PubMed Health⌕ Search

Biomedical subjects

P C Limburg

Publications and source records attributed to P C Limburg.

At least 19 recordsLinked to original sources
PubMed2006

Quantitation of autoantibodies in systemic autoimmune diseases: clinically useful?

Serial assessment of levels of autoantibodies has been proposed as being clinically useful in certain systemic autoimmune diseases. In particular, attention has been given to anti-dsDNA antibodies in systemic lupus erythematosus (SLE) and ANCA in the ANCA-associated vasculitides (AAV). Much controversy exists, however, concerning the value of serial testing in these diseases. We here review the various tests available for quantitation of anti-dsDNA and ANCA, and their capacity to detect changes in autoantibody levels that are associated with changes in clinical disease activity of the respective diseases. It is concluded that changes in anti-dsDNA as measured by the Farr assay and changes in ANCA as assessed by ELISA have predictive value for the occurrence of disease relapses, although this relationship is far from absolute. Consequently, treatment based on changes in levels of the respective autoantibodies only seems at present not justified, in view of the toxicity of currently available immunosuppressive regimens.

Antibodies, Antineutrophil Cytoplasmic↗
PubMed2006

p38 mitogen-activated protein kinase (MAPK) in rheumatoid arthritis.

The importance of p38 MAPK inhibitors as new drug for rheumatoid arthritis is reflected by the large number of compounds that has been developed over the last years. In this review new insights such as non-stressful activation of p38 MAPK, and the role of p38 MAPK in regulation of NF-kappaB recruitment are also discussed.

Arthritis, Rheumatoid↗
PubMed2005

Skin sensitivity to UVB irradiation in systemic lupus erythematosus is not related to the level of apoptosis induction in keratinocytes.

OBJECTIVES: Accumulation of apoptotic cells has been suggested to be involved in the pathogenesis of systemic lupus erythematosus (SLE). As sunlight exposure is one of the factors that can trigger disease activity, we hypothesized that UV light may induce increased numbers of apoptotic cells in SLE. METHODS: Fourteen SLE patients and 16 controls were irradiated with UVB to determine their minimal erythemal dose (MED). Subsequently, skin was irradiated with 1 MED and 2 MED, respectively, and after 24 h skin biopsies were analysed immunohistologically for the number of apoptotic cells and presence of pyknotic nuclear debris. RESULTS: MED was significantly decreased in SLE patients and the presence of decreased MED was associated with a history of butterfly rash. Decreased MED was not related to other skin-related ACR criteria or to autoantibody specificities. No differences were detected in the numbers of apoptotic keratinocytes between patients and controls or in the amount of pyknotic nuclear debris following 1 and 2 MED irradiation, respectively. Absolute UVB doses were correlated with the number of apoptotic keratinocytes; dose-responses did not differ significantly between patients and controls. CONCLUSIONS: Increased sensitivity of SLE patients to UVB, although associated with a history of malar rash, is not related to increased induction of apoptosis or increased levels of secondary necrosis in the skin. Thus, compared with controls, UVB-induced apoptosis is not increased in SLE patients under physiological conditions.

Adult↗
PubMed2005

Differential influence of p38 mitogen activated protein kinase (MAPK) inhibition on acute phase protein synthesis in human hepatoma cell lines.

BACKGROUND: Inhibition of intracellular signal transduction is considered to be an interesting target for treatment in inflammation. p38 MAPK inhibitors, especially, have been developed and are now in phase II clinical trials for rheumatoid arthritis (RA). OBJECTIVE: To investigate the influence of p38 MAPK inhibition on acute phase protein (APP) production, which is dependent on both JAK/STAT and p38 MAPK pathways. METHODS: The effects of p38 MAPK inhibition on APP production and mRNA expression in four human hepatoma cell lines was investigated, after stimulation with interleukin (IL)6 and/or IL1beta or tumour necrosis factor alpha. RESULTS: Two out of four cell lines produced C reactive protein (CRP), especially after combined IL6 and IL1beta stimulation. CRP production was significantly inhibited by the p38 MAPK specific inhibitor RWJ 67657 at 1 micromol/l, which is pharmacologically relevant. Fibrinogen production was also inhibited at 1 micromol/l in all cell lines. Serum amyloid A (SAA) was produced in all four lines. In contrast with CRP, SAA production was not inhibited by RWJ 67657 at 1 micromol/l. CONCLUSION: Production and mRNA expression of CRP and fibrinogen, but not SAA production and mRNA expression, were significantly inhibited by p38 MAPK specific inhibitor in hepatoma cell lines. For p38 MAPK inhibitor treatment in RA SAA might be a better marker of disease activity than CRP and fibrinogen, because SAA is not directly affected by p38 MAPK inhibition.

