Anti-C1q autoantibodies in lupus nephritis

Urticarial Vasculitis

Urticarial vasculitis is a rare autoimmune disorder characterized by persistent edematous papules and plaques on the skin that last longer than 24 hours, often accompanied by systemic symptoms such as joint pain and fever. Unlike common urticaria, this condition involves inflammation of small blood vessels, leading to more severe and long-lasting skin lesions with a tendency to leave a bruiselike appearance. Diagnosis is challenging and may require a skin biopsy. Associated with underlying autoimmune diseases, treatment involves managing symptoms with medications such as antihistamines and corticosteroids, addressing the immune system's dysfunction, and treating any concurrent autoimmune conditions.

Anti-C1q antibodies: a biomarker for diagnosis and management of lupus nephritis. A narrative review

Nephritis is a frequent and severe complication of Systemic Lupus Erythematous (SLE). The clinical course of lupus nephritis (LN) is usually characterized by alternating phases of remission and exacerbation. Flares of LN can lead to deterioration of kidney function, necessitating timely diagnosis and therapy. The presence of autoantibodies against C1q (anti-C1qAb) in the sera of SLE patients has been reported in various studies. Some research suggests that the presence and changes in the titer of anti-C1qAb may be associated with the development of LN, as well as with LN activity and renal flares. However, the exact role of anti-C1qAb in LN remains a subject of debate. Despite variability in the results of published studies, anti-C1qAb hold promise as noninvasive markers for assessing LN activity in SLE patients. Measuring anti-C1qAb levels could aid in diagnosing and managing LN during periods of both inactive disease and renal flares. Nevertheless, larger controlled trials with standardized laboratory assays are necessary to further establish the utility of anti-C1qAb in predicting the reactivation and remission of LN and guiding treatment strategies.

The role of online hemodiafiltration with endogenous reinfusion in the treatment of systemic lupus erythematosus activity resistant to conventional therapy

Introduction

Lupus is a diverse autoimmune disease with autoantibody formation. Lupus nephritis carries a grave prognosis. Complement involvement, namely, C1q deficiency, is linked to activity and renal involvement and could help in their assessment. LN therapies include plasma exchange, immune adsorption, and probably hemodiafiltration with online endogenous reinfusion (HFR), together with traditional immunosuppressive therapies.

Aim

The aim of this study was to evaluate the role of HFR in improving signs and symptoms of systemic lupus erythematosus (SLE) activity and laboratory parameters in cases not responding to traditional immunosuppressive therapy.

Settings and design

A controlled clinical study was conducted on 60 patients with lupus from Group A that was subdivided into two groups: cases 1 (47 patients), those who received traditional medical treatment, and cases 2 (13 patients), those who underwent HFR in addition to medical treatment. Group B consisted of two subgroups: control 1, composed of 20 healthy age- and sex-matched volunteers, and control 2, consisting of 10 cases with different glomerular diseases other than lupus.

Methods and materials

Serum C1q was determined before and after the HFR as well as induction by medical treatment. Disease activity was assessed using SLEDAI-2K with a responder index of 50; quality of life was assessed using SLEQOL v2, and HFR was performed for the non-responder group.

Results

C1q was lower in cases. It can efficiently differentiate between SLE patients and healthy controls with a sensitivity of 81.67% and a specificity of 90%. It can also efficiently differentiate between SLE patients and the control 2 group (non-lupus patients with renal glomerular disease) with a sensitivity of 83.33% and a specificity of 100%. C1q was more consumed in proliferative lupus, and correlated with anti-ds DNA, C3, and C4.

Conclusions

C1q efficiently discriminates lupus patients and correlates with proliferative forms. HFR might ameliorate lupus activity and restore C1q.

Association of urine autoantibodies with disease activity in systemic lupus erythematosus

Objective

The presence of urinary autoantibodies in patients with systemic lupus erythematosus (SLE) has been confirmed by several studies; however, the significance of their presence in urine remains unclear. This study aims to further investigate the association between urine autoantibodies and disease activity as well as organ involvement in SLE.

