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Dirk Roos

Publications and source records attributed to Dirk Roos.

At least 19 recordsLinked to original sources
PubMed2006

Natural history and early diagnosis of LAD-1/variant syndrome.

The syndrome of leukocyte adhesion deficiency (LAD) combined with a severe Glanzmann-type bleeding disorder has been recognized as a separate disease entity. The variability in clinical and cell biological terms has remained largely unclear. We present data on 9 cases from 7 unrelated families, with 3 patients being actively followed for more than 12 years. The disease entity, designated LAD-1/variant syndrome, presents early in life and consists of nonpussing infections from bacterial and fungal origin, as well as a severe bleeding tendency. This is compatible with 2 major blood cell types contributing to the clinical symptoms (ie, granulocytes and platelets). In granulocytes of the patients, we found adhesion and chemotaxis defects, as well as a defect in NADPH oxidase activity triggered by unopsonized zymosan. This last test can be used as a screening test for the syndrome. Many proteins and genes involved in adhesion and signaling, including small GTPases such as Rap1 and Rap2 as well as the major Rap activity-regulating molecules, were normally present. Moreover, Rap1 activation was intact in patients' blood cells. Defining the primary defect awaits genetic linkage analysis, which may be greatly helped by a more precise understanding and awareness of the disease combined with the early identification of affected patients.

Autoantigens↗
PubMed2006

Molecular basis of glutathione reductase deficiency in human blood cells.

Hereditary glutathione reductase (GR) deficiency was found in only 2 cases when testing more than 15 000 blood samples. We have investigated the blood cells of 2 patients (1a and 1b) in a previously described family suffering from favism and cataract and of a novel patient (2) presenting with severe neonatal jaundice. Red blood cells and leukocytes of the patients in family 1 did not contain any GR activity, and the GR protein was undetectable by Western blotting. Owing to a 2246-bp deletion in the patients' DNA, translated GR is expected to lack almost the complete dimerization domain, which results in unstable and inactive enzyme. The red blood cells from patient 2 did not exhibit GR activity either, but the patient's leukocytes contained some residual activity that correlated with a weak protein expression. Patient 2 was found to be a compound heterozygote, with a premature stop codon on one allele and a substitution of glycine 330, a highly conserved residue in the superfamily of NAD(P)H-dependent disulfide reductases, into alanine on the other allele. Studies on recombinant GR G330A revealed a drastically impaired thermostability of the protein. This is the first identification of mutations in the GR gene causing clinical GR deficiency.

Alleles↗
PubMed2006

Priming by tumor necrosis factor-alpha of human neutrophil NADPH-oxidase activity induced by anti-proteinase-3 or anti-myeloperoxidase antibodies.

Anti-proteinase-3 (anti-PR3) or anti-myeloperoxidase (anti-MPO) antibodies are capable of activating human neutrophils primed by TNF-alpha in vitro. We described previously the involvement of FcgammaRIIa and beta(2) integrins in this neutrophil activation. In the literature, the requirement of TNF priming has been attributed to an effect of TNF-alpha on the expression of PR3 or MPO on the cell surface. Under our experimental conditions, TNF-alpha (2 ng/ml) increased the binding of the antibody against PR3, whereas binding of the antibody against MPO could hardly be detected, not even after TNF-alpha treatment. The aim of this study was to consider (an)other(s) role(s) for TNF-alpha in facilitating the NADPH-oxidase activation by these antibodies. We demonstrate the early mobilization of the secretory vesicles as a result of TNF-induced increase in intracellular-free calcium ions, the parallel colocalization of gp91(phox), the main component of the NADPH oxidase with beta(2) integrins and FcgammaRIIa on the neutrophil surface, and the FcgammaRIIa clustering upon TNF priming. TNF-alpha also induced redistribution of FcgammaRIIa to the cytoskeleton in a dose- and time-dependent manner. Moreover, blocking CD18 MHM23 antibody, cytochalasin B, and D609 (an inhibitor of phosphatidylcholine phospholipase C) inhibited this redistribution and the respiratory burst in TNF-treated neutrophils exposed to anti-PR3 or anti-MPO antibodies. Our results indicate direct effects of TNF-alpha in facilitating neutrophil activation by these antibodies and further support the importance of cytoskeletal rearrangements in this priming process.

