Complement components and their activation products in pleural fluid

Thoracic Involvement in Systemic Autoimmune Rheumatic Diseases: Pathogenesis and Management

Thoracic involvement is one of the main determinants of morbidity and mortality in patients with autoimmune rheumatic diseases (ARDs), with different prevalence and manifestations according to the underlying disease. Interstitial lung disease (ILD) is the most common pulmonary complication, particularly in patients with systemic sclerosis (SSc), idiopathic inflammatory myopathies (IIMs) and rheumatoid arthritis (RA). Other thoracic manifestations include pulmonary arterial hypertension (PAH), mostly in patients with SSc, airway disease, mainly in RA, and pleural involvement, which is common in systemic lupus erythematosus and RA, but rare in other ARDs.In this review, we summarize and critically discuss the current knowledge on thoracic involvement in ARDs, with emphasis on disease pathogenesis and management. Immunosuppression is the mainstay of therapy, particularly for ARDs-ILD, but it should be reserved to patients with clinically significant disease or at risk of progressive disease. Therefore, a thorough, multidisciplinary assessment to determine disease activity and degree of impairment is required to optimize patient management. Nevertheless, the management of thoracic involvement-particularly ILD-is challenging due to the heterogeneity of disease pathogenesis, the variety of patterns of interstitial pneumonia and the paucity of randomized controlled clinical trials of pharmacological intervention. Further studies are needed to better understand the pathogenesis of these conditions, which in turn is instrumental to the development of more efficacious therapies.

ANA positivity and complement level in pleural fluid are potential diagnostic markers in discriminating lupus pleuritis from pleural effusion of other aetiologies

OBJECTIVE

Lupus pleuritis is the most common pulmonary manifestation of systemic lupus erythematosus (SLE). We aimed to compare various biomarkers in discriminating between pleural effusions due to lupus pleuritis and other aetiologies.

METHODS

We determined in 59 patients (16 patients with SLE and 43 patients without SLE) pleural fluid levels of high-mobility group box 1, soluble receptor for advanced glycation end products (sRAGE), adenosine deaminase (ADA), interleukin (IL) 17A, tumour necrosis factor-α, antinuclear antibodies (ANA), and complements C3 and C4.

RESULTS

We found significant differences in the pleural fluid level of sRAGE, ADA, IL-17A, C3 and C4, and in the proportion of ANA positivity, among lupus pleuritis and other groups with pleural effusion. Specifically, ANA positivity (titre ≥1: 80) achieved a high sensitivity of 91%, specificity of 83% and negative predictive value (NPV) of 97% in discriminating lupus pleuritis from non-lupus pleural effusion. A parallel combination of the level of C3 (<24 mg/dL) and C4 (<3 mg/dL) achieved a sensitivity of 82%, specificity of 89% and NPV of 93% in discriminating lupus pleuritis from non-lupus exudative pleural effusion.

CONCLUSIONS

In conclusion, ANA, C3 and C4 in pleural fluid are useful in discriminating lupus pleuritis from pleural effusion due to other aetiologies with high NPV.

Soluble Membrane Attack Complex: Biochemistry and Immunobiology

The soluble membrane attack complex (sMAC, a.k.a., sC5b-9 or TCC) is generated on activation of complement and contains the complement proteins C5b, C6, C7, C8, C9 together with the regulatory proteins clusterin and/or vitronectin. sMAC is a member of the MACPF/cholesterol-dependent-cytolysin superfamily of pore-forming molecules that insert into lipid bilayers and disrupt cellular integrity and function. sMAC is a unique complement activation macromolecule as it is comprised of several different subunits. To date no complement-mediated function has been identified for sMAC. sMAC is present in blood and other body fluids under homeostatic conditions and there is abundant evidence documenting changes in sMAC levels during infection, autoimmune disease and trauma. Despite decades of scientific interest in sMAC, the mechanisms regulating its formation in healthy individuals and its biological functions in both health and disease remain poorly understood. Here, we review the structural differences between sMAC and its membrane counterpart, MAC, and examine sMAC immunobiology with respect to its presence in body fluids in health and disease. Finally, we discuss the diagnostic potential of sMAC for diagnostic and prognostic applications and potential utility as a companion diagnostic.

