcgammaRIIIA gene polymorphisms using PCR-RFLP method. The allelic and genotypic frequencies of the FcgammaRIIA and FcgammaRIIIA did not differ significantly between the MS patients and controls. There was no association between allelic polymorphism of FcgammaRIIIA and severity of disease based on Expanded Disability Status Scale (EDSS) score. However, significant association between inherited FcgammaRIIA genotype and disease activity (p=0.001) or progression index was revealed (p=0.014). EDSS values showed that FcgammaRIIA (H/H) and (H/R) genotypes were associated with a lower EDSS score in relapsing-remitting MS and in the total MS population (p=0.001) but not (R/R) genotype. Considering the detrimental role of autoantibodies in the pathogenesis of MS, our results suggest that the inherited FcgammaRIIA alleles could affect the severity of MS by influencing the clearance rate of immune complexes and autoantibodies. The results of the present study add the FcgammaRIIA gene to the gene networks which determine the severity of MS in southern Iran.

Fc gamma RIIa, IIIa and IIIb polymorphisms in Turkish children susceptible to recurrent infectious diseases

The efficacy of IgG-induced Fc gamma receptor (FcgammaR) function displays interindividual heterogeneity due to genetic polymorphisms of three FcgammaR subclasses: FcgammaRIIa, FcgammaRIIIa and FcgammaRIIIb. FcgammaR polymorphisms may contribute to disease susceptibility or may alter disease course. The aim of this study is to examine FcgammaR gene polymorphisms in Turkish children with recurrent respiratory tract infections and without well known humoral immunodeficiencies. For the patients in the study group (n=52), recurrent infection was defined as the presence of at least six infection episodes a year. Seventy-one healthy children with a maximum of two infections in a year were enrolled as the control group. Subjects in both groups had no abnormalities in serum immunoglobulins, IgG subsets and specific antibody levels. For FcgammaRIIa: H131H, H131R, R131R genotypes and 131R, 131H alleles; for FcgammaRIIIa: F158F, F158V, V158V genotypes and 158F, 158V alleles; and for FcgammaRIIIb: -NA1/NA1, NA1/NA2, NA2/NA2 genotypes and NA1, NA2 alleles were determined by using amplification refractory mutation system polymerase chain reaction (ARMS-PCR). Compared with the control group, the FcgammaRIIa-R131R genotype and 131R allele were found to be significantly elevated in the study group, and FcgammaRIIa-H131H genotype and 131H allele in the study group were significantly lower than in the control group. Genotypes and alleles related with FcgammaRIIIa and FcgammaRIIIb gene polymorphisms did not show any significant difference between the study and control groups. FcgammaRIIa gene polymorphism (R131R) may increase the risk and susceptibility for recurrent infectious diseases in children.

FcγRIIa (CD32) Polymorphism and Onchocercal Skin Disease: Implications for the Development of Severe Reactive Onchodermatitis (ROD)

The pathologic manifestations of Onchocerca volvulus infection depend on the interplay between the host and the parasite. A genetic single nucleotide polymorphism in the Fc gamma RIIa gene, resulting in arginine (R) or histidine (H) at position 131, affects the binding to the different IgG subclasses and may influence the clinical variations seen in onchocerciasis. This study investigated the relationship between this polymorphism and disease outcome. Fc gamma RIIa genotyping was performed on clinically characterized onchocerciasis patients (N = 100) and healthy controls (N = 74). Fc gamma RIIa genotype R/R131 frequencies were significantly higher among patients with severe dermatopathology (P < 0.001). Increased risk of developing this form was mostly associated with one tribe (Masalit) (OR = 3.2, 95% CI 1-9.9, P = 0.042). The H131 allele was found to be significantly associated with a reduced risk of having the severe form of the disease (adjusted OR = 0.26, 95% CI = 0.13-0.46, P < 0.001). Our findings suggest that the polymorphism influences the clinical outcome of onchocerciasis.

Identification of IgG subclasses and C-reactive protein in lupus nephritis: the relationship between the composition of immune deposits and FCgamma receptor type IIA alleles.

