Immunoelectrophoretic assay for synovial fluid C3 with correction for synovial fluid globulin

Complement System Inhibition Modulates the Inflammation Induced by the Venom of Premolis semirufa, an Amazon Rainforest Moth Caterpillar

The caterpillar of the Premolis semirufa moth, commonly called Pararama, is found in the Brazilian Amazon region. Contact with the hairs can cause a chronic inflammatory reaction, termed "pararamosis". To date, there is still no specific treatment for pararamosis. In this study, we used a whole human blood model to evaluate the involvement of the complement in the proinflammatory effects of P. semirufa hair extract, as well as the anti-inflammatory potential of complement inhibitors in this process. After treatment of blood samples with the P. semirufa hair extract, there was a significant increase in the generation of soluble terminal complement complex (sTCC) and anaphylatoxins (C3a, C4a, and C5a), as well as the production of the cytokines TNF-α and IL-17 and the chemokines IL-8, RANTES, MIG, MCP-1, and IP-10. The inhibition of C3 with compstatin significantly decreased IL-17, IL-8, RANTES, and MCP-1 production. However, the use of the C5aR1 antagonist PMX205 promoted a reduction in the production of IL-8 and RANTES. Moreover, compstatin decreased CD11b, C5aR1, and TLR2 expression induced by P. semirufa hair extract in granulocytes and CD11b, TLR4, and TLR2 in monocytes. When we incubated vascular endothelial cells with extract-treated human plasma, there was an increase in IL-8 and MCP-1 production, and compstatin was able to decrease the production of these chemokines. C5aR1 antagonism also decreased the production of MCP-1 in endothelial cells. Thus, these results indicate that the extract of the Pararama bristles activates the complement system and that this action contributes to the production of cytokines and chemokines, modulation of the expression of surface markers in leukocytes, and activation of endothelial cells.

Innate inflammation and resolution in acute gout

Acute gout is an inflammatory arthritis that is controlled by the innate arm of the immune response. Although the causative feature of gout has long been recognized, it is surprising that the cellular activities that underpin the initiation and resolution of acute gout remain poorly described. This review article summarizes what are currently thought to be the key cellular mechanisms at play during an inflammatory episode of acute gout. The emerging role of mononuclear phagocytes is highlighted as having a central role in both the initiation and resolution of acute gout, and the interplay between monocytes and other elements of the innate immune response, including neutrophils, and complement protein activation are discussed.

Circulating C3 is necessary and sufficient for induction of autoantibody-mediated arthritis in a mouse model

Objective

For the inflammation characteristic of rheumatoid arthritis, the relative contribution of mediators produced locally in the synovium versus those circulating systemically is unknown. Complement factor C3 is made in rheumatoid synovium and has been proposed to be a crucial driver of inflammation. The aim of this study was to test, in a mouse model of rheumatoid arthritis, whether C3 synthesized within the synovium is important in promoting inflammation.

Methods

Radiation bone marrow chimeras between normal and C3^−/− mice were constructed in order to generate animals that expressed or lacked expression of C3 only in hematopoietic cells. Parabiotic mice were made by surgically linking C3^−/− mice to irradiated wild-type mice to obtain animals having C3 only in the circulation. Arthritis was induced by injection of serum from arthritic K/BxN mice.

Results

In bone marrow chimeras, synthesis of C3 by radioresistant cells was necessary and sufficient to confer susceptibility to serum-transferred arthritis. Parabionts having C3 only in the circulation remained sensitive to arthritis induction, and the cartilage of these arthritic mice contained deposits of C3.

Conclusion

In a mouse model in which the alternative pathway of complement activation is critical to the induction of arthritis by autoantibodies, circulating C3 was necessary and sufficient for arthritis induction.

The value of synovial fluid assays in the diagnosis of joint disease: a literature survey

OBJECTIVE

To carry out a critical appraisal of the literature in an attempt to assess the current value of synovial fluid (SF) analysis in the diagnosis of joint disease.