Performance of clinical prediction rules for diagnosis of pleural tuberculosis in a high-incidence setting

OBJECTIVES

Diagnosis of pleural tuberculosis (PT) is still a challenge, particularly in resource-constrained settings. Alternative diagnostic tools are needed. We aimed at evaluating the utility of Clinical Prediction Rules (CPRs) for diagnosis of pleural tuberculosis in Peru.

METHODS

We identified CPRs for diagnosis of PT through a structured literature search. CPRs using high-complexity tests, as defined by the FDA, were excluded. We applied the identified CPRs to patients with pleural exudates attending two third-level hospitals in Lima, Peru, a setting with high incidence of tuberculosis. Besides pleural fluid analysis, patients underwent closed pleural biopsy for reaching a final diagnosis through combining microbiological and histopathological criteria. We evaluated the performance of the CPRs against this composite reference standard using classic indicators of diagnostic test validity.

RESULTS

We found 15 eligible CPRs, of which 12 could be validated. Most included ADA, age, lymphocyte proportion and protein in pleural fluid as predictive findings. A total of 259 patients were included for their validation, of which 176 (67%) had PT and 50 (19%) malignant pleural effusion. The overall accuracy of the CPRs varied from 41% to 86%. Two had a positive likelihood ratio (LR) above 10, but none a negative LR below 0.1. ADA alone at a cut-off of ≥40 IU attained 87% diagnostic accuracy and had a positive LR of 6.6 and a negative LR of 0.2.

CONCLUSION

Many CPRs for PT are available. In addition to ADA alone, none of them contributes significantly to diagnosis of PT.

Complement activation by Proteus mirabilis negatively charged lipopolysaccharides

Proteus mirabilis strains are human pathogens responsible for urinary tract infections and bacteremias and may be involved in rheumatoid arthritis. Lipopolysaccharide (LPS, bacterial endotoxin), the major component of the cell wall, is one of the virulence factors of Proteus. In the presented studies, we have investigated complement activation by LPSs isolated from P. mirabilis O10, O23, O30, and O43 strains, which differ in the number of negative COO— groups on their polysaccharide components. Four P. mirabilis strains studied were sensitive to complement-mediated killing, despite complement binding by their LPSs. The optimal complement binding by LPSs was detected in serum with functional assays for both the classical and alternative pathways.

Complement activation in 80% serum by the smooth, uronic acid, and hexosamine containing P. mirabilis LPSs was not critically determined by the structure of their O-chain polysaccharides. One of four LPSs used as a model, P. mirabilis O10 LPS, fragmented C3 in an LPS dose- and time-dependent manner. It was detected by crossed-immunoelectrophoresis and capture ELISA with anti-C3c antibodies. The lower complement activation by O23 LPS correlates with its reduced C3 fragmentation, compared with three other Proteus LPSs studied. Rabbit anti-O antibodies enhanced the complement binding and factor C3 fragmentation by O10, O23, O30, and O43 P. mirabilis LPSs.

COMP-C3b Complexes in Rheumatoid Arthritis with Severe Extraarticular Manifestations

Objective.

To investigate biomarker patterns in rheumatoid arthritis (RA) with extraarticular manifestations.

Methods.

Cartilage oligomeric matrix protein (COMP), COMP-C3b, and soluble terminal complement complexes (sTCC) were measured by ELISA.

Results.

COMP-C3b levels were higher in patients with RA than in healthy controls and lower in extraarticular RA (ExRA) than in RA controls. In patients with ExRA, sTCC levels were higher than in RA controls, and correlated inversely with serum COMP-C3b levels in the ExRA group.

Conclusion.

Patients with ExRA had lower levels of COMP-C3b. This may be a consequence of complement consumption or a lower potential for COMP from these patients to activate complement.