Methods

This cross-sectional study included 89 SLE patients. Data collected included anti-nuclear antibody (ANA), anti-ENA antibodies, and anti-dsDNA antibody levels in both serum and urine, complement (C) 3, C4 levels in serum, SLE disease activity index-2000 (SLEDAI-2000), renal domains of SLEDAI (RSLEDAI) and non-renal SLEDAI (NRSLEDAI).

Results

The rate of positive urine ANA (uANA) was 33.3% (29/87) among the enrolled patients. Compared to the uANA negative group, the positive group exhibited significantly higher SLEDAI-2000 scores (7.85 ± 5.88 vs. 18.69 ± 6.93, p < 0.001), RSLEDAI scores [0 (0, 4.0) vs. 12.0 (8.0, 16.0), p < 0.001], and NRSLEDAI [4 (2.0, 8.0) vs. 6.0 (4.0, 9.5), p = 0.038]. Patients with positive urine anti-Sm antibody demonstrated significantly elevated SLEDAI-2000 scores compared to those who were negative (25.0 ± 8.80 vs. 10.09 ± 6.63, p < 0.001). Similarly, they also had higher RSLEDAI [16.0 (12.0, 16.0) vs. 4.0 (0, 8.0), p < 0.001] and NRSLEDAI [9.5 (6.0, 13.5) vs. 4.0 (3.0, 8.0), p = 0.012], as well as a greater prevalence of renal involvement compared to their negative counterparts (100% vs. 58.2, p = 0.022). There was a positive correlation between uANA titer and both SLEDAI-2000 (rs = 0.663, p < 0.001) and RSLEDAI (rs = 0.662, p < 0.001). The serum anti-dsDNA antibody level did not exhibit a significant correlation with RSLEDAI (rs = 0.143, p = 0.182). Conversely, the urine anti-dsDNA antibody level demonstrated a significant positive correlation with RSLEDAI (rs = 0.529, p < 0.001).

Conclusion

Urine ANA is associated with both global SLEDAI and RSLEDAI scores. Urine anti-Sm antibody is associated with an increased incidence of renal involvement in SLE. The urine anti-dsDNA antibody level, rather than the serum anti-dsDNA antibody level, exhibits a significant association with RSLEDAI in SLE.

Consensus document of the Spanish Group for the Study of the Glomerular Diseases (GLOSEN) for the diagnosis and treatment of lupus nephritis

A significant number of patients with systemic lupus erythematosus (between 20% and 60% according to different reported series) develop lupus nephritis in the course of its evolution, which directly influences their quality of life and vital prognosis. In recent years, the greater knowledge about the pathogenesis of systemic lupus and lupus nephritis has allowed relevant advances in the diagnostic approach and treatment of these patients, achieving the development of drugs specifically aimed at blocking key pathogenic pathways of the disease. Encouragingly, these immunomodulatory agents have shown in well-powered, randomized clinical trials good clinical efficacy in the medium-term, defined as proteinuria remission and preservation of kidney function, with an acceptable safety profile and good patient tolerability. All this has made it possible to reduce the use of corticosteroids and other potentially more toxic therapies, as well as to increase the use of combined therapies. The present consensus document carried out by the Glomerular Diseases Working Group of the Spanish Society of Nephrology (GLOSEN), collects in a practical and summarized, but rigorous way, the best currently available evidence about the diagnosis, treatment, and follow-up of lupus nephritis patients, including cases of special situations, with the main objective of providing updated information and well-founded clinical recommendations to treating physicians, to improve the diagnostic and therapeutic approach to our patients.