Acute-Phase Proteins↗
PubMed2005

Reduced uptake of apoptotic cells by macrophages in systemic lupus erythematosus: correlates with decreased serum levels of complement.

BACKGROUND: Defects in phagocytosis of apoptotic cells have a role in the pathogenesis of autoimmune diseases. Decrease of phagocytosis of apoptotic cells occurs in systemic lupus erythematosus (SLE). Factors underlying this decrease are, presently, unknown. OBJECTIVE: To analyse the expression of relevant membrane receptors of monocyte derived macrophages (MDM) from patients with SLE and assess their ability to phagocytose apoptotic cells in comparison with MDM from healthy controls. Additionally, to compare phagocytosis in the presence of SLE sera with that in normal human serum (NHS). METHODS: Human peripheral blood monocytes were isolated from patients and controls, and cultured for 7 days to obtain MDM. Membrane expression of CD14, CD18, CD36, and CD51/61 was measured. MDM were incubated with apoptotic Jurkat cells in the presence of NHS or serum from patients with active or inactive disease. RESULTS: No differences in phagocytosis capacity were found between MDM from patients and controls. Membrane expression of the respective receptors was comparable in patients and controls. However, when MDM from controls were incubated with apoptotic cells in patient serum, phagocytosis was significantly decreased in comparison with incubation in NHS. This effect depended on the patients' disease activity and could be reversed by addition of NHS. Reduced uptake of apoptotic cells was associated with decreased levels of complement C1q, C4, and C3, but not with levels of complement factor B. CONCLUSIONS: Reduced uptake of apoptotic cells by MDM from patients with SLE is not an intrinsic defect but is serum dependent and associated with decreased levels of C1q, C4, and C3.

Adult↗
PubMed2005

Levels of complement in sera from inactive SLE patients, although decreased, do not influence in vitro uptake of apoptotic cells.

BACKGROUND: Accumulation of apoptotic cells is considered relevant in the pathogenesis of systemic lupus erythematosus (SLE). Complement factors facilitate the clearance of apoptotic cells and, when decreased, might result in an increased amount of apoptotic cells found in SLE patients. OBJECTIVE: To determine the influence of complement profiles from inactive SLE patients on the in vitro phagocytosis of apoptotic cells. METHODS: Consecutive SLE patients (n=98) with inactive disease (SLEDAI < or =4) and 20 healthy controls (HC) were included. Levels of CH50, C3, C4, C1q, and C1r were measured. Human peripheral blood monocytes were isolated from healthy controls and cultured for 7 days to obtain monocyte-derived macrophages (MDM). Jurkat cells were irradiated with UVB to induce apoptosis. Phagocytosis was tested by incubation of MDM with apoptotic cells in the presence of serum and quantified as phagocytosis index (number of Jurkat cells internalized by 100 macrophages). Serum from 20 patients with CH50<65%, 20 patients with CH50 > or =65%, and 20 HC were used in this assay. RESULTS: All HC and 37% of patients had normal complement levels. CH50 level was decreased in 21% of patients, C3 in 52%, C4 in 29%, C1q in 2% and C1r in 44% of patients. Between patients and HC, differences in level of CH50, C3 and C4 were statistically significant. No difference in phagocytosis index between HC and patients, irrespective of their CH50 level, was detected. No correlation was found between the respective complement levels and phagocytosis index. CONCLUSION: In most SLE patients with inactive disease, levels of one or more complement components are decreased. However, decreased levels of complement do not result in a significantly reduced in vitro uptake of apoptotic Jurkat cells by MDM.

