Enhanced liver fibrosis test in patients with psoriasis, psoriatic arthritis and rheumatoid arthritis: a cross-sectional comparison with procollagen-3 N-terminal peptide (P3NP).

BACKGROUND: The enhanced liver fibrosis (ELF) test has been introduced to screen, diagnose and/or monitor liver conditions in large groups of patients with liver diseases. It has not been used in inflammatory skin or joint diseases. OBJECTIVES: To evaluate the distribution of the ELF test, apply existing cut-offs for hepatic patients and healthy controls, and compare it with the procollagen-3 N-terminal peptide (P3NP) test in patients with psoriasis (PSO), psoriatic arthritis (PsA) and rheumatoid arthritis (RA), and controls. METHODS: In total, 531 patients were included. Demographic, lifestyle and disease-specific data were collected. ELF and P3NP tests were performed. RESULTS: Prevalence of an increased ELF score (> 11) and P3NP was highest in patients with RA (7·7% and 6·1%, respectively) followed by patients with PSO (1·7% and 5·2%, respectively) and PsA (0·7% and 1·3%, respectively). Mean ± SD ELF scores for PSO, PsA and RA were, respectively, 9·09 ± 0·86, 8·96 ± 0·76 and 9·55 ± 1·04. All subgroups with moderate-to-severe disease severity had higher (> 9·8) ELF scores (PSO 27·0% vs. 18·3%; PsA 19·2% vs. 12%; RA 45·8% vs. 30·5%) and P3NP values. Distribution of the ELF score was smaller than the P3NP value [mean ± SD: 9·15 ± 0·92 (range 6·53-13·05) vs. 8·37 ± 4·30 (range 0·53-63·88)]. CONCLUSIONS: ELF score and P3NP are elevated in PSO, PsA and RA. ELF may be superior to P3NP alone, but further research should be done to validate the ELF test in determining susceptibility for developing liver fibrosis in PSO, PsA and RA.

Proximal fractures of the humerus in patients older than 75 years of age: should we consider operative treatment?

BACKGROUND: Over 75 % of patients presenting with a proximal humerus fracture are 70 years or older. Very little is known about the outcome after operative treatment of these fractures in very old patients. This study was performed to gain more insight in safety and functional outcome of surgical treatment of proximal humerus fractures in the elderly. MATERIALS AND METHODS: In this observational study, we analyzed all operatively treated patients, aged 75 or older, with a proximal humerus fracture between January 2003 and December 2008 in our center. Patient selection was on clinical grounds, based on physical, mental, and social criteria. Complications were evaluated. We used the DASH Questionnaire to investigate functional outcome, pain, and ADL limitations. RESULTS: Sixty-four patients were treated surgically for a displaced proximal fracture of the humerus: 15 two-part, 32 three-part, and 17 four-part fractures. Mean DASH scores were 37.5, 36.9, and 48.6, respectively. Regarding the operative methods, overall good results were obtained with the modern locked plate osteosynthesis (mean DASH 34.4). Prosthetic treatment, mostly used in highly comminuted fractures, often resulted in poor function (mean DASH 72.9). Persistent pain and ADL limitations were more present in more comminuted fractures (64 and 50 % in patients with 4-part fractures vs. 14 % in 2-part fractures). There were no postoperative deaths within 3 months of surgery, and fracture-related and non-fracture-related complication rates were low (non-union 3 %; 1 myocardial infarction). CONCLUSION: This study shows that it is safe and justifiable to consider surgical treatment of a severely dislocated proximal humerus fracture in selected patients aged 75 and older. LEVEL OF EVIDENCE: According to OCEBM Working Group,Level IV.

Markers of systemic inflammation in psoriasis: a systematic review and meta-analysis.

