Mannose-binding lectin (MBL) as prognostic factor in paediatric oncology patients.

Deficiency of mannose-binding lectin (MBL) has been suggested to influence duration of febrile neutropenia and prognosis in paediatric oncology patients. However, there is no consensus on the definition of MBL deficiency. In a cohort of children with cancer, we investigated (i) how to determine MBL deficiency and (ii) whether MBL is a prognostic factor for disease severity. In 222 paediatric oncology patients, 92 healthy children and 194 healthy adults, MBL plasma levels and MBL2 genotype (wild-type: A, variant: O) were determined. Event-free survival (EFS), overall survival (OS) and paediatric intensive care unit (PICU) admissions were recorded prospectively. In febrile neutropenic patients admitted to the PICU, disease severity was assessed by clinical, microbiological and laboratory parameters. An optimal cut-off value for MBL deficiency was determined to be < 0·20 µg/ml. Wild-type MBL2 genotype patients, including the XA/XA haplotype, had increased MBL levels compared to healthy individuals. MBL deficiency was associated with decreased EFS (P = 0·03), but not with need for PICU admission. A trend for a twice increased frequency of septic shock (80% versus 38%, P = 0·14), multiple organ failure (40% versus 17%, P = 0·27) and death (40% versus 21%, P = 0·27) was observed in the absence of microbiological findings. MBL deficiency was associated with decreased EFS and possibly with an increased severity of disease during PICU admission after febrile neutropenia in the absence of any association with microbiological findings. These findings suggest prognosis to be worse in MBL-deficient compared to MBL-sufficient paediatric oncology patients.

Strong relationships between disease activity, foot-related impairments, activity limitations and participation restrictions in children with juvenile idiopathic arthritis.

OBJECTIVES: To assess possible relationships between disease activity, foot-related impairments, activity limitations and participation restrictions in children with juvenile idiopathic arthritis (JIA). METHODS: Thirty-four children were studied. Disease activity was assessed with the Juvenile Arthritis Disease Activity Score in 71 joints (JADAS-71). Foot-related impairments, activity limitations and participation restrictions were measured with the Juvenile Arthritis Foot Disability Index (JAFI), the Childhood Health Assessment Questionnaire (CHAQ), self-reported or parent-reported and doctor-reported VAS scales. Relationships were quantified with Spearman's correlation coefficient. RESULTS: The mean age was 12.4±3.7 years, the median disease duration 1.5 years (interquartile range (IQR) 1.0-4.0), 88% were girls, and 76% had polyarticular disease course. The median JADAS-71 score (range 0-101) was 6 (IQR 1-13). On the JAFI sub-scores (range 0-4) 88% of the children reported some foot-related impairments (median 1.1, IQR 0.4-2.0); 82% reported some foot-related activity limitations (median 0.9, IQR 0.3-2.0), and 65% reported some foot-related participation restrictions (median 0.6, IQR 0-2.1). The median CHAQ score was 0.9 (IQR 0.1-1.8). The JADAS-71 correlated with all impairment, activity limitation and participation restriction variables (r=0.48-0.81, p<0.01). Most of the impairment variables correlated with activity limitation (r=0.39, p<0.05 to r=0.92, p<0.01) and participation restriction variables (r=0.44, p<0.05 to r=0.81, p<0.01). All activity limitation variables correlated with participation restriction variables (r=0.62-0.84, p<0.01). CONCLUSIONS: We observed strong relationships between disease activity, foot-related impairments, activity limitations and participation restrictions in children with JIA, and therefore suggest that standard screening for foot problems should be included in follow-up care for JIA patients.

Low mannose-binding lectin (MBL) levels in neonates with pneumonia and sepsis.

We investigated whether deficiency of mannose-binding lectin (MBL), a component of innate immunity, is associated with neonatal pneumonia and sepsis during the first 72 h, i.e. early onset, and during the first month after birth. In 88 neonatal intensive care patients (71 premature), MBL2 genotype and MBL plasma levels at birth were determined prospectively by Taqman analysis and enzyme-linked immunosorbent assay, respectively. Thirty-five neonates (40%) had low, i.e.

The role of mannose-binding lectin (MBL) in paediatric oncology patients with febrile neutropenia.