Correct approach in urticarial vasculitis made early diagnosis of lupus nephritis possible: a case report

Background

Urticarial vasculitis is a clinicopathologic entity defined by recurrent episodes of urticarial lesions that persist > 24 hours and demonstrate the histopathologic features of leukocytoclastic vasculitis. The most important prognostic feature is the presence of normo- or hypocomplementemia. In the latter, patients are much more likely to have systemic manifestations. Urticarial vasculitis is most often idiopathic, but it can arise in association with autoimmune connective diseases, cryoglobulinemia, infections, medications, and hematologic malignancies.

Case presentation

We present the case of a 61-year-old Caucasian woman with a skin eruption that consisted of erythematous plaques on the trunk and limbs that lasted > 24 hours but were asymptomatic. The skin eruption had an acute onset and persisted for 3 months upon initial presentation in our dermatology department. A punch biopsy showed signs of a leukocytoclastic vasculitis in the superficial dermis. On laboratory examination, signs of activation of the complement system were found with low complement C3, C4, and C1q, and with a high anti-C1q antibody titer. The clinical, histological, and lab results fit the diagnosis of hypocomplementemic urticarial vasculitis. There was also a positive antinuclear factor with elevated U1 small nuclear ribonucleoprotein and high double-stranded DNA determined by Farr method. On urinalysis, marked proteinuria and massive hematuria were found. Kidney biopsy showed focal crescentic and focal mesangial type of glomerular damage with a full-blown positivity of immunoglobulin A, immunoglobulin G, and C1q, leading to lupus nephritis class III-A (according to the International Society of Nephrology/Renal Pathology Society 2003 classification of lupus nephritis). The patient was treated with hydroxychloroquine, corticosteroids, and low-dose intravenous cyclophosphamide (Euro-Lupus regimen) as remission-inducing agent, followed by azathioprine as remission-maintaining agent. This treatment regimen gave good results, with total clearance of the skin lesions and remission of the lupus nephritis.

Conclusion

Clinicopathologic recognition of urticarial vasculitis with correct screening for extracutaneous disease can lead to early diagnosis of serious organ involvement and thereby improve prognosis for the patient.

Intertwined pathways of complement activation command the pathogenesis of lupus nephritis

The complement system is involved in the origin of autoimmunity and systemic lupus erythematosus. Both genetic deficiency of complement components and excessive activation are involved in primary and secondary renal diseases, including lupus nephritis. Among the pathways, the classical pathway has long been accepted as the main pathway of complement activation in systemic lupus erythematosus. However, more recent studies have shown the contribution of factors B and D which implies the involvement of the alternative pathway. While there is evidence on the role of the lectin pathway in systemic lupus erythematosus, it is yet to be demonstrated whether this pathway is protective or harmful in lupus nephritis. Complement is being explored for the development of disease biomarkers and therapeutic targeting. In the current review we discuss the involvement of complement in lupus nephritis.

The roles of basophils in mediating the immune responses

Basophils are the rarest blood cell population and have not been extensively studied. Our understanding of the functions of basophils is limited to their roles as the main effector cells in hypersensitivity reactions. Similar to mast cells, basophils express high-affinity IgE receptor (FcεRI), contain granules, and release hypersensitivity-associated mediators (such as histamine). The roles of basophils have not been fully elucidated; however, with the rapid development of monoclonal techniques, high-purity cell sorting techniques, and basophil-deficient mouse models, understanding of the functions and phenotypes of basophils has increased. This facilitates further investigations on the relationships between basophils and host immunity. Basophils are not only involved in mediating the generation of allergic reactions but also play important roles in immunomodulation and are responsible for the onset of infectious, allergic, and autoimmune diseases. In this review, we summarize the progress in understanding the roles of basophils in mediating immune responses with an emphasis on autoimmune diseases, particularly systemic lupus erythematosus and rheumatoid arthritis.

Serum IgG2 antibody multicomposition in systemic lupus erythematosus and lupus nephritis (Part 1): cross-sectional analysis

OBJECTIVES

Serum anti-dsDNA and anti-nucleosome IgGs have been proposed as signatures for SLE and LN in limited numbers of patients. We sought to show higher sensitivity and specificity of the same antibodies with the IgG2 isotype and included IgG2 antibodies vs specific intracellular antigens in the analysis.