Studies investigating systemic inflammation in psoriasis use different serum markers and report discrepant results. We set out to determine whether systemic inflammation is elevated in patients with psoriasis compared with healthy controls, and to measure the extent of this elevation, by summarizing available data on serum inflammatory markers. PubMed, Embase and Web of Science were searched from inception to March 2011. We included studies comparing the serum inflammatory markers interleukin (IL)-1ß, IL-6, IL-10, C-reactive protein (CRP), intracellular adhesion molecule (ICAM)-1, E-selectin and tumour necrosis factor (TNF)-α in patients with psoriasis and healthy controls. Differences in serum marker levels between patients and controls were pooled as standardized mean differences (SMDs; Cohen's d) using a random-effects model. Seventy-eight studies were eligible. Of the 7852 individuals included, 3085 had (severe plaque) psoriasis. The pooled SMDs were higher in patients with psoriasis than in healthy controls for IL-6 [d = 1·32, 95% confidence interval (CI) 0·83-1·81], CRP (d = 1·83, 95% CI 0·76-2·90), TNF-α (d = 1·32, 95% CI 0·86-1·79), E-selectin (d = 1·78, 95% CI 1·32-2·25) and ICAM-1 (d = 1·77, 95% CI 1·15-2·39). The SMD between cases and controls for IL-1ß and IL-10 was not significant. Age had a significant effect on the SMD for IL-6 and TNF-α. For IL-6 the effect size was higher for plaque psoriasis studies (d = 1·98). The effect size was not influenced by the Psoriasis Area and Severity Index, measurement method or quality assessment. The pooled analyses suggest modest but significantly elevated levels of the proinflammatory cytokines in the serum of patients with psoriasis with predominantly severe disease. To what extent this modest increment is clinically relevant could be investigated in a synthesis of all studies measuring inflammation before and after antipsoriatic therapy.

[Focal epithelial hyperplasia of the oral mucosa. A unique manifestation of human papillomavirus]. / Focale epitheliale hyperplasie van het mondslijmvlies. Een unieke manifestatie van het humaanpapillomavirus.

A 34-year old Creole woman appeared at the dermatology department with white-pink spots on the oral mucosa, which had been there for some time. Histology showed lesions characteristic of focal epithelial hyperplasia. The patient was treated with a CO2 laser. Focal epithelial hyperplasia is a rare benign lesion and is caused by human papillomavirus subtypes 13 or 32; it only appears on the oral mucosa.

Association of smoking with the constitution of the anti-cyclic citrullinated peptide response in the absence of HLA-DRB1 shared epitope alleles.

OBJECTIVE: Smoking is a risk factor for anti-cyclic citrullinated peptide (anti-CCP) antibody-positive rheumatoid arthritis (RA) in patients with HLA-DRB1 shared epitope (SE) alleles. It is unknown whether smoking influences not only the presence of these antibodies, but also other characteristics of the anti-CCP response, such as isotype usage. The aim of this study was to determine the influence of smoking on anti-CCP isotypes in RA patients, and to determine whether this influence is observed in the presence and/or absence of SE alleles. METHODS: IgA, IgM, and IgG subclasses of anti-CCP antibodies were measured by enzyme-linked immunosorbent assay in serum obtained at the first visit to the Leiden Early Arthritis Clinic from 216 patients with anti-CCP-positive RA whose smoking habits were also assessed. HLA genotyping data were available for 202 of these patients. RESULTS: IgA and IgM anti-CCP were more frequent in RA patients who were smokers than in those who were nonsmokers (odds ratio 2.8 and 1.8, respectively). In addition, levels of all isotypes of anti-CCP, except IgG3, were significantly higher (P < 0.05) in smokers. The number of anti-CCP isotypes was higher in smokers compared with nonsmokers, both in SE-negative RA (P = 0.04) and in SE-positive RA (P = 0.07). CONCLUSION: Patients with anti-CCP-positive RA who have a current or former tobacco exposure display a more extensive anti-CCP isotype usage in general, and IgA and IgM in particular, compared with patients with anti-CCP-positive RA who have never smoked. In contrast to its influence on the incidence of anti-CCP positivity, the influence of tobacco exposure on the constitution of the anti-CCP response is significant in SE-negative RA. These findings suggest a differential effect of tobacco exposure on the induction as compared with the propagation of the anti-CCP antibody response.