Pleural fluid analysis: standstill or a work in progress?

Pleural fluid analysis yields important diagnostic information in pleural effusions in combination with clinical history, examination, and radiology. For more than 30 years, the initial and most pragmatic step in this process is to determine whether the fluid is a transudate or an exudate. Light's criteria remain the most robust in separating the transudate-exudate classification which dictates further investigations or management. Recent studies have led to the evaluation and implementation of a number of additional fluid analyses that may improve the diagnostic utility of this method. This paper discusses the current practice and future direction of pleural fluid analysis in determining the aetiology of a pleural effusion. While this has been performed for a few decades, a number of other pleural characteristics are becoming available suggesting that this diagnostic tool is indeed a work in progress.

The lung in rheumatoid arthritis

Rheumatoid arthritis (RA) is a common inflammatory disease, affecting about 1% of the population. Although a major portion of the disease burden including excess mortality is due to its extra-articular manifestations, the prevalence of RA-associated lung disease is increasing. RA can affect the lung parenchyma, airways, and the pleura; and pulmonary complications are directly responsible for 10 to 20% of all mortality. Even though pulmonary infection and drug toxicity are frequent complications of RA, lung disease directly associated with the underlying RA is more common. The prevalence of a particular complication varies based on the characteristics of the population studied, the definition of lung disease used, and the sensitivity of the clinical investigations employed. An overview of lung disease associated with RA is presented here with an emphasis on parenchymal lung disease, pleural effusion, and airway involvement.

The use of non-routine pleural fluid analysis in the diagnosis of pleural effusion

The investigation of a pleural effusion is, in general, a very straight forward process with the combination of clinical history, examination, radiology and pleural fluid analysis leading to diagnosis in most cases. While most fluid samples are sent for routine analysis including protein, LDH, glucose, cytology and microbiology, there are a number of more unusual fluid analyses available which in some cases directly lead to, and in others are suggestive of the diagnosis. Moreover, other fluid markers are constantly being evaluated as a diagnostic tool. In this review, we describe these non-routine pleural fluid analyses in detail. English language publications in MEDLINE and references from relevant articles from January 1 1990 to August 1 2009 were reviewed. Keywords searched in combination were pleural fluid, effusion, analysis, transudate, exudate and diagnosis.

Proteomic analysis of pericardial effusion: Characteristics of tuberculosis-related proteins

The aim of this study has been designed to identify the tuberculosis (TB)-related proteins in pericardial effusion by proteomic approaches. TB is one of the major infectious diseases causing pericardial effusion. This study details protein profiles in pericardial effusion from three TB patients and three heart failure patients. Pericardial effusions were analyzed using 2-DE combined with the nano-HPLC-ESI-MS/MS. Eleven protein spots with differential expression in pericardial effusion were identified between the two groups of TB and heart failure patients (the control group). Seven protein spots were upregulated and four were downregulated. The composition of the pericardial effusion proteome may reflect the pathophysiological conditions affecting the progression of tuberculous pericarditis. The proteins in the tuberculous pericardial effusion with differential expression may serve as new and direct indicators of drug treatment. A possible conclusion is indicated that fibrinogen may play an important role for fibrin assembly in tuberculous pericardial effusion.

Rheumatoid Pleural Effusion

OBJECTIVES

To describe the clinical and laboratory features of rheumatoid pleural effusion (RPE) and the diagnostic and therapeutic approaches to this condition.

METHODS

The review is based on a MEDLINE (PubMed) search of the English literature from 1964 to 2005, using the keywords "rheumatoid arthritis" (RA), "pulmonary complication", "pleural effusion", and "empyema".