Adult↗
PubMed2004

Neurobiology and neuroimmunology of Tourette's syndrome: an update.

Tourette's syndrome is a childhood-onset neuropsychiatric disorder characterized by the presence of both multiple motor and vocal tics. While the pathogenesis at a molecular and cellular level remains unknown, structural and functional neuroimaging studies point to the involvement of the basal ganglia and related cortico-striato-thalamo-cortical circuits as the neuroanatomical site for Tourette's syndrome. Moreover, Tourette's syndrome has a strong genetic component, and considerable progress has been made in understanding the mode of transmission and in identifying potential genomic loci. Summaries of recent findings in these areas will be reviewed, followed by a critical overview of findings both supporting and challenging the proposed autoimmune hypothesis of Tourette's syndrome. We conclude that Tourette's syndrome is a heterogeneous disorder, and that immune factors may indeed be involved in some patients.

B-Lymphocytes↗
PubMed2004

Portal and systemic serum growth factor and acute-phase response after laparotomy or partial hepatectomy in patients with colorectal liver metastases: a prognostic role for C-reactive protein and hepatocyte growth factor.

BACKGROUND: Growth factors play a role in wound healing and tumour growth. The aim of this study was to compare the effect of partial hepatectomy (PH) and laparotomy on serum levels of growth factors and acute-phase proteins in patients with colorectal liver metastases and to correlate these levels with prognosis after PH. METHODS: Epidermal growth factor (EGF), hepatocyte growth factor (HGF), insulin like growth factor-I (IGF-I), insulin, interleukin-6 (IL-6), C-reactive protein (CRP) and serum amyloid-A (SAA) were determined in portal and systemic serum in 24 PH patients and 9 laparotomy patients. RESULTS: No differences were found in the clinicopathological characteristics of PH and laparotomy patients with the exception of the number of metastases, blood loss and operation time. The response of SAA, CRP and IGF-I was lower in PH patients than in laparotomy patients (P < 0.02). PH was associated with a higher IL-6 (P = 0.02) and HGF (P = 0.055) response than laparotomy. A higher HGF and CRP response was associated with a poorer prognosis. Total IGF-I was negatively correlated with the resected liver volume (r = -0.48, P < 0.05). CONCLUSIONS: PH is associated with a lower acute-phase and total IGF-I response and a higher HGF and IL-6 response compared with laparotomy. HGF and CRP responses had an influence on the prognosis.

Acute-Phase Proteins↗
PubMed2004

Serum amyloid P component levels are not decreased in patients with systemic lupus erythematosus and do not rise during an acute phase reaction.

BACKGROUND: Serum amyloid P component (SAP) and acute phase proteins like C-reactive protein contribute to the clearance of apoptotic cells. This response is diminished in systemic lupus erythematosus (SLE). OBJECTIVES: To analyse SAP concentrations in SLE in relation to disease activity, and investigate whether SAP reacts like an acute phase protein. METHODS: SAP was measured in 40 patients with SLE during active and inactive disease and compared with healthy controls and patients with rheumatoid arthritis and Wegener's granulomatosis. Normal SAP values were determined in 120 healthy controls by ELISA. C reactive protein and serum amyloid A (SAA) were measured in all subjects and their levels related to SAP. SAP was also measured serially in 11 patients with breast cancer treated with recombinant human interleukin-6, and in 16 patients with sepsis. RESULTS: In SLE, SAP was unaltered compared with healthy controls and was not influenced by disease activity, in contrast to C reactive protein and SAA, which increased during active disease. SAP increased in Wegener's granulomatosis but not in rheumatoid arthritis. The rise in C reactive protein and SAA was most pronounced in Wegener's granulomatosis with active disease. SAP did not change significantly during an acute phase response. No correlation was found between SAP and C reactive protein or SAA, but there was a correlation between SAA and C reactive protein (r = 0.4989, p = 0.0492). CONCLUSIONS: Patients with SLE have normal circulating SAP levels. In contrast to C reactive protein or SAA, SAP does not act as an acute phase protein.