Isotype distribution of anti-cyclic citrullinated peptide antibodies in undifferentiated arthritis and rheumatoid arthritis reflects an ongoing immune response.

OBJECTIVE: The evolution of the rheumatoid arthritis (RA)-specific anti-cyclic citrullinated peptide (anti-CCP) antibody response, as measured by the isotypes of anti-CCP, has not been described. This study was undertaken to determine anti-CCP isotype usage in patients with undifferentiated arthritis (UA), patients with recent-onset RA, and patients with RA of long duration. METHODS: IgA, IgM, and IgG subclasses of anti-CCP were measured by enzyme-linked immunosorbent assay in serum samples that were obtained from IgG anti-CCP antibody-positive patients with UA (n = 110) and IgG anti-CCP antibody-positive patients with RA (n = 152) early after the onset of arthritis. Patients with UA in whom RA developed within 1 year (UA-->RA) were compared with patients with UA in whom RA did not develop within 1 year (UA-->UA). In addition, baseline serum samples obtained from a subset of patients with RA (n = 64) were compared with sera obtained from the same patients a median of 7 years later. RESULTS: IgM anti-CCP was present in early samples from both patients with UA and patients with RA and in followup samples from patients with RA. Several IgG anti-CCP antibody-positive patients who did not have IgM anti-CCP early after disease onset did display IgM anti-CCP later in the course of the arthritis. A diverse pattern of isotype usage was detected in early samples, with a trend toward lower frequencies of all isotypes of anti-CCP in patients with UA compared with patients with RA and in UA-->UA patients compared with UA-->RA patients. Levels of all isotypes except IgG1 had decreased after 7 years. CONCLUSION: These data indicate development of the anti-CCP isotype repertoire into full usage early in the course of arthritis. The sustained presence of IgM anti-CCP indicates ongoing recruitment of new B cells into the anti-CCP response, reflecting a continuous (re)activation of the RA-specific anti-CCP response during the course of anti-CCP-positive arthritis.

Displacement of linker for activation of T cells from the plasma membrane due to redox balance alterations results in hyporesponsiveness of synovial fluid T lymphocytes in rheumatoid arthritis.

The T lymphocytes that reside in the synovium of the inflamed joints in patients with rheumatoid arthritis display severe hyporesponsiveness upon antigenic stimulation, which is probably due to their constant subjection to high levels of oxidative stress. Here we report that the synovial fluid T lymphocytes exert severely impaired phosphorylation of the adaptor protein linker for activation of T cells (LAT), a crucial component of the TCR-mediated signaling pathways. In healthy T lymphocytes, LAT is a membrane-bound protein and becomes phosphorylated by zeta-associated protein of 70 kDa (ZAP-70) upon TCR engagement. The molecular basis underlying the deficient phosphorylation of LAT and consequently the hyporesponsiveness of the synovial fluid T lymphocytes lies in the membrane displacement of LAT. We demonstrate that the subcellular localization of LAT is sensitive to changes in the intracellular levels of the antioxidant glutathione. The membrane anchorage of LAT, and consequently the phosphorylation of LAT and the cellular activation of the synovial fluid T lymphocytes upon TCR engagement, is restored in synovial fluid T lymphocytes after supplementation of the intracellular glutathione levels with N-acetyl-l -cysteine. These data suggest a role for the membrane displacement of LAT in the hyporesponsiveness of the synovial fluid T lymphocytes as a consequence of oxidative stress.

Expression of the thioredoxin-thioredoxin reductase system in the inflamed joints of patients with rheumatoid arthritis.