Antibodies↗
PubMed2006

Neutrophil responsiveness to IgG, as determined by fixed ratios of mRNA levels for activating and inhibitory FcgammaRII (CD32), is stable over time and unaffected by cytokines.

We tested the hypothesis that the ratio between the activating and inhibitory Fcgamma receptor type II (FcgammaRII) in neutrophils determines their responsiveness to immune complexes. We measured mRNA levels of FcgammaRII isoforms and observed differences in the ratio of FcgammaRIIa to FcgammaRIIb2 mRNA in granulocytes of 50 white and 10 black healthy volunteers, and found 4 discrete groups of ratios (ie, 4:1; 3:1, 2:1, or 1:1). The response to either dimeric IgG or aggregated IgG (aIgG) was assessed. Up-regulation of CD11b on the surface as well as the elastase release was significantly more pronounced in neutrophils with a high FcgammaRIIa/FcgammaRIIb2 mRNA ratio of 4:1 compared with a 2:1 or 1:1 ratio. Individual ratios as well as the functional responsiveness of neutrophils were constant over time, as was tested over 12 months. Neutrophil stimulation with various agents in vitro did not alter the FcgammaRIIa/FcgammaRIIb2 mRNA ratio in the neutrophils of these donors, in clear contrast to the findings in their mononuclear cells. We found a strong association between the 2B.4 haplotype of the FCGR2B promoter with increased transcriptional activity in individuals with 1:1 ratios and the more common low-expression 2B.1 haplotype in individuals with FcgammaRIIa/FcgammaRIIb2 mRNA ratios of 2:1, 3:1, or 4:1.

Adolescent↗
PubMed2006

Deficient alternative complement pathway activation due to factor D deficiency by 2 novel mutations in the complement factor D gene in a family with meningococcal infections.

The complement system is an essential element in our innate defense against infections with Neisseria meningitidis. We describe 2 cases of meningococcal septic shock, 1 of them fatal, in 2 children of a Turkish family. In the surviving patient, alternative pathway activation was absent and factor D plasma concentrations were undetectable. Concentrations of mannose-binding lectin (MBL), C1q, C4 and C3, factor B, properdin, factor H, and factor I were normal. Mutation analysis of the factor D gene revealed a T638 > G (Val213 > Gly) and a T640 > C (Cys214 > Arg) mutation in the genomic DNA from the patient, both in homozygous form. The consanguineous parents and an unaffected sister had these mutations in heterozygous form. In vitro incubation of factor-D-deficient plasma of the boy with serogroup B N meningitidis showed normal MBL-mediated complement activation but no formation of the alternative pathway C3-convertase C3bBbP, and severely decreased C3bc formation and terminal complement activation. The defect was restored after supplementation with factor D. In conclusion, this is the second report of a factor D gene mutation leading to factor D deficiency in a family with meningococcal disease. This deficiency abolishes alternative-pathway dependent complement activation by N meningitidis, and leads to an increased susceptibility to invasive meningococcal disease.

Amino Acid Substitution↗
PubMed2006

Mannan-binding lectin (MBL)-mediated opsonization is enhanced by the alternative pathway amplification loop.

The complement system is a humoral effector in the innate immune system. Three activation pathways exist in the complement system, known as the classical pathway, the lectin pathway and the alternative pathway. Dysfunction of lectin pathway activation is caused by MBL deficiency. MBL deficiency in a cohort of healthy Caucasian blood bank donors was investigated with MBL genotyping and MBL plasma concentration. Recognition of the yeast-derived zymosan by MBL was investigated with Western blot. The involvement of the alternative pathway amplification loop in enhancing MBL-mediated opsonization of zymosan was investigated in a novel opsonophagocytosis assay for flow cytometry. Sera deficient for MBL, factor D or properdin were tested, and purified MBL, factor D or properdin were used to recover opsonization. The optimal receiver-operator characteristic (ROC) cut-off value for dividing the Caucasian cohort in MBL-sufficient and MBL-deficient was calculated at 0.7 microg/ml. Thirty-eight percent of the group had concentrations below 0.7 microg/ml. Zymosan eluates opsonized with MBL-sufficient sera contain high oligomers of MBL, while eluates from MBL-deficient donors contained hardly any MBL. The MBL-, factor D- and properdin-deficient sera showed reduced opsonophagocytosis by human control neutrophils, as compared to normal MBL-sufficient sera. This reduction in opsonization was restored to normal levels by addition of purified MBL, factor D and properdin. The absence of opsonization in the factor D- and properdin-deficient sera, but presence in normal serum after blocking with anti-C1q-F(ab)2 and anti-MBL-F(ab)2, demonstrates the involvement of the amplification loop in MBL-initiated zymosan opsonization, even at very low serum concentrations (up to 3%, v/v). In conclusion, our data demonstrate that the MBL-mediated route of complement activation depends on the alternative pathway amplification loop for optimal opsonization of zymosan.