To characterize the subclass composition of IgG deposited in lupus glomeruli, to examine its relationship to allelic polymorphisms of IgG receptors (Fcgamma receptors [FcgammaR]), and to determine whether C-reactive protein (CRP), a ligand for FcgammaRIIa, is present in these immune deposits. Renal biopsy samples from 80 patients with lupus nephritis were examined by light microscopy and indirect immunofluorescence with IgG-subclass-specific monoclonal antibodies. FcgammaRIIA genotypes were determined using allele-specific polymerase chain reaction. Immunostaining for CRP was performed on lupus and nonlupus glomerulonephritis specimens. IgG2 and IgG3 were the predominant subclasses in immune deposits in all World Health Organization classes of nephritis. The frequency of genotypes containing the low-binding IgG2 allele, FcgammaRIIa-R131, was significantly greater than expected in patients with class III or class IV nephritis and in patients with intense IgG2 deposition. CRP, a ligand with particular affinity for FcgammaRIIa-R131, was consistently present in the renal immune deposits of lupus nephritis specimens. FcgammaRIIA genes are associated with proliferative renal disease and may contribute to disease pathogenesis. FcgammaRIIa-R131, the variant with low affinity for IgG2, has high affinity for CRP. Thus, FcgammaRIIa-R131 may contribute to impaired removal of circulating immune complexes, as well as efficiently triggering phagocyte activation and the release of inflammatory mediators within glomeruli.

Estudio del polimorfismo de receptores FcgammaIIa en pacientes chilenos con lupus eritematoso sistémico

Polymorphisms of Fc receptors for IgG (Fc gamma R) have been proposed as a genetic factor that influences susceptibility for systemic lupus erythematosus (SLE). Human Fc gamma RIIa has 2 codominantly expressed alleles, H131 and R131, which differ at amino acid position 131 in the second extracellular domain (histidine or arginine respectively) and differ substantially in their ability to bind human IgG2. The H131 allele binds IgG2 efficiently, whereas R131 binds it poorly. Because IgG2 is a poor activator of the classical complement pathway, the H131 is essential for the disposal of IgG2 immune complexes. To determine the distribution of Fc gamma RIIA genes in a cohort of Chilean SLE patients, with or without a history of lupus nephritis. We studied 52 Chilean SLE patients fulfilling the 1982 American College of Rheumatology (ACR) criteria, 20 of whom had a history of nephritis, and 44 ethnically matched disease-free controls. Fc gamma RIIa allotypes were genotyped by PCR. No significant association was observed between the low affinity Fc gamma RII receptor (FcgRIIa-R131) and the presence of SLE or lupus nephritis. However, genotype frequencies in SLE patients but not in controls, departed from the proportions predicted by the Hardy-Weinberg equilibrium, suggesting this locus might be related to the disease. Our results suggest that in Chilean patients with SLE, as well as in many other populations, the R131 allotype is not a major factor predisposing to the development of SLE or lupus nephritis.

Genetic linkage and association of Fcgamma receptor IIIA (CD16A) on chromosome 1q23 with human systemic lupus erythematosus.

Although low-affinity alleles of human Fcgamma receptor types IIA and IIIA (FcgammaRIIA and FcgammaRIIIA, respectively) polymorphisms have been associated with systemic lupus erythematosus (SLE) in case-control studies, the relative contribution of these genes to SLE susceptibility has not been resolved. We analyzed the distribution of alleles of FcgammaRIIA, FcgammaRIIIA, and FcgammaRIIIB in 126 multiplex-SLE pedigrees and FcgammaRIIA and FcgammaRIIIA in a case-control replication study, using allele-specific polymerase chain reaction and direct sequencing of genomic DNA. Statistical tests of association were performed to detect evidence of linkage between the single nucleotide polymorphisms and SLE. We found evidence for linkage at both the FcgammaRIIIA (single-point nonparametric linkage [NPL] 1.8, P = 0.038; multipoint NPL 2.7, P = 0.004) and the FcgammaRIIA (single-point NPL 2.0, P = 0.021; multipoint NPL 2.6, P = 0.006) loci, but not the FcgammaRIIIB locus. Family-based tests of association demonstrated increased transmission of the low-affinity F176 allele at the FcgammaRIIIA locus (odds ratio [OR] 2.18, P = 0.0005 by transmission disequilibrium test and P = 0.002, by pedigree disequilibrium test [PDT]), but little evidence of preferential transmission of alleles at FcgammaRIIA (P = 0.089 by PDT). Stratification by ethnicity showed preferential transmission of the associated FcgammaRIIIA allele both in families of African American ancestry and in those of European American ancestry. Despite significant linkage disequilibrium between these genes, 2- and 3-locus haplotype analysis of the extended Fcgamma receptor cluster did not reveal any significant association beyond that observed with FcgammaRIIIA alone. In a large case-control replication study of 438 patients with SLE and 219 controls, FcgammaRIIIA provided the strongest evidence of an FcgammaR-SLE association (additive model: V/V 176 versus V/F 176 OR 1.51, V/V 176 versus F/F 176 OR 1.98, P = 0.007). To our knowledge, these data are the first to demonstrate linkage and both family-based and case-control-based association of FcgammaRIIIA with SLE. These data provide genetic evidence supporting a role for the physiologically relevant single nucleotide polymorphism of the FcgammaRIIIA gene in the pathophysiology of this complex genetic disease.