Children with cancer often have fever during chemotherapy-induced neutropenia, but only some develop serious infectious complications. Mannose-binding lectin (MBL) deficiency might increase infection susceptibility in these children. MBL genotype and phenotype were prospectively determined in 110 paediatric oncology patients. During febrile neutropenia, MBL concentrations were measured longitudinally in time. MBL genotype and phenotype were correlated to clinical and laboratory parameters. Structural exon-1 MBL2 mutations and the LX promoter polymorphism lead to deficient MBL concentrations. The capacity to increase MBL concentrations during febrile neutropenia was associated with MBL2 genotype. Infectious parameters did not differ between MBL-deficient and MBL-sufficient neutropenic children (n = 66). In contrast, MBL-sufficient patients had a greater risk of Intensive Care admittance (Relative Risk 1.6, 95% Confidence Interval 1.3-2.0, P = 0.04). MBL-deficient neutropenic children did not have more severe infections. However, most patients (61%) were severely neutropenic (<100 cells/microL), compromising the opsonophagocytic effector function of MBL. MBL substitution might still be beneficial in patients with phagocytic activity.

Substrate and inhibitor studies on proteinase 3.

Various amino acid and peptide thioesters were tested as substrates for human proteinase 3 and the best substrate is Boc-Ala-Ala-Nva-SBzl with a kcat/Km value of 1.0 x 10(6) M-1.s-1. Boc-Ala-Ala-AA-SBzl (AA = Val, Ala, or Met) are also good substrates with kcat/Km values of (1-4) x 10(5) M-1.s-1. Substituted isocoumarins are potent inhibitors of proteinase 3 and the best inhibitors are 7-amino-4-chloro-3-(2-bromoethoxy)isocoumarin and 3,4-dichloroisocoumarin (DCI) with kobs/[I] values of 4700 and 2600 M-1.s-1, respectively. Substituted isocoumarins, peptide phosphonates and chloromethyl ketones inhibited proteinase 3 less potently than human neutrophil elastase (HNE) by 1-2 orders of magnitude.

Determination of proteinase 3-alpha 1-antitrypsin complexes in inflammatory fluids.

Physiological inhibitors were tested for their in vitro interaction with neutrophil proteinase 3 (PR3). The major plasma proteinase inhibitor of PR3 is alpha 1AT. We have developed a radioimmunoassay (RIA) for quantitative detection of PR3-alpha 1AT complexes formed in vivo in inflammatory exudates such as synovial fluid and plasma from patients with sepsis. Levels of PR3-alpha 1AT complexes correlated significantly with levels of human neutrophil elastase (HNE)-alpha 1AT complexes. Thus, in vivo alpha 1AT not only protects against excessive HNE activity, but also against excessive PR3 activity.

Neutrophil cytoplasmic antibodies (p-ANCA) in ulcerative colitis.

AIMS: To study ulcerative colitis associated neutrophil cytoplasmic antibodies (p-ANCA) in respect of class and subclass distribution, antigen specificity, and (sub)cellular localisation of the antigen(s) to which these antibodies are directed. METHODS: p-ANCA positivity was determined using the standard indirect immunofluorescence test (IIFT). The immunoglobulin (Ig) subclass distribution of p-ANCA was investigated using monoclonal antibodies directed against IgG1, IgG2, IgG3, and IgG4. Intracellular antigen localisation studies were performed on (fractionated) neutrophils using antigen-specific antibodies. RESULTS: In contrast to vasculitis associated ANCA, ulcerative colitis p-ANCA are mainly of IgG1 and IgG3 subclass and lack IgG4. Ulcerative colitis p-ANCA are myeloid specific. IIFT data indicate that the related antigen(s) seem(s) to be located not in the cytosol, but in the granules (most likely the azurophil granules) of the neutrophil. CONCLUSIONS: p-ANCA in ulcerative colitis have a different immunoglobulin subclass distribution than the ANCA of systemic necrotising vasculitis and necrotising and crescentic glomerulonephritis. This may point to differences in immune regulation between these diseases. Both cathepsin G and lactoferrin are recognised by a subpopulation of ulcerative colitis p-ANCA. In our series, eight out of 36 (22%) of ulcerative colitis associated p-ANCA react with lactoferrin and seven (19.5%) other sera with cathepsin G. None of them recognised both antigens. The main target antigen(s) of ulcerative colitis p-ANCA still remain(s) to be identified.