Cohort Studies↗
PubMed2006

Chronic granulomatous disease caused by mutations other than the common GT deletion in NCF1, the gene encoding the p47phox component of the phagocyte NADPH oxidase.

Chronic granulomatous disease (CGD) is an inherited immunodeficiency caused by defects in any of four genes encoding components of the leukocyte nicotinamide dinucleotide phosphate, reduced (NADPH) oxidase. One of these is the autosomal neutrophil cytosolic factor 1 (NCF1) gene encoding the p47phox protein. Most (>97%) CGD patients without p47phox (A47 degrees CGD) are homozygotes for one particular mutation in NCF1, a GT deletion in exon 2. This is due to recombination events between NCF1 and its two pseudogenes (psiNCF1) that contain this GT deletion. We have previously set up a gene-scan method to establish the ratio of NCF1 genes and pseudogenes. With this method we now found, in three CGD families patients with the normal number of two intact NCF1 genes (and four psiNCF1 genes) and in six CGD families, patients with one intact NCF1 gene (and five psiNCF1 genes). All patients lacked p47phox protein expression. These results indicate that other mutations were present in their NCF1 gene than the GT deletion. To identify these mutations, we designed PCR primers to specifically amplify the cDNA or parts of the genomic DNA from NCF1 but not from the psiNCF1 genes. We found point mutations in NCF1 in eight families. In another family, we found a 2,860-bp deletion starting in intron 2 and ending in intron 5. In six families the patients were compound heterozygotes for the GT deletion and one of these other mutations; in two families the patients had a homozygous missense mutation; and in one family the patient was a compound heterozygote for a splice defect and a nonsense mutation. Family members with either the GT deletion or one of these other mutations were identified as carriers. This knowledge was used in one of the families for prenatal diagnosis.

Adolescent↗
PubMed2005

An analysis of genetic variation across the MBL2 locus in Dutch Caucasians indicates that 3' haplotypes could modify circulating levels of mannose-binding lectin.

Mannose-binding protein (MBL) is a critical component of innate immunity and provides first-line protection against pathogens. Both circulating MBL serum levels and functional activity have been correlated with common genetic variants in the MBL2 gene. Associations between MBL deficiency and severe infections have been reported in immuno-incompetent patients and for autoimmune disorders; however, measured MBL serum levels do not fully correlate with the 'secretor haplotypes'. Previously, the MBL2 locus was resequenced and determined that a recombination hotspot divides MBL2 into two haplotype blocks. It was sought to investigate whether additional variants, in either block structure could associate with MBL serum levels. Therefore, 31 common variants were analysed across the locus in 212 DNA samples of healthy Caucasian individuals with known MBL serum concentrations. The additional 5' variants were in strong linkage to the elements of the 'secretor haplotypes'; functional alleles B, C and D also lie on restricted haplotypes. Four variants in the 3' block (Ex4-1483T>C, Ex4-1067G>A, Ex4-901G>A and Ex4-710G>A) are components of a distinct haplotype block. The results of this study suggest that additional 5' variants as well as markers of distinct 3' haplotype blocks in MBL2 may contribute to circulating protein levels, but further studies are required to confirm these observations. Last, there could be a selective advantage for diversification of the 3' region of the gene.

Adolescent↗
PubMed2005

A donor splice site mutation in intron 1 of CYBA, leading to chronic granulomatous disease.