METHODS

A total of 1052 SLE patients with (n = 479) and without (n = 573) LN, recruited at different times from the beginning of symptoms, were included in the study. Patients with primary APS (PAPS, n = 24), RA (RA, n = 24) and UCTD (UCTD, n = 96) were analysed for comparison. Anti-nucleosome (dsDNA, Histone2A, Histone3), anti-intracellular antigens (ENO1), anti-annexin A1 and anti-C1q IgG2 were determined by non-commercial techniques.

RESULTS

The presence in the serum of the IgG2 panel was highly discriminatory for SLE/LN vs healthy subjects. Serum levels of anti-dsDNA and anti-C1q IgG2 were more sensitive than those of IgGs (Farr radioimmunoassay/commercial assays) in identifying SLE patients at low-medium increments. Of more importance, serum positivity for anti-ENO1 and anti-H2A IgG2 discriminated between LN and SLE (ROC T0-12 months), and high levels at T0-1 month were detected in 63% and 67%, respectively, of LN, vs 3% and 3%, respectively, of SLE patients; serum positivity for each of these was correlated with high SLEDAI values. Minor differences existed between LN/SLE and the other rheumatologic conditions.

CONCLUSION

Nephritogenic IgG2 antibodies represent a specific signature of SLE/LN, with a few overlaps with other rheumatologic conditions. High levels of anti-ENO1 and anti-H2A IgG2 correlated with SLE activity indexes and were discriminatory between SLE patients limited to the renal complication and other SLE patients.

TRIAL REGISTRATION

The Zeus study was registered at https://clinicaltrials.gov, NCT02403115.

Serum IgG2 antibody multi-composition in systemic lupus erythematosus and in lupus nephritis (Part 2): prospective study

OBJECTIVES

Circulating anti-ENO1 and anti-H2A IgG2 have been identified as specific signatures of LN in a cross-over approach. We sought to show whether the same antibodies identify selected population of patients with LN with potentially different clinical outcomes.

METHODS

Here we report the prospective analysis over 36 months of circulating IgG2 levels in patients with newly diagnosed LN (n=91) and SLE (n=31) and in other patients with SLE recruited within 2 years from diagnosis (n=99). Anti-podocyte (ENO1), anti-nucleosome (DNA, histone 2 A, histone 3) and anti-circulating proteins (C1q, AnnexinA1-ANXA1) IgG2 antibodies were determined by home-made techniques.

RESULTS

LN patients were the main focus of the study. Anti-ENO1, anti-H2A and anti-ANXA1 IgG2 decreased in parallel to proteinuria and normalized within 12 months in the majority of patients while anti-dsDNA IgG2 remained high over the 36 months. Anti-ENO1 and anti-H2A had the highest association with proteinuria (Heat Map) and identified the highest number of patients with high proteinuria (68% and 71% respectively) and/or with reduced estimated glomerula filtration rate (eGFR) (58% for both antibodies) compared with 23% and 17% of anti-dsDNA (agreement analysis). Anti-ENO1 positive LN patients had higher proteinuria than negative patients at T0 and presented the maximal decrement within 12 months.

CONCLUSIONS

Anti-ENO1, anti-H2A and anti-ANXA1 antibodies were associated with high proteinuria in LN patients and Anti-ENO1 also presented the maximal reduction within 12 months that paralleled the decrease of proteinuria. Anti-dsDNA were not associated with renal outcome parameters. New IgG2 antibody signatures should be utilized as tracers of personalized therapies in LN.

TRIAL REGISTRATION

The Zeus study was registered at https://clinicaltrials.gov (study number: NCT02403115).