Acute Disease↗
PubMed2004

Effects of RWJ 67657, a p38 mitogen activated protein kinase (MAPK) inhibitor, on the production of inflammatory mediators by rheumatoid synovial fibroblasts.

OBJECTIVE: To investigate the effect of the p38 mitogen activated protein kinase (MAPK) inhibitor RWJ 67657 on inflammatory mediator production by rheumatoid synovial fibroblasts (RSF). METHODS: RSF were pretreated with RWJ 67657 and stimulated with TNF alpha and/or IL-1 beta. Protein levels and mRNA expression of MMP-1, MMP-3, TIMP-1, IL-6, and IL-8 were determined, as was mRNA expression of COX-2 and ADAMTS-4. RESULTS: MMP-3 production was significantly inhibited at 1 microM RWJ 67657 and MMP-1 production at 10 microM, while TIMP-1 production was not inhibited. Inhibition of IL-6 and IL-8 protein production was seen at 0.1 microM RWJ 67657. Expression profiles of mRNA were in accordance with protein production. Inhibition of COX-2 mRNA expression occurred at 0.01 microM RWJ 67657. CONCLUSIONS: RWJ 67657 inhibits major proinflammatory mediator production in stimulated RSF at pharmacologically relevant concentrations. These findings could have important relevance for the treatment of rheumatoid arthritis.

ADAM Proteins↗
PubMed2003

Mycophenolate mofetil prevents a clinical relapse in patients with systemic lupus erythematosus at risk.

BACKGROUND: Systemic lupus erythematosus (SLE) is characterised by the presence of antibodies to double stranded DNA (dsDNA), which are involved in the pathogenesis of SLE. Previous studies showed that at least two thirds of patients develop a clinical relapse within six months after a significant rise in the anti-dsDNA level, and most relapses were prevented by the administration of corticosteroids at the time of the rise. OBJECTIVE: To determine whether mofetil mycophenolate (MMF) can prevent a clinical relapse without the side effects associated with corticosteroids. METHODS: 36 patients with SLE were examined monthly to determine whether a rise in anti-dsDNA level had occurred. A rise was defined as an increase of 25% of the level of the previous sample of at least 15 IU/ml within a four month period. After a rise patients were treated with MMF 2000 mg daily for six months. Patients were monitored monthly for the occurrence of a clinical relapse and to assess the serological activity and state of activation of CD4+, CD8+, and CD19+ lymphocyte subsets. RESULTS: Anti-dsDNA rose in 10 patients. Treatment with MMF was started in all these patients, and after six months no clinical relapse had occurred. Side effects were minimal. Antibodies to dsDNA decreased during the treatment (p<0.001), associated with a decrease in the state of activation of CD19+ lymphocytes. No changes were found in the state of activation of CD4+ or CD8+ lymphocyte subsets. CONCLUSION: Administration of MMF after a rise in antibodies to dsDNA is well tolerated, decreases anti-dsDNA and B cell activation, and seems to prevent the occurrence of a clinical relapse in patients with SLE.

Adult↗
PubMed2002

Expression of recombinant proteinase 3, the autoantigen in Wegener's granulomatosis, in insect cells.