Chronic granulomatous disease (CGD) is a rare congenital disorder in which the patients' phagocytes fail to kill ingested microbes due to an inability to generate superoxide and other microbicidal oxygen derivatives. This inability is caused by mutations in one of the four components of the phagocyte-specific NADPH oxidase. A small subgroup of CGD patients has mutations in the CYBA gene that encodes the p22-phox subunit of the NADPH oxidase. This subunit forms, together with gp91-phox, a flavocytochrome b(558) heterodimer in the phagocyte plasma membrane. Expression of both subunits is required for normal expression of this heterodimer. Here, we report an autosomal recessive CGD patient with neutrophils that did not express flavocytochrome b(558) and did not generate superoxide upon activation. Analysis of genomic DNA revealed a 4-bp deletion at the exon-1/intron-1 boundary in CYBA (IVS1+4_7delAGTG). In the patient's cDNA, we found a low expression of an abnormal product, containing exon 1 extended by 79 nucleotides from intron 1, joined to exon 2. This extension is apparently caused by the activation of a cryptic donor splice site with a GT sequence at position 84-85 in intron 1. Both parents of the patient had the same mutation in their genomic DNA, in heterozygous form, but their cDNA contained exclusively the wild-type p22-phox cDNA sequence, indicating that the mutant mRNA was labile. This is, as far as we know, the first description of the molecular and clinical consequences of a donor splice site mutation in intron 1 of any gene reported so far.

Base Sequence↗
PubMed2005

Activation of AP-1 through reactive oxygen species by angiotensin II in rat cardiomyocytes.

Cardiovascular pathogenesis induced by angiotensin II (Ang-II) is a complex process often connected to oxidative stress. In the present study we show that, 4 h after addition, Ang-II induces a four- to fivefold increase in AP-1 activity in cultured neonatal rat cardiomyocytes and that the intracellular level of reactive oxygen species (ROS) correlates with the extent of AP-1 binding activity. Ang-II stimulated ROS generation in rat cardiomyocytes in a dose- and time-dependent manner. These effects of Ang-II were suppressed by the Ang-II receptor type I (AT1) inhibitor CV-11974 as well as by the antioxidants diphenylene iodonium (DPI) and N-acetyl-L-cysteine (NAC), but not by AT2 antagonist PD 122319. Furthermore, Ang-II induced a two- to threefold increase in protein synthesis and cell size during 12-24 h, which could be inhibited by CV-11974 as well as by DPI and NAC. Because the rat cardiomyocytes strongly expressed gp91(phox), this suggests that ROS generated in a gp91-containing NADPH oxidase are involved in signal transduction leading to AP-1 activation. Together, these findings indicate that Ang-II elicits the activation of the redox-sensitive AP-1 via ROS through AT1, resulting in effects on cardiomyocyte function such as hypertrophy.

Acetylcysteine↗
PubMed2005

Single-cell Raman and fluorescence microscopy reveal the association of lipid bodies with phagosomes in leukocytes.

Cellular imaging techniques based on vibrational spectroscopy have become powerful tools in cell biology because the molecular composition of subcellular compartments can be visualized without the need for labeling. Using high-resolution, nonresonant confocal Raman microscopy on individual cells, we demonstrate here that lipid bodies (LBs) rich in arachidonate as revealed by their Raman spectra associate with latex bead-containing phagosomes in neutrophilic granulocytes. This finding was corroborated in macrophages and in PLB-985 cells, which can be induced to differentiate into neutrophil-like cells, by selective staining of LBs and visualization by confocal fluorescence microscopy. We further show that the accumulation of LBs near phagosomes is mediated at least in part by the flavohemoprotein gp91phox (in which "phox" is phagocyte oxidase), because different LB distributions around phagocytosed latex beads were observed in WT and gp91phox-deficient PLB-985 cells. gp91phox, which accumulates in the phagosomal membrane, is the catalytic subunit of the leukocyte NADPH oxidase, a critical enzyme in the innate immune response. Finally, time-lapse fluorescence microscopy experiments on neutrophils revealed that the LB-phagosome association is transient, similar to the "kiss-and-run" behavior displayed by endosomes involved in phagosome maturation. Because arachidonic acid (AA) has been shown to be involved in NADPH oxidase activation and phagosome maturation in neutrophils and macrophages, respectively, the findings reported here suggest that LBs may provide a reservoir of AA for local activation of these essential leukocyte functions.

Biophysics↗
PubMed2005

Hematologic abnormalities in Shwachman Diamond syndrome: lack of genotype-phenotype relationship.