Clinical and Immunological Biomarkers for Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is characterized by immune system dysfunction and is clinically heterogeneous, exhibiting renal, dermatological, neuropsychiatric, and cardiovascular symptoms. Clinical and physiological assessment is usually inadequate for diagnosing and assessing pathophysiological processes in SLE. Clinical and immunological biomarkers could play a critical role in improving diagnosis, assessment, and ultimately, control of SLE. This article reviews clinical and immunological biomarkers that could diagnose and monitor disease activity in SLE, with and without organ-specific injury. In addition, novel SLE biomarkers that have been discovered through “omics” research are also reviewed.

High frequency of concurrent anti-C1q and anti-dsDNA but not anti-C3b antibodies in patients with Lupus Nephritis

Lupus Nephritis (LN) in patients with Systemic Lupus Erythematosus (SLE) is one of the most serious and prevalent manifestations. The procedure of renal biopsy is harmful and accompanied by potential hazards. Therefore, introducing reliable biomarkers to predict LN is exceedingly worthwhile. In the present study, we compared the diagnostic values of circulating autoantibodies against dsDNA, C1q, C3b, SSA, SSB, and Sm alone or in combination to predict LN. This study evaluated the abovementioned autoantibodies in 40 healthy controls (HCs) and 95 SLE patients with different kidney involvements, including absent (n = 40), inactive (n = 20), and active (n = 35) LN using EIA method. The frequency and odds ratio of anti-dsDNA (71.4%, OR = 4.2), anti-C1q (62.9%, OR = 5.1), and the simultaneous existence of anti-C1q and anti-dsDNA (51.4%, OR = 6) antibodies were significantly higher in the active LN group compared with both inactive and absent LN groups. Moreover, the levels of anti-C1q and anti-dsDNA antibodies positively correlated with disease activity in patients with SLE. The prevalence of these autoantibodies was associated with the severity of LN biopsies. These data suggest that anti-C1q and anti-dsDNA antibodies and also their simultaneous presence may be valuable diagnostic biomarkers for LN prediction in patients with SLE.

Expanding the Role of Complement Therapies: The Case for Lupus Nephritis

The complement system is an innate immune surveillance network that provides defense against microorganisms and clearance of immune complexes and cellular debris and bridges innate and adaptive immunity. In the context of autoimmune disease, activation and dysregulation of complement can lead to uncontrolled inflammation and organ damage, especially to the kidney. Systemic lupus erythematosus (SLE) is characterized by loss of tolerance, autoantibody production, and immune complex deposition in tissues including the kidney, with inflammatory consequences. Effective clearance of immune complexes and cellular waste by early complement components protects against the development of lupus nephritis, while uncontrolled activation of complement, especially the alternative pathway, promotes kidney damage in SLE. Therefore, complement plays a dual role in the pathogenesis of lupus nephritis. Improved understanding of the contribution of the various complement pathways to the development of kidney disease in SLE has created an opportunity to target the complement system with novel therapies to improve outcomes in lupus nephritis. In this review, we explore the interactions between complement and the kidney in SLE and their implications for the treatment of lupus nephritis.

Systemic lupus erythematosus: The search for the ideal biomarker

During the last decades, there has been an increased interest in the discovery and validation of biomarkers that reliably reflect specific aspects of lupus. Although many biomarkers have been developed, few of them have been validated and used in clinical practice, but with unsatisfactory performances. Thus, there is still a need to rigorously validate many of these novel promising biomarkers in large-scale longitudinal studies and also identify better biomarkers not only for lupus diagnosis but also for monitoring and predicting upcoming flares and response to treatment. Besides serological biomarkers, urinary and cerebrospinal fluid biomarkers have emerged for assessing both renal and central nervous system involvement in systemic lupus erythematosus, respectively. Also, novel omics techniques help us to understand the molecular basis of the disease and also allow the identification of novel biomarkers which may be potentially useful for guiding new therapeutic targets.