OBJECTIVE: To examine the expression of the thioredoxin (TRX)-thioredoxin reductase (TR) system in patients with rheumatoid arthritis (RA) and patients with other rheumatic diseases. METHODS: Levels of TRX in plasma and synovial fluid (SF) were measured using enzyme-linked immunosorbent assay. Cellular distribution of TRX was determined by flow cytometry and histochemistry. Cellular expression of TR was studied by in situ messenger RNA (mRNA) hybridization. The effect of oxidative stress and tumor necrosis factor alpha (TNF alpha) on TRX expression by cultured rheumatoid fibroblast-like synoviocytes was studied. RESULTS: Significantly increased TRX levels were found in the SF from 22 patients with RA, when compared with plasma levels in the same patients (P < 0.001) and compared with SF TRX levels in 15 patients with osteoarthritis (P < 0.001), 13 patients with gout (P < 0.05), and 9 patients with reactive arthritis (P < 0.0001). The presence of TRX could be demonstrated within the SF-derived mononuclear cells and synovial tissue (ST) of RA patients. Concordantly, expression of TR mRNA was observed in the ST of these patients. Stimulation of synovial fibroblast-like synoviocytes with either H2O2 or TNF alpha induced an increase in the production of TRX. CONCLUSION: The data demonstrate significantly increased concentrations of TRX in the SF and ST of RA patients when compared with the levels in patients with other joint diseases. Evidence is presented that the local environment in the rheumatic joint contributes to increased TRX production. Based on its growth-promoting and cytokine-like properties, it is proposed that increased expression of TRX contributes to the disease activity in RA.

CD28 co-stimulation is intact and contributes to prolonged ex vivo survival of hyporesponsive synovial fluid T cells in rheumatoid arthritis.

In rheumatoid arthritis (RA), T cells in the inflamed joint are considered to play a crucial role in the pathogenesis. However, despite the fact that synovial T cells have an activated memory phenotype, they are functionally suppressed upon combined CD3 and CD28 stimulation. Here, we analyzed the contribution of both CD3 and CD28 to the hyporesponsiveness of synovial T cells in RA. In contrast to the low CD3 responsiveness of synovial fluid (SF) T cells compared to peripheral blood (PB) T cells, the CD28 co-stimulatory response was observed to be unaffected. Hyporesponsiveness of SF T cells has previously been associated with decreased levels of intracellular glutathione (GSH), an antioxidant and regulator of the intracellular redox state. Treatment of SF T cells with N-acetylcysteine, an antioxidant and replenisher of GSH, selectively improved CD3-induced responses, while leaving CD28 responsiveness unaffected. These data show that the CD3 pathway is highly sensitive to intracellular GSH alterations, whereas CD28 responsiveness is relatively refractory. Furthermore, in support for a functional role of CD28 co-stimulation, it was demonstrated that CD28 ligation acted in synergy with the IL-2 receptor gamma chain signaling cytokine IL-15 in the enhancement of the ex vivo survival of SF T cells. These data indicate that CD28 co-stimulatory capacity of SF T cells, in contrast to CD3 stimulation, remains intact despite an altered intracellular redox state. Thereby, CD28 stimulation may contribute to the persistence of T cells at the site of inflammation, which might be of relevance in the pathogenesis of RA.

Evidence for the role of an altered redox state in hyporesponsiveness of synovial T cells in rheumatoid arthritis.

In rheumatoid arthritis (RA), T cells isolated from the synovial fluid (SF) show impaired responses to mitogenic stimulation compared with T cells from the peripheral blood (PB). Here it is reported that hyporesponsiveness of SF T cells correlated with a significant decrease in the levels of the intracellular redox-regulating agent glutathione (GSH). GSH was decreased in both CD4+ (p = 0.0022) and CD8+ (p = 0.0010) SF T cell subsets compared with PB CD4+ and CD8+ T cells in RA patients. Levels of thioredoxin (TRX), another key redox mediator, previously found to be secreted under conditions of oxidative stress, were found to be significantly increased in SF compared with plasma samples of RA patients (p = 0.005). Increased levels of TRX in the SF of inflamed joints was found to be associated with RA when compared with other arthritides (p = 0.007). Restoration of GSH levels in SF T cells with N-acetyl-L-cysteine (NAC), enhanced mitogenic induced proliferative responses and IL-2 production. Collectively, these data impute an important role to an altered redox state in the hyporesponsiveness of joint T cells in patients with RA.