Proteinase 3: substrate specificity and possible pathogenetic effect of Wegener's granulomatosis autoantibodies (c-ANCA) by dysregulation of the enzyme.

Reactivity of proteinase 3 (PR3) was tested against various amino acid and thioester substrates. The best substrate is Boc-Ala-Ala-Nva-SBzl with a kcat/Km value of 1.0 x 10(6) M-1.s-1. We also studied the effect of C-ANCA on PR3 proteolytic activity towards elastin and inactivation by alpha 1-antitrypsin (alpha 1AT). C-ANCA IgG from 8 patients with active Wegener's granulomatosis were tested and found to inhibit elastin degradation by PR3 and to prevent the inactivation of PR3 by alpha 1AT.

[Tetanus in a young unvaccinated girl after a fall in the street]. / Tetanus bij een jong ongevaccineerd meisje na een val op straat.

A 4-year-old girl developed tetanus after she had fallen on the street a week before. She had never been vaccinated and despite pressure from the family practitioner, the parents refused to allow her to be given human anti-tetanus immunoglobulin as a matter of principle after the wound had been stitched. Seven days later she was admitted to hospital with trismus and risus sardonicus. Upon initial treatment with human anti-tetanus immunoglobulin and penicillin, and subsequently metronidazole, her clinical condition deteriorated with opisthotonus and life-threatening respiratory insufficiency, upon which she was moved to the intensive-care department where she was intubated and mechanically ventilated for two weeks. Finally she made a complete clinical recovery. Thanks to the extensive national vaccination program, tetanus has become a rare disease in the Netherlands. However, the very serious course and possible fatal outcome warrant a keen attitude and adequate treatment.

Predictors of health-related quality of life in children and adolescents with juvenile idiopathic arthritis: results from a Web-based survey.

OBJECTIVE: Children with juvenile idiopathic arthritis (JIA) experience functional impairment due to joint manifestations of the disease. The aim of our present study was to assess health-related quality of life (HRQOL) and its predictors in a group of children and adolescents with JIA. METHODS: The study sample includes all JIA patients (ages 6-18 years) who consulted a pediatric rheumatologist in Amsterdam, The Netherlands, between February 2009 and March 2010. HRQOL was measured using the Paediatric Quality of Life Inventory 4.0 (ages 6-18 years). Functional ability was measured using the Childhood Health Assessment Questionnaire, and medical and sociodemographic parameters were assessed. The study sample was compared to a Dutch youth norm population including children with other chronic health conditions. The proportion of children with JIA with an impaired HRQOL (<1 SD) was evaluated and multivariate regression analyses were performed to predict HRQOL outcome. RESULTS: Of the eligible patients, 64.1% (n = 152) participated. Both children (ages 6-12 years) and adolescents (ages 13-18 years) with JIA reported a significantly lower HRQOL in almost all domains compared to either healthy controls or children with other chronic health conditions. Approximately half of the children with JIA showed an impaired HRQOL. The main predictors of HRQOL were functional ability, pain, subjective burden of medication use, and school absence. CONCLUSION: The HRQOL is severely affected in children and adolescents with JIA. These findings underline the necessity to systematically monitor HRQOL in daily clinical practice.

High prevalence of mannose-binding lectin (MBL) deficiency in premature neonates.

Mannose-binding lectin (MBL) is a component of innate immunity and thus particularly important in neonates in whom adaptive immunity is not yet completely developed. Promoter polymorphisms and structural exon-1 mutations in the MBL2 gene cause reduced or deficient MBL plasma concentrations. The aim of our study was to determine the prevalence of MBL deficiency in neonates admitted to the neonatal intensive care unit (NICU). Eighty-five NICU patients (69 premature) were included in the study. We measured MBL concentrations in umbilical cord and neonatal blood within 24 h after birth by ELISA technique. MBL2 genotypes (n = 67) were determined by Taqman analysis. MBL concentrations were measured longitudinally during three weeks in 26 premature neonates. The association between pre- and intra-partum clinical data and MBL concentrations was investigated. At birth, 29 (42%) premature and six (38%) term neonates had MBL plasma concentrations < or = 0.7 microg/ml which was regarded as deficient. Twenty-one (38%) premature and four (36%) term neonates had variant MBL2 haplotypes, corresponding to exon-1 mutations and the LXPA haplotype. MBL concentrations increased over time in neonates with wild-type MBL2 haplotypes, but not in neonates with variant haplotypes. Low MBL plasma concentrations were related to lower gestational age and variant MBL2 haplotypes. Umbilical cord and neonatal MBL plasma concentrations appeared to be similar. In conclusion, almost half of our NICU patients, especially the premature ones, were MBL-deficient at birth. These infants may be at increased risk of neonatal infections. MBL concentration can reliably be measured in umbilical cord blood and it is positively correlated with gestational and postnatal age.