Proteinase 3 (PR3) is the major autoantigen for anti-neutrophil cytoplasmic antibodies (ANCA) in patients with Wegener's granulomatosis. Little is known about the major antigenic sites on PR3. To facilitate epitope mapping, PR3 was cloned in insect cells using a baculovirus expression system. Four different sequences of the PR3 cDNA were amplified by PCR: two clones containing the pro-peptide of PR3 with or without a His-tag (rproPR3-his and rproPR3, respectively) and two clones without the pro-peptide and with or without a His-tag (rPR3-his and rPR3, respectively). The PR3 sequences were cloned behind the polyhedrin promoter and the honeybee melittin signal peptide enabling secretion of rPR3. Plasmids were transposed into the genome of baculovirus, and wild types as well as PR3-containing virus genomes were transfected into Sf21 insect cells. All four rPR3 variants were secreted into the medium and were recognized by anti-neutrophil PR3 rabbit serum and by at least two anti-PR3 monoclonal antibodies. Mature forms of PR3 were recognized by almost all patient sera, whereas the pro-forms of PR3 were recognized by 14 of 18 PR3-ANCA sera tested. On SDS-PAGE, the four rPR3 forms migrated at approximately 32 kDa. RPR3-his and rproPR3-his could be purified by means of this His-tag. In conclusion, especially the mature rPR3s are well recognized by PR3-ANCA sera. The presence of a C-terminal His-tag facilitated purification of His-tagged rPR3. Thus, rPR3 expressed in insect cells can be used as a tool for diagnostic tests as well as for epitope mapping studies.

Animals↗
PubMed2002

In vitro cytokine production and proliferation of T cells from patients with anti-proteinase 3- and antimyeloperoxidase-associated vasculitis, in response to proteinase 3 and myeloperoxidase.

OBJECTIVE: To investigate in vitro proliferative responses of CD4+ T cells and generation of specific cytokines induced by stimulation of peripheral blood mononuclear cells (PBMCs) from patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis with the autoantigens proteinase 3 (PR3) and myeloperoxidase (MPO). METHODS: PBMCs from vasculitis patients with PR3 ANCA or MPO ANCA and from healthy controls were stimulated for 7 days with PR3, MPO, or control stimuli. Proliferation of CD4+ T cells was assessed by flow cytometry, using the proliferation marker Ki-67. Levels of the pro-proliferative cytokines interleukin-2 (IL-2) and IL-6 and of the Th1 and Th2 cytokines interferon-gamma (IFN gamma) and IL-10 in culture supernatants were determined. RESULTS: PR3 and MPO induced proliferative responses in CD4+ T cells from individual patients with ANCA-associated vasculitides and healthy controls in vitro. Neither PR3 nor MPO elicited significant IL-2 production. Levels of IL-6 were highest after stimulation with PR3 but low after stimulation with MPO, independent of study group. Stimulation with PR3, and to a lesser extent with MPO, induced a Th2 cytokine milieu, characterized by high production of IL-6 and IL-10 and low production of IFN gamma in patients and controls. CONCLUSION: PR3 and MPO promote proliferation of CD4+ T cells from patients with ANCA-associated vasculitides, but also cross-stimulate T cells from healthy individuals. Strong IL-10 production elicited by PR3 in vitro may act as an inhibitory signal for T cell proliferation and may have an important immunoregulatory function in vivo.

Adult↗
PubMed2002

Interference of PR3-ANCA with the enzymatic activity of PR3: differences in patients during active disease or remission of Wegener's granulomatosis.

Anti-neutrophil cytoplasmic antibodies (ANCA) against proteinase 3 (PR3) are strongly associated with Wegener's granulomatosis (WG) and are thought to be involved in its pathogenesis. Levels of PR3-ANCA do not always correspond to clinical disease activity. To investigate the relationship between functional effects of PR3-ANCA and disease activity, we tested the effect of IgG samples from sera of 43 WG patients, taken during active disease or remission, for their capacity to interfere with the proteolytic activity of PR3. Furthermore, longitudinal sera of seven WG patients were included. The enzymatic activity of PR3 was determined (1) with casein or with a small synthetic substrate and (2) by complexation of PR3 with alpha1-antitrypsin (alpha1-AT). With a fixed concentration (100 microg/ml) of IgG, PR3-ANCA from patients during an active phase of WG had a higher inhibitory capacity towards the proteolytic activity of PR3 and complexation of PR3 with alpha1-AT than did PR3-ANCA from WG patients during remission. However, the number of PR3-ANCA units that gave 50% inhibition of the PR3 enzymatic activity and its complexation with alpha1-AT was lower for patients during remission than for patients during an active phase of WG, indicating a stronger inhibitory capacity at a molar base. In conclusion, PR3-ANCA from patients during remission had a relatively higher inhibitory capacity towards the enzymatic activity of PR3 than PR3-ANCA from patients during an active phase. This may indicate that during active disease the ANCA titre is increased, but the number of active ANCA molecules that recognize the enzyme-inhibiting epitopes is not increased.