An Update on Antibodies to Necleosome Components as Biomarkers of Sistemic Lupus Erythematosus and of Lupus Flares

Systemic lupus erythematosus (SLE) is an autoimmune disease with variable clinical expression. It is a potentially devastating condition affecting mostly women and leading to clinically unpredictable outcomes. Remission and flares may, in fact, alternate over time and a mild involvement limited to few articular sites may be followed by severe and widespread organ damage. SLE is the prototype of any autoimmune condition and has, for this reason, attracted the interest of basic immunologists. Therapies have evolved over time and clinical prognosis has, in parallel, been improved. What clinicians still lack is the possibility to use biomarkers of the disease as predictors of outcome and, in this area, several studies are trying to find solutions. Circulating autoantibodies are clearly a milestone of clinical research and the concrete possibility is to integrate, in the future, classical markers of activation (like C3) with target organ autoantibodies. Anti-dsDNA antibodies represent a basic point in any predictive attempt in SLE and should be considered the benchmark for any innovative proposal in the wide field of target organ pathologies related to SLE. DNA is part of the nucleosome that is the basic unit of chromatin. It consists of DNA wrapped around a histone octamer made of 2 copies each of Histone 2A, 2B, 3, and 4. The nucleosome has a plastic organization that varies over time and has the potential to stimulate the formation of antibodies directed to the whole structure (anti-nucleosome) or its parts (anti-dsDNA and anti-Histones). Here, we present an updated review of the literature on antibodies directed to the nucleosome and the nucleosome constituents, i.e., DNA and Histones. Wetriedto merge the data first published more than twenty years ago with more recent results to create a balanced bridge between old dogma and more recent research that could serve as a stimulus to reconsider mechanisms for SLE. The formation of large networks would provide the chance of studying large cohorts of patients and confirm what already presented in small sample size during the last years.

A new look at IgE beyond allergies

Immunoglobulin E (IgE), though constitutively present at low levels, is most commonly studied in atopic disease where it plays a vital role in mast cell degranulation and in initiating a T helper 2 (Th2) response. With the advent of better detection assays, however, researchers are discovering the importance of IgE in actively contributing to many disease states and pathologies. This review will discuss the latest findings in IgE beyond its role in allergies and recently discovered roles for IgE in its cell-bound form on FcεRI-expressing effector cells like monocytes and dendritic cells. In terms of parasites, we will discuss helminth-induced IgE that appears to protect the worms from immune recognition and a tick-borne illness that elicits an IgE response against red meat. Next, we describe recent findings of how auto-reactive IgE can contribute to the progression of lupus and induce organ damage. Finally, we summarize the emerging roles of IgE in tumor surveillance and antibody-dependent cytotoxicity. We additionally discuss recent or ongoing clinical trials that either target harmful IgE or use the unique characteristics of the isotype.

Antibodies targeting circulating protective molecules in lupus nephritis: Interest as serological biomarkers

Lupus nephritis (LN) is one of the most frequent and severe manifestations of systemic lupus erythematosus (SLE), considered as the major predictor of poor prognosis. An early diagnosis of LN is a real challenge in the management of SLE and has an important implication in guiding treatments. In clinical practice, conventional parameters still lack sensitivity and specificity for detecting ongoing disease activity in lupus kidneys and early relapse of nephritis. LN is characterized by glomerular kidney injury, essentially due to deposition of immune complexes involving autoantibodies against cellular components and circulating proteins. One of the possible mechanisms of induction of autoantibodies in SLE is a defect in apoptotic cells clearance and subsequent release of intracellular autoantigens. Autoantibodies against soluble protective molecules involved in the uptake of dying cells, including complement proteins and pentraxins, have been described. In this review, we present the main autoantibodies found in LN, with a focus on the antibodies against these protective molecules. We also discuss their pathogenic role and conclude with their potential interest as serological biomarkers in LN.