Proteolysis of classic anti-neutrophil cytoplasmic autoantibodies (C-ANCA) by neutrophil proteinase 3.

C-ANCA, which are directed against neutrophil proteinase 3 (PR3), are specific markers for the diagnosis of active Wegener's granulomatosis (WG). The correlation between C-ANCA titre and WG disease activity suggests that these autoantibodies are involved in the development of WG. We have previously observed that C-ANCA interfere with PR3 proteolytic activity and with complexation of PR3 with its major physiologic inhibitor alpha 1-antitrypsin (alpha 1-AT). The possible pathogenic importance of C-ANCA may be related to the stability of C-ANCA IgG-PR3 complexes. In the present study we tested proteolysis by PR3 of human IgG and proteolysis of C-ANCA IgG complexed to the enzyme. All human IgG subclass proteins were cleaved by PR3. Digestion products were compared with those obtained by human neutrophil elastase (HNE)-mediated proteolysis of human IgG subclass proteins. Although cleavage products of similar size could be identified, the proteolytic activity of both enzymes towards human IgG differed. Furthermore, inhibiting C-ANCA IgG were cleaved into small peptides when complexed to PR3. The possible pathogenic consequences of these findings will be discussed.

A novel specificity of anticytoplasmic autoantibodies directed against eosinophil peroxidase.

Vasculitis associated anticytoplasmic autoantibodies (ANCA) are directed against enzymes in the granules of both neutrophils and monocytes. These autoantibodies can be detected by indirect immunofluorescence technique (IIFT) using ethanol-fixed cytospins. We here report the identification of a novel specificity of autoantibodies, present in the sera of eight patients, that reacted only with eosinophils in the IIFT. By immunoprecipitation and ELISA experiments it was shown that the autoantibodies in these sera were directed against eosinophil peroxidase (EPO). There was no apparent influence on initial substrate conversion rate, but reduced plateau levels suggested increased inactivation of the enzyme in the course of the peroxidase reaction. Flow cytometry studies demonstrated the presence of EPO on the surface of primed eosinophils. Anti-EPO sera and purified anti-EPO immunoglobulins significantly increased the release of reactive oxygen species from primed eosinophils. The patients with anti-EPO antibodies suffered from clinically diverse disorders, with more or less generalized manifestations involving the kidneys, blood vessels, lungs and/or joints.

Molecular characteristics of anti-self antibody fragments against neutrophil cytoplasmic antigens from human V gene phage display libraries.

Recently it has been demonstrated that human antibody fragments with binding activities against self antigens can be isolated from repertoires of rearranged V genes from non-immunized humans. We have applied phage display technology to study the B cell repertoire for antibody activity against neutrophil cytoplasmic antigens. These antibodies may play an important role in Wegener's granulomatosis (WG) and related forms of vasculitides. Autoantibodies in patients with WG are directed against proteinase 3. The immunodominant antigen in other forms of vasculitis is myeloperoxidase, but the B cell response can also be directed against other neutrophil enzymes, e.g. lysozyme, human neutrophil elastase, lactoferrin and cathepsin G. We show here that anti-self reactivity against neutrophil cytoplasmic antigens can be detected in the rearranged V gene repertoire of healthy individuals and that the reactivity can be directed against structural related epitopes which are present on different neutrophil cytoplasmic antigens. The scFv with binding activities were sequenced and the V gene usage, the level of somatic mutations and the immunoserological characteristics of the antibody fragments are discussed. Further evidence is presented that antibody fragments consisting only of a heavy chain variable domain can recognize neutrophil cytoplasmic antigens in a specific manner. These single-domain antibody fragments were used in experiments designed to establish the relative role of the light chain variable domains in antigen binding.