Changes in antibodies to C1q predict renal relapses in systemic lupus erythematosus.

The presence of elevated plasma levels of autoantibodies against C1q, a subcomponent of the first component of complement in sera of patients with systemic lupus erythematosus (SLE) has been found to be associated with renal involvement. The purpose of this study was to determine whether increases in anti-C1q antibodies (anti-C1q) precede renal involvement in SLE. Forty-three SLE patients were studied longitudinally to determine the relationship between manifestations of the disease and levels of anti-C1q as well as to identify antibodies against double-stranded DNA (anti-dsDNA). Increased levels of anti-C1q were detected in all 14 of the patients who developed proliferative lupus nephritis out of 17 patients with renal relapses, which was significantly more frequent (P < 0.005) than in patients with nonrenal relapses (six of 16 patients) or with inactive disease (two of 10 patients). Increased anti-dsDNA levels were observed in 14 of 17 patients with renal relapses compared with 15 of 16 patients with nonrenal relapses and five of 10 patients with inactive disease. Significant increases in anti-C1q levels prior to the relapse occurred in 10 of 14 patients who developed proliferative nephritis and in three of 16 patients with nonrenal relapses. Significant increases in anti-dsDNA levels occurred in 11 patients of the former group and in nine patients of the latter group. No significant increases in anti-C1q or anti-dsDNA levels were observed in the patients with inactive disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Subclass distribution of IgA and IgG antibodies against Clq in patients with rheumatic diseases.

To obtain insight into the immunoregulatory mechanisms in patients with different rheumatic diseases, the occurrence and the subclass distribution of IgA and IgG antibodies against Clq (anti-ClqAb) was determined. In patients with systemic lupus erythaematosus (SLE) the highest frequency of increased serum levels of IgG anti-ClqAb were found, whereas IgA anti-ClqAb were predominantly present in patients with ankylosing spondylitis (AS) and patients with rheumatoid arthritis complicated by vasculitis (RV). In all the IgA anti-ClqAb positive AS and RV patients the antibody reactivity involved the IgA1 subclass while the IgA2 subclass was found in 47% of the patients. Further characterization of the IgA anti-Clq binding activity in sera of AS patients revealed that both subclasses of IgA anti-ClqAb were predominantly polymeric; the binding of both IgA subclasses with solid phase Clq was inhibitable by aggregated fluid phase Clq; we found no detectable interference of rheumatoid factor in the test system for the measurement of IgA anti-ClqAb. In patients with SLE the IgG anti-ClqAb reactivity was mainly of the IgG2 and IgG3 subclass, whereas in the same patients the IgG anti-tetanus toxoid response was not restricted to these subclasses. The predominance of IgG2 and IgG3 subclass of anti-ClqAb in sera of SLE patients, suggests a skewing of the anti-ClqAb response. The observation that the IgA anti-ClqAb of both subclasses is predominantly polymeric in nature and the notion that polymeric IgA is associated with activation of inflammation cascades, suggests that IgA anti-ClqAb may contribute to tissue damage.

Role of liver endothelial and Kupffer cells in clearance of human C1q in rats.