RESULTS

Pleural effusion is common in middle-aged men with RA and positive rheumatoid factor (RF). It has features of an exudate and a high RF titer. Underlying lung pathology is common. Generally RPE is small and resolves spontaneously but symptomatic RPE may require thoracocentesis. Rarely, RPE has features of a sterile empyematous exudate with high lipids and lactate dehydrogenase, and very low glucose and pH levels. This type of effusion eventually leads to fibrothorax and lung restriction. Superimposed infective empyema often complicates RPE. Oral, parenteral, and intrapleural corticosteroids, pleurodesis and decortication, have been used for the treatment of sterile RPE. Infected empyema is treated with drainage and antibiotics.

CONCLUSIONS

RPE may evolve into a sterile empyematous exudate with the development of fibrothorax. Symptomatic effusions or suspicion of other causes of exudate (infection, malignancy) require thoracocentesis. The "rheumatoid" nature of the pleural exudate in patients without arthritis mandates a pleural biopsy to exclude tuberculosis or malignancy. The optimal therapy of RPE has yet to be established. The role of cytokines in the course of RPE and the possible usefulness of cytokine blockade in the treatment of this RA complication require further evaluation.

Serositis related to systemic lupus erythematosus: prevalence and outcome

The objective of this study was to describe the prevalence and outcome of disease-related serositis in Chinese patients with systemic lupus erythematosus (SLE). The records of all SLE patients who attended the medical clinics of Tuen Mun Hospital, Hong Kong were retrospectively reviewed. Patients with disease-related serositis at any stage of their illness were identified and the outcome of these serositis episodes was reported. Three-hundred and ten patients (90% women) who fulfilled at least four of the ACR criteria for SLE were studied. The mean age of SLE onset was 32.6 +/- 13.1 years. sixty-nine episodes of SLE-related serositis occurred in 37 patients - 18 (26%) episodes were pericarditis/ pericardial effusion, 30 (44%) were pleuritis/pleural effusion and 21 (30%) were peritonitis/ascites. The prevalence of serositis was 12%. At the time of serositis, 34 (92%) patients had active SLE in other systems. Nonsteroidal anti-inflammatory drugs (NSAIDs) were initially used in 13 (35%) patients. Moderate to high doses of oral prednisolone was used in 28 (76%) patients for both serositis and concomitant disease activity in other organs. All episodes of serositis resolved completely within two months. Over a mean observation of 46 months, nine patients had 18 relapses of serositis, which were responsive to either NSAIDs or augmentation of prednisolone dosage. Pleural fibrosis developed in three patients. Serosal complications are not uncommon in patients with SLE and can be life-threatening. NSAIDs and corticosteroids are often effective but more aggressive immunosuppressive therapy is required for severe or refractory cases. The prognosis of lupus serositis is generally good. Relapse or progression to fibrotic disease is uncommon.

Assaying of tumor necrosis factor alpha, complement factors, and alpha-1-antitrypsin in the diagnosis of malignant serous effusions

The objective of this study was to measure the concentrations of tumor necrosis factor-alpha (TNFalpha) in pleural and peritoneal effusions of different causes and to verify whether TNFalpha, alpha-1-antitrypsin (alpha1AT), and complement factors C3 and C4 can be used in the differential diagnosis of serous effusion. One hundred forty-five serous effusions of various origins were analyzed. TNFalpha, alpha1AT, and complement factors C3 and C4 concentrations were measured simultaneously in blood and serous effusion using commercially available methods. Serous effusions were classified as follows: 102 exudates and 43 transudates. All variables were found to have good diagnostic value in the differential diagnosis of serous effusion. In the stepwise discriminant analysis, four variables were selected, producing a significant discriminant function (p < 0.001). Their order of selection was alpha1AT effusion, C4 serum, TNFalpha-effusion, and C3 effusion. Combined use of these variables increased remarkably the diagnostic value (in diagnosing exudates versus transudates) giving sensitivity = 93.14%; specificity = 90.70%; positive predictive value = 95.96%; negative predictive value = 84.78%. Determination of TNFalpha, complement factors C3 and C4, and alpha1AT may be a significant parameter in the differential diagnosis of serous effusions, particularly in those patients with malignant disease. Moreover, the combination of them significantly increased their diagnostic power.