Susceptibility to dengue hemorrhagic fever in vietnam: evidence of an association with variation in the vitamin d receptor and Fc gamma receptor IIa genes.

Dengue is an increasingly important cause of morbidity and mortality in the tropics, with more than a billion people at risk each year. Immunologic enhancement is thought to contribute to disease pathogenesis. Only a very small proportion of infected individuals develop life-threatening dengue hemorrhagic fever (DHF). In a large case-control study with 400 DHF patients and 300 matched controls, we have assessed five polymorphic non-HLA host genetic factors that might influence susceptibility to DHF. The less frequent t allele of a variant at position 352 of the vitamin D receptor (VDR) gene was associated with resistance to severe dengue (P = 0.03). Homozygotes for the arginine variant at position 131 of the Fc gammaRIIA gene, who have less capacity to opsonize IgG2 antibodies, may also be protected from DHF (one-tailed P = 0.03). No associations were found with polymorphisms in the mannose binding lectin, interleukin-1 (IL-4), and IL-1 receptor antagonist genes. Further studies to confirm these associations are warranted.

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

The FcgammaRIIA gene is expressed in two polymorphic forms, R131 and H131, which differ by the replacement of histidine by arginine at position 131. The FCGR3B (FcgammaRIIIB) gene exists in two allelic isoforms, known as FCGR3B1 (FcgammaRIIIB-NA1) and FCGR3B2 (FcgammaRIIIB-NA2), which differ in nucleotides 141, 147, 227, 277, and 349. An additional polymorphism is the SH antigen that is associated with the FCGR3B3 (FcgammaRIIIB-SH) allele. By use of a PCR with allele-specific primers, the allelic polymorphisms of FcgammaRIIA and FcgammaRIIIB were determined among 263 unrelated Brazilian subjects, including Amazon Indians (n = 92), blood donors (n = 85), and patients with sickle cell disease (SCD) (n = 86). Amazon Indians had a significantly higher frequency of the R131 allele than did blood donors and SCD patients (0.91 vs. 0.55 vs. 0.55; p<0.001). NA1 and NA2 gene frequencies were found to be 0.67 and 0.21 for Amazon Indians, 0.58 and 0.42 for blood donors, and 0.61 and 0.39 for SCD patients, respectively. The FcgammaRIIIB-SH allele was absent from the Amazon Indians, but 9 (10.6%) blood donors and 10 (11.6%) SCD patients expressed this allele. Overall, the data indicate that the distribution of the FcgammaRIIIB alleles is significantly different in Amazon Indians from the distribution in Brazilian blood donors or African Brazilian patients with SCD, but that it is similar to the distributions reported in Asian populations. Moreover, the distribution of the FcgammaRIIA and FcgammaRIIIB alleles among Brazilian blood donors and SCD patients is comparable to the distributions reported in whites from the United States and Europe.

Augmentation of pulmonary host defense against Pseudomonas by FcgammaRIIA cDNA transfer to the respiratory epithelium.