Shwachman-Diamond syndrome (SDS) is an autosomal-recessive disorder characterized by short stature, exocrine pancreatic insufficiency, and hematologic defects. The causative SBDS gene was sequenced in 20 of 23 unrelated patients with clinical SDS. Mutations in the SBDS gene were found in 75%, being identical in 11 patients. Hematologic parameters for all 3 lineages were determined over time such as absolute neutrophil counts (ANCs), granulocyte functions, and erythroid and myeloid colony formation (erythroid burst-forming unit [BFU-E] and granulocyte-monocyte colony-forming unit [CFU-GM]) from hematopoietic progenitor cells, percentage of fetal hemoglobin (HbF), and platelet counts. Persistent neutropenia was present in 43% in the absence of apoptosis and unrelated to chemotaxis defects (in 65%) or infection rate. Irrespective of the ANC in vivo, abnormal CFU-GM was observed in all patients with SDS tested (14 of 14), whereas BFU-E was less often affected (9 of 14). Cytogenetic aberrations occurred in 5 of 19 patients in the absence of myelodysplasia. One child died during allogeneic bone marrow transplantation. In conclusion, neutropenia and defective chemotaxis did not result in severe clinical infection in SDS. CFU-GMs were impaired in all patients tested. From the SBDS sequence data, we conclude that in patients with genetically proven SDS a genotype-phenotype relationship in SDS does not exist in clinical and hematologic terms.

Abnormalities, Multiple↗
PubMed2005

Acute lymphoblastic leukemia in a patient with chronic granulomatous disease and a novel mutation in CYBB: first report.

We report for the first time a child with chronic granulomatous disease (CGD) who developed acute lymphoblastic leukemia (ALL). The diagnosis of CGD was made at the age of 4 months, by studies of his neutrophil functions. The superoxide production of the cells was negligible, as was the bactericidal activity. He was found to have a deficiency of the gp91(phox) subunit of the leukocyte NADPH oxidase, with the X-linked inheritance of the disease. DNA analysis revealed a C nucleotide insertion between C1028 and T1029. This insertion has not been described before and causes a frameshift and a premature stop codon at amino-acid position 347. The mother was found to be a carrier of this mutation. At the age of 16 months, the patient developed T-cell ALL. He was treated for 2 years, and today, 10 years since the diagnosis, he is disease-free. During the course of ALL and later, he suffered from recurrent severe pyogenic infections, but careful detection of the etiological agent and promptly instituted specific treatment resulted in his complete recovery. Although primary immune deficiencies have been reported to have an increased tendency to develop malignancies, until now there have been no reports of CGD patients with ALL.

Antineoplastic Agents↗
PubMed2005

Parenteral lipids modulate leukocyte phenotypes in whole blood, depending on their fatty acid composition.

To characterize the immunological effects of various lipids that are applied as part of total parenteral nutrition (TPN) formulations, we analyzed phenotypical changes in leukocytes following lipid exposure. Importantly, the study was performed with whole blood in order to prevent the functional changes that are induced by isolation procedures. Briefly, blood samples from 10 healthy volunteers were incubated with lipids containing pure long-chain triglycerides (L), mixed long- and medium-chain triglycerides (LM), synthetic structured lipids (SL), or emulsions based on olive oil (OO), or fish oil (FO). After immune fluorescent staining, leukocyte phenotype characteristics were analyzed by flowcytometry. Exposure to LM increased in a dose-dependent manner the expression of membrane surface markers for adhesion (CD11b) and degranulation (CD66b), while decreasing CD62L, on neutrophils and monocytes. These findings demonstrate that LM activates leukocytes in peripheral whole blood. On the other hand, decreased expression of activation markers was observed with L and FO. Lipids effects on the phenotype of T lymphocytes and Natural Killer cells were not seen during incubation for up to 4 h. These results indicate that (i) the composition of TPN formulations with regard to lipid structure has implications for the function of exposed immune competent cells and (ii) medium-chain triglycerides, which have been regarded as functionally inert deliverers of fuel calories, have distinct biological effects.

Adult↗
PubMed2005

Rapid genotyping of blood group antigens by multiplex polymerase chain reaction and DNA microarray hybridization.