In the present study the contribution of rat liver endothelial cells (EC) and Kupffer cells (KC) in the clearance of human (hu) C1q in rats was investigated. In untreated rats and rats depleted from KC the clearance kinetics and the tissue distribution of hu C1q were measured. In untreated rats, the clearance of hu C1q occurred in a monophasic manner with a half-life of 66 +/- 26.7 min. The clearance of hu C1q in KC-depleted rats was delayed significantly (p < 0.001) and occurred with a half-life of 217 +/- 78.8 min. Fifteen min after injection, 11 +/- 3.5% of hu C1q was found in the liver of untreated rats and 8 +/- 1.4% was found in the liver of KC-depleted rats. The percentage non-trichloroacetic acid precipitable activity in the circulation, as a measure for degradation of C1q, reached a level of 11.6 +/- 5.6% at 240 min in untreated rats compared with 4.6 +/- 5.8% in KC-depleted rats. Double immunofluorescence staining 5 min after administration of C1q in untreated rats, revealed that C1q was associated with KC and EC in the liver. Fifteen minutes after i.v. injection of hu C1q, there was an uptake of C1q in the hepatocytes. In KC-depleted rats, 5 min after administration of hu C1q, C1q was bound to the EC. Fifteen minutes after injection, C1q was also found in the hepatocytes. Electron microscopical studies revealed that C1q binds to EC, and that it is internalized in the hepatocytes and KC. The clearance of hu C1q in untreated rats was inhibited by preadministration of high concentrations of bovine C1q. These data show that rats depleted from KC are able to bind, internalize and degrade C1q, and that EC may play a role in the handling of C1q and C1q bound to immune complexes.

The relationship between serum titers of autoantibodies to C1q and age in the general population and in patients with systemic lupus erythematosus.

The aim of the present study was to assess the relationship between age and titers of autoantibodies to C1q (C1qAb) in individuals randomly selected out of the general population and in systemic lupus erythematosus (SLE) patients. Serum samples of 659 randomly selected individuals and 169 SLE patients were divided into 6 age groups from 20 to 79 years. IgG and IgA C1qAb titers were measured by ELISA. The highest titers of IgG and IgA C1qAb in sera of randomly selected individuals were found in the oldest age groups. In serum of SLE patients the highest titers of IgG C1qAb were found in the youngest age groups, whereas IgA C1qAb titers did not change with aging. It is concluded that the distribution pattern of IgG and IgA C1qAb titers in serum of individuals randomly selected out of the general population is similar to that of other autoantibodies. The increased titers of IgG C1qAb in serum of young patients with SLE suggest a role of these antibodies in the pathogenesis of the disease.

Autoantibodies to neutrophil cytoplasmic enzymes in Felty's syndrome.

In this study we determined the occurrence of anti-neutrophil cytoplasmic antibodies (ANCA) and the specificity of these antibodies (Ab) in the serum of patients with Felty's syndrome (FS) and in serum of patients with uncomplicated rheumatoid arthritis (RA). ANCA, detected by indirect immunofluorescence on ethanol-fixed neutrophils, was found in 77% of 30 patients with FS and in 36% of 50 RA patients. Ab against lactoferrin (LF) occurred more frequently in FS patients (50%) than in RA patients (4%), whereas reactivity against the other cytoplasmic antigens tested (proteinase-3, myeloperoxidase and elastase) did not differ significantly between these patient groups. The specific reactivity of FS sera with LF was established by demonstrating that the Ab reactivity resided in IgG, was located in the F(ab')2 fragments and could be inhibited from binding to the ELISA plate-bound LF by purified LF in the fluid phase. These results demonstrate that anti-LF Ab occur in FS and suggest that the detection of anti-LF Ab in patients with FS may be useful in the diagnosis of FS.

Anti-lactoferrin antibodies in patients with rheumatoid arthritis with vasculitis.

Anti-lactoferrin antibodies (anti-LF Ab) are more frequently found in patients with rheumatoid arthritis (RA) complicated by vasculitis when compared to patients with uncomplicated RA. Therefore the detection of anti-LF Ab in serum of patients with RA may be useful in the diagnosis of vasculitis in RA patients.

Antilactoferrin antibodies in patients with rheumatoid arthritis are associated with vasculitis.