Adult↗
PubMed2002

IgG subclass distribution of autoantibodies differs between renal and extra-renal relapses in patients with systemic lupus erythematosus.

BACKGROUND: IgG subclasses of autoantibodies differ in their potential to induce an inflammatory response as they interact differentially with complement and Fcgamma receptors. METHODS: The IgG subclass distribution of anti-nucleohistone and anti-dsDNA antibodies was analysed longitudinally in patients with systemic lupus erythematosus before and at the moment of an extra-renal (n=23) or a renal relapse (n=l7). Kidney biopsy specimens of patients with a renal relapse were analysed for IgG subclass deposition. RESULTS: IgG1 anti-nucleohistone and IgG1 anti-dsDNA antibodies were present in plasma of 39 out of 40 patients. At the moment of a relapse, IgG2 and IgG3 anti-nucleohistone and IgG2 anti-dsDNA antibodies were more frequently present in patients with renal disease compared with those with extra-renal disease. Increases in levels of IgG1 anti-dsDNA were observed in 10 out of 11 patients prior to a renal relapse but only 10 out of 22 patients with an extra-renal relapse (91 vs 45%, P=0.02). Rises in IgG2 anti-dsDNA occurred at an equally low rate prior to both renal and extra-renal relapses. A rise in IgG2 anti-nucleohistone antibodies preceded a renal relapse in eight of 11 patients and an extra-renal relapse in only four out of 22 patients (73 vs 18%, P=0.006). In kidney biopsies all IgG subclasses could be detected. IgG1 and IgG2 subclass antibodies to nucleohistone and to dsDNA are the predominant subclasses found in plasma of lupus patients with renal disease. CONCLUSIONS: The frequent occurrence of a rise in IgG2 anti-nucleohistone and IgG1 anti-dsDNA in patients prior to a renal relapse suggests that, besides IgG1 subclass autoantibodies, IgG2 subclass antibodies to nucleohistone have a particular pathophysiological role in lupus nephritis.

Adult↗
PubMed2002

Screening for amyloid in subcutaneous fat tissue of Egyptian patients with rheumatoid arthritis: clinical and laboratory characteristics.

OBJECTIVE: To screen for amyloid and to assess associated clinical and laboratory characteristics in Egyptian patients with rheumatoid arthritis (RA). METHODS: Abdominal subcutaneous fat aspirates were consecutively collected from 112 patients (103 women, nine men) having RA for five years or more. To detect amyloid, fat smears were stained with Congo red and the concentration of amyloid A protein in fat tissue was measured. Clinical, radiological, and laboratory characteristics of the patients were assessed. RESULTS: Amyloid was detected in eight (7%) of the fat smears stained with Congo red. Compared with the Congo red stain, the sensitivity for detecting amyloid by measurement of amyloid A protein in fat tissue was 75% and the specificity was 100%. The amount of amyloid found was small for both methods. The median disease duration of the eight amyloid patients was significantly longer (17 years) than that of the non-amyloid patients (10 years). Bronchopulmonary disease and constipation were more common, whereas proteinuria and chronic renal insufficiency were not. The number of swollen joints and the number of red blood cells were significantly lower in the amyloid group. CONCLUSIONS: Quantification of amyloid A protein and staining with Congo red are strongly concordant methods of screening for amyloid in fat tissue. The prevalence of amyloid in Egyptian patients with RA is 7%. Proteinuria is not a discriminating feature, whereas long disease duration, constipation, bronchopulmonary symptoms, and a moderate to low number of red blood cells may help to identify the arthritic patients with amyloid.

Adipose Tissue↗