Relevance of classic anti-neutrophil cytoplasmic autoantibody (C-ANCA)-mediated inhibition of proteinase 3-alpha 1-antitrypsin complexation to disease activity in Wegener's granulomatosis.

In the sera of patients with Wegener's granulomatosis (WG), C-ANCA can be detected that are directed against proteinase 3 (PR3). We have previously observed that C-ANCA interfere with PR3 proteolytic activity and with complexation of PR3 with its major physiologic inhibitor, alpha 1-antitrypsin (alpha 1AT). In the present study we investigated whether this inhibitory effect of C-ANCA on PR3-alpha 1AT complexation correlates with clinical activity of WG. Serial serum samples of eight consecutive patients with histologically proven relapses of WG were tested. At the moment of relapse all sera revealed inhibitory activity towards PR3-alpha 1AT complexation (median 22%, range 10-59%). Disease activity score (r = 0.87, P < 0.02) and C-reactive protein (CRP) levels (r = 0.66, P < 0.1) correlated with C-ANCA inhibition of PR3-alpha 1AT complexation, while they did not correlate with the C-ANCA titre detected by indirect immunofluorescence (IIF) nor with IgG anti-PR3 antibody level measured by ELISA. The inhibitory effect of C-ANCA on PR3-alpha 1AT complexation had risen significantly at the moment of relapse compared with values 3 months (P < 0.05) and 6 months (P < 0.01) before relapse. Eight patients with established WG and positive for C-ANCA but without clinical evidence of relapse served as controls. In this group no inhibitory effect of C-ANCA on PR3-alpha 1AT complexation was observed in 7/8 patients sera. Sera of one control patient contained moderate C-ANCA inhibitory activity towards PR3-alpha 1AT complexation, which remained at a constant level during the 6 months period of observation. Thus, disease activity in WG appears to be more closely related to C-ANCA inhibitory activity towards PR3-alpha 1AT complexation.

The 40-kDa Fc gamma receptor (FcRII) on human neutrophils is essential for the IgG-induced respiratory burst and IgG-induced phagocytosis.

Neutrophils express two types of receptor for the Fc region of IgG, FcRII and FcRIII. Per neutrophil, 10,000 to 20,000 molecules of FcRII (40 kDa) and 100,000 to 200,000 molecules of FcRIII (50 to 80 kDa) are expressed. Via these receptors, neutrophils bind IgG complexes that contain more than one IgG molecule. This binding activates functional processes, such as the respiratory burst and phagocytosis. We studied the contribution of FcRII and FcRIII in the activation of these processes, using well-defined complexes (both large and small) in combination with mAb against FcRII and FcRIII. Small (dimeric) IgG complexes appeared to bind via FcRIII. However, binding to FcRIII alone, when FcRII is blocked by an anti-FcRII mAb, did not induce a respiratory burst. Induction of the respiratory burst by a large immune complex, such as Staphylococcus aureus Wood opsonized with IgG antibodies, was mediated by binding to FcRII, because it was blocked by an anti-FcRII mAb but not by an anti-FcRIII mAb. This indicates that these IgG-opsonized bacteria can cross-link FcRII and activate the cells without the need to adhere to the FcRIII. The respiratory burst induced by IgG-latex was not inhibited by an anti-FcRII mAb, because the avidity for FcRII of IgG-latex, a particle of the same size as a Staphylococcus but with a two to three times higher IgG content, is increased by its simultaneous binding to FcRIII. This enhanced avidity results in removal of anti-FcRII mAb from the FcRII by IgG-latex. This increased avidity of large complexes for FcRII, created by concurrent binding to FcRIII, is not necessary for activation of human neutrophils, because neutrophils from patients with paroxysmal nocturnal hemoglobinuria, with about 10% of the normal FcRIII expression, showed a normal metabolic response upon addition of IgG-latex. Phagocytosis of IgG-opsonized 14C-labeled S. aureus Wood was inhibited equally well by anti-FcRII mAb and by anti-FcRII in combination with anti-FcRIII mAb. Thus, FcRII is not only essential for the IgG-induced activation of the NADPH oxidase system, but also for the IgG-induced phagocytosis.