METHODS

A literature search was undertaken using the Medline, Biomed, Bids, Pubmed, and Embase electronic databases using the keywords: synovial fluid (SF) analysis, SF crystals, joint sepsis, acute arthritis, and SF cell counts, cytology, biomarkers, and microbiology.

RESULTS

Publications fell into three main categories. Firstly, reports assessing the value of the three traditional assays (microbiology, white blood cell counts, and microscopy for pathogenic crystals). For these quality control evidence was found to be sparse, and tests for sensitivity, specificity, and reliability showed worrying variations. These poor standards in SF analysis may be due to lack of inclusion of some tests within routine pathology services. Secondly, claims for the usefulness of "new" assays (cytology and biochemical markers). For cytology, the supporting evidence was mainly anecdotal and there were no reports on specificity, sensitivity, and reliability. Interpretation difficulties are a major hindrance to the clinical use of biochemical assays, which remain primarily research tools. Finally, work on the diagnostic value of SF analysis in general. The appraisal confirmed that SF analysis remains of major diagnostic value in acute arthritis, where septic arthritis or crystal arthropathy is suspected, and in intercritical gout.

CONCLUSIONS

Given the importance of SF tests, rationalisation of their use, together with improved quality control, should be immediate priorities. Further investigation is recommended into the contribution of SF inspection and white cell counts to diagnosis, as well as of the specificity and sensitivity of SF microbiological assays, crystal identification, and cytology.

Relation between synovial fluid C3 degradation products and local joint inflammation in rheumatoid arthritis, osteoarthritis, and crystal associated arthropathy

C3 degradation products (C3dg/d) were estimated in 288 synovial fluid (SF) samples (rheumatoid arthritis (RA) 93, osteoarthritis (OA) 68, chronic pyrophosphate arthropathy 80, acute pseudogout 20, others 27) from knees of 138 patients (bilateral 67, serial sampling on two to six occasions 40). At each aspiration knees were defined as 'active' or 'inactive' by single observer global assessment using six clinical parameters of inflammation. Lack of correlation between paired SF and plasma C3dg/d implied local C3 activation within joints. Raised SF C3d levels were found in active compared with inactive RA joints (mean (range) 51 (15-105) and 6 (0-15) units/ml respectively). Low SF C3dg/d levels were found in OA (mean (range) 0.8 (0-7) units/ml) and chronic pyrophosphate arthropathy (mean (range) 4 (0-16) units/ml), irrespective of clinical activity. In contrast, very high levels (mean (range) 61 (16-126) units/ml) were present in all cases of pseudogout. These differences remained after correction for SF C3 or albumin. This study is the first to show a positive correlation between SF C3dg/d and local inflammation in RA joints. It further suggests that C3 activation is a constant feature of pseudogout but not an accompaniment of inflammation associated with chronic crystal associated synovitis or OA.

Elevated C3 anaphylatoxin levels in synovial fluids from patients with rheumatoid arthritis

Because cleavage products of the third component of complement augment inflammation and may contribute to arthritis, we used a competitive inhibition radioimmunoassay to measure levels of the low molecular weight cleavage products of the third component of complement, C3a and C3adesArg, in 72 synovial fluid samples. Mean levels of C3a/C3adesArg were more than sevenfold higher in 41 patients who had rheumatoid arthritis than in 15 patients who had degenerative joint disease or 5 patients who had traumatic arthritis. Striking elevations were also present in 2 patients who had acute gouty arthritis. A calculation of the fraction of intraarticular C3 cleaved showed that the patients with rheumatoid arthritis had a mean C3 cleavage of 11.6 +/- 11.0%, which was significantly higher than values of less than 1.5% for patients with degenerative joint disease or traumatic arthritis. In rheumatoid arthritis and gouty arthritis, specific immunoassay identified substantial quantities of the initial C3 cleavage fragments.