Anti-C1q autoantibodies as markers of renal involvement in childhood-onset systemic lupus erythematosus

BACKGROUND

Childhood-onset systemic lupus erythematosus (cSLE) is rare, and considered more severe than its adult-onset counterpart. Lupus nephritis (LN) occurs more frequently in children, accounting for higher long-term morbidity and mortality compared with adults. Thus, reliable biological markers are needed to predict disease course. This study aimed to investigate the capacity of anti-C1q autoantibodies (Abs) to predict renal flare and global disease activity in cSLE patients, and association with disease activity and kidney involvement.

METHODS

Twenty-eight patients with cSLE including 19 patients (68%) with a history of LN were included retrospectively. Anti-C1q Abs were analysed by ELISA at renal flare-up or in the quiescent phase of disease and compared with Farr dsDNA assay.

RESULTS

Thirty-one flares occurred during follow-up: anti-C1q Abs were positive in 26 (84%), strongly associated with active disease status (p < 0.0001), and correlated with global disease activity score (p < 0.0001) and anti-dsDNA Abs presence (p < 0.0001). The specificity of anti-C1q Abs was higher than anti-dsDNA (73% vs 19%) in discriminating LN patients, whereas the receiver operating characteristic curves were not statistically different (0.83 ± 0.06 vs 0.78 ± 0.08 respectively), similar to C3 dosage. The presence of anti-C1q Abs at diagnosis was not predictive for global or renal flare. Introduction of a modified SLEDAI score excluding dsDNA Abs, demonstrated a stronger correlation of anti-C1q Abs titres with SLEDAI score in comparison with the Farr test.

CONCLUSION

Anti-C1q Abs seem very specific to flares, including LN in children, and their role in daily practice compared with the Farr dsDNA assay needs to be defined.

MMP2 and MMP9 associate with crescentic glomerulonephritis

Background: Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by multiple organ involvement. Lupus nephritis (LN) is a common manifestation with a wide variety of histological appearances. Matrix metalloproteinases (MMP) 2 and 9 are gelatinases capable of degrading glomerular basement membrane type IV collagen, which have been associated with LN. We examine the expression of MMP2 and MMP9 in different classes of LN.

Methods: MMP2 and MMP9 expression was detected by immunohistochemistry in sections from renal biopsy specimens with class III, class IV and class V LN (total n = 31), crescentic immunoglobulin A nephropathy (n = 6), pauci-immune glomerulonephritis (n = 7), minimal change disease (n = 2), mesangiocapillary glomerulonephritis (n = 7), diabetic nephropathy (n = 12) and histologically normal controls (n = 8).

Results: MMP2 and MMP9 were not expressed in all classes of LN, but were observed in LN with cellular and fibrocellular crescents. MMP2/MMP9 was expressed in cellular and fibrocellular crescents regardless of glomerulonephritis but not observed in inactive fibrous crescents or with mesangial proliferation. This suggests that MMP2 and MMP9 are involved in the development of extracapillary proliferative lesions.

Conclusions: MMP2/MMP9 is expressed with active extracapillary proliferation. Further study is necessary to define whether the expression of MMP2/MMP9 reflects a role in glomerular repair after injury, a role in organ-level immune responses or a role as a marker of epithelialization.