Fcgamma receptors on the surface of phagocytic cells bind the Fc region of IgG and mediate binding, phagocytosis, and destruction of particulate antigens opsonized by the antigen-specific IgG molecule. The present study evaluates the feasibility of converting lung epithelial cells into phagocytic cells using adenovirus (Ad) vector-mediated gene transfer of FcgammaRIIA cDNA to induce expression of the human FcgammaRIIA receptor. Binding and phagocytosis of opsonized sheep red blood cells (SRBCs) by the A549 human lung epithelial cell line after Ad-mediated FcgammaRIIA gene transfer was demonstrated using light and fluorescence microscopy and phagocytic assays with (51)Cr-labeled SRBCs. When A549 cells were infected with an Ad vector expressing a FcgammaRIIA mutant in which 2 of 3 cytoplasmic tyrosines have been replaced with phenylalanine, only binding, but not phagocytosis, of opsonized SRBCs was observed. In vivo expression of FcgammaRIIA in the lung after intratracheal administration of the AdFcgammaRIIA enhanced clearance of opsonized Pseudomonas aeruginosa from the lung in normal rats and in mice deficient in Fcgamma receptor expression. Similar results were observed with a chimeric FcgammaRIIA construct containing the extracellular domain of FcgammaRIIIA. Together, these data demonstrate that Ad-mediated FcgammaRIIA receptor cDNA expression can mediate the binding and phagocytosis of opsonized particulate antigens by normally nonphagocytic cells, suggesting that gene-transfer strategies might be used to utilize nonphagocytic cells to clear bacteria or other opsonized particulate antigens from the respiratory tract.

Separate Promoters from Proximal and Medial Control Regions Contribute to the Natural Killer Cell-specific Transcription of the Human FcγRIII-A (CD16-A) Receptor Gene

The molecular events governing the differentiation pathway of natural killer (NK) cells are not well understood. The phenotype of mature NK cells is specified by the expression of the low affinity Fc receptor for IgG (human FcgammaRIII, CD16) encoded by the FcgammaRIII-A gene. Here we report that the Pprox promoter (-198/-10) of FcgammaRIII-A stimulated by its own intron enhancer (+10/+712) was only one of the cis-elements that target the expression of a reporter gene in the immature NK cell line, YT. The transcription start sites of the FcgammaRIII-A a2/3 and a5/6 splice alternatives in NK cells were mapped to the medial -1817/-850 FcgammaRIII-A control region. Two promoters, Pmed1 (-942/-850) and Pmed2 (-1376/-1123) resided in this region and controlled for the initiation of these transcript classes encoding the known FcgammaRIII-A receptor protein. Deletion mapping studies demonstrated that the 93 base pairs -942/-850 Pmed1 sequence was sufficient to confer cell type-specific expression in YT cells. The 5' end of Pmed1 (-942 to -921) was required for full promoter function indicating the presence of an important sequence motif recognized by a YT-specific factor. Our data suggest that this motif might be a useful tool for subsequent identification of putative transcription factors uniquely active in YT and NK cells.

Identification of an Unusual Fcγ Receptor IIIa (CD16) on Natural Killer Cells in a Patient With Recurrent Infections

We found an unusual fc gamma receptor IIIa (CD16) phenotype on the natural killer (NK) cells of a 3-year-old boy, who suffered from recurrent viral respiratory tract infections since birth. He also had severe clinical problems after Bacille Calmette-Geérin (BCG) vaccination and following Epstein-Barr virus and Varicella Zoster virus infections. His peripheral blood lymphocytes contained a normal percentage and absolute number of CD3-CD7+ cells, which were positively stained with the CD16 monoclonal antibodies (MoAbs) 3G8 and CLBFcRgran1, but did marginally stain with the CD16 MoAb Lau11c/B73.1. Fc gamma RillIb expression on granulocytes appeared to be normal. NK cell function, analyzed in vitro by direct cytotoxicity on K562 target cells and ADCC-activity on P815 target cells, was normal compared with an age-matched healthy control. Sequence analysis of the Fc gamma RIIIA gene, encoding CD16 on NK cells and macrophages, showed a T to A nucleotide substitution at position 230 on both alleles, predicting a leucine (L) to histidine (H) amino acid change position 48 in the first extracellular lg-like domain of Fc gamma RIIIa, which contains the Leu11c/B73.1 epitope. The combined use of CD16 and CD56 MoAbs labeled with the same fluorescent dye, as often applied in routine immunophenotyping procedures, will leave these homozygotes undiagnosed. The pattern of infections in this patient is in agreement with the postulated function of NK cells in the immunological defense against viruses and other intracellular microorganisms. Further analysis of the NK cell function in vitro and follow-up of the clinical course of Fc gamma RIIIA-48H/H homozygotes is required to ascertain whether this genotype is causally related to an NK cell immunodeficiency.