OBJECTIVE: To determine the occurrence of antineutrophil cytoplasmic antibodies (ANCA) and the specificity of these antibodies (Ab) in serum from patients with rheumatoid arthritis (RA) and patients with rheumatoid arthritis complicated by vasculitis (rheumatoid vasculitis [RV]). METHODS: ANCA was detected with an indirect immunofluorescence test on ethanol-fixed granulocytes. Ab against the cytoplasmic antigens proteinase-3, elastase, lactoferrin (LF), and myeloperoxidase were measured by enzyme-linked immunosorbent assay. RESULTS: ANCA were found in the serum of 43% of 49 patients with RV and in 36% of 50 patients with RA. Anti-LF Ab occurred more frequently in RV patients (45%) than in RA patients (4%), whereas reactivity against the other cytoplasmic antigens did not differe significantly between these groups. CONCLUSION: Anti-LF Ab in serum of patients with RA may be useful in the diagnosis of vasculitis in RA.

Clinical significance of rheumatoid factors in early rheumatoid arthritis: results of a follow up study.

Serum rheumatoid factors (RF) were measured yearly in 135 women with rheumatoid arthritis by the Waaler-Rose and latex fixation tests and IgM, IgA, and IgG RF were measured by enzyme linked immunosorbent assays (ELISAs). The patients were followed up from an early phase of the disease for a mean duration of six years. Patients with a persistently positive RF test, irrespective of the type of test used, had more radiological abnormalities, more disease activity, worse functional ability, more extra-articular manifestations, and needed more treatment with second line drugs than patients with persistently negative or variably positive and negative test results during the follow up. Increased RF levels, especially a high level of IgA RF within three years of the onset of symptoms, was prognostic for a more severe disease outcome six years after the onset of symptoms.

Antibodies against C1q in anti-glomerular basement membrane nephritis.

The prevalence of antibodies against the collagen-like region of the subcomponent of the first component of complement, C1q, was investigated in 11 patients with anti-glomerular basement membrane (GBM) nephritis. Anti-C1q antibodies (anti-C1qAb) were detected in seven patients. IgG anti-C1qAb were found in four and IgA anti-C1qAb in five patients. During follow up of the patients a relationship was observed between the levels of IgG anti-C1qAb and the levels of anti-GBM antibodies (anti-GBMAb). Gelfiltration experiments indicated that both IgG anti-C1qAb as well as IgG anti-GBMAb were monomeric and that binding also occurred with the F(ab')2 fragments of the antibodies. Although anti-C1qAb and anti-GBMAb are both directed against a collagen-like structure, it was demonstrated by means of inhibition experiments that anti-C1qAb and anti-GBMAb are directed against different antigenic sites. Comparison of patients with anti-GBM nephritis with and without anti-C1qAb revealed that there were no differences in disease activity or disease severity. Therefore, the results of this study suggest that anti-C1qAb do not play a direct pathogenetic role in anti-GBM nephritis.

IgG autoantibodies to C1q do not detectably influence complement activation in vivo and in vitro in systemic lupus erythematosus.

The influence of IgG antibodies to C1q (C1qAb) on activation of the classical pathway of the complement system was investigated in patients with systemic lupus erythematosus (SLE). In in vivo experiments, a prototype for immune complexes was administered intravenously to 14 patients and 9 healthy controls. Eight SLE patients had increased C1qAb titers. The increase of C3a levels, which was measured as a parameter of C1 activation, was significantly lower in SLE patients than in the healthy controls (p = 0.01). No correlation was found between C3a increases and C1qAb titers. In in vitro experiments the influence on C1 activation of monomeric IgG isolated from serum of 11 SLE patients, 7 of whom had increased C1qAb titers, was measured in a C4 consumption assay. The presence of C1qAb did not influence C4 consumption. The results demonstrate that C1qAb do not influence C1 activation by immune complexes in SLE patients.