BACKGROUND: In the Netherlands, 500,000 blood donors are active. Blood of all donors is currently typed serologically for ABO, the Rh phenotype, and K. Only a subset of donors is typed twice for a larger set of red cell (RBC) and/or platelet (PLT) antigens. To increase the direct availability of typed RBCs and PLTs, a high-throughput technique is being developed to genotype the whole donor cohort for all clinically relevant RBC and PLT antigens. STUDY DESIGN AND METHODS: A multiplex polymerase chain reaction was developed to both amplify and fluorescently label 19 gene fragments of RBC and PLT antigens in one reaction. To test the setup of the genotyping method by microarray, a pilot study with human PLT antigen (HPA)-typed donor samples was performed. On each slide, 12 arrays are present containing 20 probes per PLT antigen system (28 for HPA-3). The allele-specific oligohybridization method was used to discriminate between two different alleles. RESULTS: Two blinded panels encompassing 94 donors were genotyped for HPA-1 through -5 and -15; no discrepancies were found compared to their serologic typing (HPA-1, -2, -3, -4, and -5) and genotyping (HPA-15; TaqMan, Applied Biosystems). CONCLUSION: This study shows that the HPA microarray provides a reliable and fast genotyping procedure. With further development an automated throughput for complete typing of large donor cohorts can be obtained.

Antigens, Human Platelet↗
PubMed2005

Plasma levels of mannan-binding lectin in relation to periodontitis and smoking.

BACKGROUND: Mannan-binding lectin (MBL) is an important molecule of innate immunity; it acts as an opsonin and stimulates the classical complement pathway. Moreover, it has been suggested that MBL acts as a weak acute phase protein. We investigated whether MBL levels are increased in periodontitis, and we tested whether individuals deficient for MBL are more susceptible to periodontitis. METHODS: A total of 219 subjects participated in the study. Plasma samples from 115 periodontitis patients and 104 healthy controls were taken, and the MBL levels were measured by enzyme-linked immunosorbent assay (ELISA). MBL levels were analyzed in relation to periodontitis, taking into consideration age, gender, ethnic and educational background, and smoking status. In some analyses, subjects with MBL plasma levels <0.8 microg/ml were considered MBL deficient. RESULTS: MBL plasma concentrations were not significantly different in moderate and severe periodontitis compared to controls (1.6, 1.4, and 1.6 microg/ml, respectively). Also, the prevalence of MBL deficiency was not found to be different between controls and moderate and severe periodontitis (45%, 37%, and 36%). However, among all subjects and among the non-deficient subjects, MBL levels were markedly increased in heavy smokers (>10 cigarettes per day), irrespective of periodontal disease status, in comparison to non-smokers and light smokers. MBL plasma levels did not show a correlation with plasma C-reactive protein (CRP) and were also not related to the prevalence of specific periodontal pathogens. CONCLUSIONS: MBL levels were not elevated in periodontitis, and MBL deficiency was not related to susceptibility for periodontitis. The fact that MBL levels were higher among heavy smokers is the subject of further investigation.

Adult↗
PubMed2004

Functional analysis of two-amino acid substitutions in gp91 phox in a patient with X-linked flavocytochrome b558-positive chronic granulomatous disease by means of transgenic PLB-985 cells.

Chronic granulomatous disease (CGD) is a rare inherited disorder in which phagocytes lack NADPH oxidase activity. The most common form is caused by mutations in the CYBB gene encoding gp91 phox protein, the heavy chain of cytochrome b(558), which is the redox element of NADPH oxidase. In some rare cases, the mutated gp91 phox is normally expressed but no NADPH oxidase can be detected. This type of CGD is called X91(+) CGD. We have previously reported an X(+) CGD case with a double-missense mutation in gp91 phox. Transgenic PLB-985 cells have now been made to study the impact of each single mutation on oxidase activity and assembly to rule out a possible new polymorphism in the CYBB gene. The His303Asn/Pro304Arg gp91 phox transgenic PLB-985 cells exactly mimic the phenotype of the neutrophils of the X(+) CGD patient. The His303Asn mutation is sufficient to inhibit oxidase activity in intact cells and in a broken cell system, whereas in the Pro304Arg mutant, residual activity suggests that the Pro304Arg substitution is less devastating to oxidase activity than the His303Asn mutation. The study of NADPH oxidase assembly following the in vitro and in vivo translocation of cytosolic factors p47 phox and p67 phox has demonstrated that, in the double mutant and in the His303Asn mutant, NADPH oxidase assembly is abolished, although the translocation is only attenuated in Pro304Arg mutant cells. Thus, even though the His303Asn mutation has a more severe inhibitory effect on NADPH oxidase activity and assembly than the Pro304Arg mutation, neither mutation can be considered as a polymorphism.

Amino Acid Substitution↗