Activation of the alternative pathway of complement by monosodium urate monohydrate crystals and other inflammatory particles

Activation of serum C3 by monosodium urate monohydrate (MSU) crystals and other particles was determined by immunofixation following electrophoretic separation of C3 and its activation products. Densitometry allowed quantitation of results. MSU, hydroxyapatite, brushite, and calcium pyrophosphate dihydrate crystals split C3 under conditions which demonstrate activation via the alternative pathway (AP). Quantitatively similar results were obtained in immunoglobulin deficient serum. Activation was crystal specific and was reduced by heating, grinding, sonication, and aging of crystals. Other inflammatory particles (e.g., blackthorn) activated C3 via the AP: noninflammatory particles (e.g., diamond) caused insignificant activation. It is suggested that particle-induced activation of the alternative pathway of complement may be important in the initiation of crystal-induced synovitis.

Gout

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Proceedings of a symposium on crystal-related arthropathies. 22 October and 23 October, 1982, Bristol Polytechnic, Bristol

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In vitro effects of radiographic contrast media on the complement system

The effect of several radiographic contrast media on the complement system in vitro was examined using quantitative crossed immunoelectrophoresis. Diatrizoate, iothalamate, metrizoate, and methiodal did not cause electrophoretic conversion of C3 or properdin factor B. In fact, the small degree of spontaneous conversion occurring when serum is incubated in polypropylene tubes was inhibited by these contrast media or by hypertonic sodium chloride. Metrizamide caused enhanced conversion of C3 and factor B that was only partially inhibited by ethylene glycol tetracetic acid (EGTA) but completely inhibited by ethylenediaminetetraacetic acid (EDTA). Iodipamide caused a unique electrophoretic alteration of C3 that was not affected by EDTA or several other inhibitors and that was not identical with the usual products of C3 activation. Iodipamide in very low concentrations inhibited complement activation through the classical pathway.

Binding of immunoglobulin and activation of complement by asbestos fibers

Asbestos fibers adsorbed IgG from whole human serum in amounts comparable to that taken up by crystals of calcium pyrophosphate or hydroxyapatite, but less than that adsorbed by crystals of monosodium urate monohydrate. Chrysotile asbestos was much more active in binding IgG than was amphibole asbestos. The electrophoretic mobility of adsorbed IgG was a function of the surface charge of the crystal studied. Negatively charged fibers adsorbed cationic IgG, and positively charged fibers adsorbed anionic IgG. Complement activation by asbestos, as judged by electrophoretic conversion of C3, was similar for all fiber types tested. Properdin factor B was also activated in the presence of asbestos. Activation of both properdin factor B and C3 was only partially inhibited by ethylene glycol tetraacetic acid, demonstrating that activation was occurring through both the classical and alternative pathways.

C3 activation by monosodium urate monohydrate and other crystalline material

Monosodium urate monohydrate (MSUM) is a potent activator of the complement system as measured by electrophoretic conversion of beta1C to beta1A. Activation of C3 in human serum by MSUM is both time- and dose-dependent. The sensitivity of the assay allows detection of C3 activation by as little as 0.2 mg/ml of MSUM. It was observed that C3 activation is calcium dependent and elimination by both EDTA and EGTA, a finding that demonstrated the major role of the classic pathway of complement activation. Excess calcium or magnesium alone inhibited C3 activation by MSUM in accord with the inhibitory effect of these cations on sensitized sheep cell hemolysis by complement. Heating of MSUM at 200 degrees C for 2 hours removes the water of crystallization such that heated crystals may no longer be considered MSUM. Such treatment has a variable effect on C3 activation. Of the crystals and other material studied, only zymosan was more potent than MSUM in activating C3. Calcium prophosphate dihydrate and hydroxyapatite activated significant amounts of C3. Asbestos, glass wool, or a variety of microcrystalline steroids activated little or no C3.