PTX3, Anti-PTX3, and Anti-C1q Autoantibodies in Lupus Glomerulonephritis

Pentraxin 3 (PTX3) is an acute-phase protein involved in C1q clearance. The presence of anti-C1q and the absence of anti-PTX3 antibodies were associated with lupus glomerulonephritis (LGLN). Our aim was to assess soluble and kidney-expressed PTX3 and their relationships with anti-C1q and anti-PTX3 antibodies in LGLN. Serum PTX3, anti-C1q, anti-dsDNA, and anti-PTX3 antibodies were tested in 130 systemic lupus erythematosus (SLE) patients, 130 healthy and 127 disease controls. Twenty-nine renal biopsies from SLE patients were analyzed and PTX3 immunostaining was quantified by morphometric analysis. Parametric and nonparametric statistics were performed. PTX3 serum levels were lower in SLE versus controls, but they were correlated with proteinuria in LGLN patients (p = 0.001). LGLN patients had higher anti-C1q and lower anti-PTX3 antibody levels than those without (p < 0.0001). LGLN was more prevalent in anti-C1q(+)/anti-PTX3(-) than in anti-C1q(+)/anti-PTX3(+) patients (p < 0.001). No LGLN was observed in anti-C1q(-)/anti-PTX3(+) patients. PTX3 was expressed in glomeruli and renal interstitium. Renal PTX3 was correlated with proteinuria (p = 0.024) and interstitial fibrosis (p = 0.023). PTX3 staining and fibrosis were higher in anti-PTX3(-) than anti-PTX3(+) patients. In conclusion, PTX3 is expressed in glomeruli of LGLN patients, primarily in anti-PTX3(-) patients, where it is correlated with renal fibrosis. Anti-C1q/anti-PTX3 antibody profile seems to be useful in LGLN assessment.

Systemic Lupus Erythematosus and Deficiencies of Early Components of the Complement Classical Pathway

The complement system plays an important role in the innate and acquired immune response against pathogens. It consists of more than 30 proteins found in soluble form or attached to cell membranes. Most complement proteins circulate in inactive forms and can be sequentially activated by the classical, alternative, or lectin pathways. Biological functions, such as opsonization, removal of apoptotic cells, adjuvant function, activation of B lymphocytes, degranulation of mast cells and basophils, and solubilization and clearance of immune complex and cell lysis, are dependent on complement activation. Although the activation of the complement system is important to avoid infections, it also can contribute to the inflammatory response triggered by immune complex deposition in tissues in autoimmune diseases. Paradoxically, the deficiency of early complement proteins from the classical pathway (CP) is strongly associated with development of systemic lupus erythematous (SLE) - mainly C1q deficiency (93%) and C4 deficiency (75%). The aim of this review is to focus on the deficiencies of early components of the CP (C1q, C1r, C1s, C4, and C2) proteins in SLE patients.

Clearance Deficiency and Cell Death Pathways: A Model for the Pathogenesis of SLE

Alterations of cell death pathways, including apoptosis and the neutrophil specific kind of death called NETosis, can represent a potential source of autoantigens. Defects in the clearance of apoptotic cells may be responsible for the initiation of systemic autoimmunity in several chronic inflammatory diseases, including systemic lupus erythematosus (SLE). Autoantigens are released mainly from secondary necrotic cells because of a defective clearance of apoptotic cells or an inefficient degradation of DNA-containing neutrophil extracellular traps (NETs). These modified autoantigens are presented by follicular dendritic cells to autoreactive B cells in germinal centers of secondary lymphoid organs. This results in the loss of self-tolerance and production of autoantibodies, a unifying feature of SLE. Immune complexes (IC) are formed from autoantibodies bound to uncleared cellular debris in blood or tissues. Clearance of IC by blood phagocytes, macrophages, and dendritic cells leads to proinflammatory cytokine secretion. In particular, plasmacytoid dendritic cells produce high amounts of interferon-α upon IC uptake, thereby contributing to the interferon signature of patients with SLE. The clearance of antinuclear IC via Fc-gamma receptors is considered a central event in amplifying inflammatory immune responses in SLE. Along with this, the accumulation of cell remnants represents an initiating event of the etiology, while the subsequent generation of autoantibodies against nuclear antigens (including NETs) results in the perpetuation of inflammation and tissue damage in patients with SLE. Here, we discuss the implications of defective clearance of apoptotic cells and NETs in the development of clinical manifestations in SLE.

Relationship of Circulating Anti-C3b and Anti-C1q IgG to Lupus Nephritis and Its Flare

BACKGROUND AND OBJECTIVES

Autoantibodies to complement C1q (anti-C1q) are associated with the diagnosis of lupus nephritis. In this study, we compare anti-C1q IgG with another complement autoantibody, anti-C3b IgG, as a biomarker of lupus nephritis and lupus nephritis flare.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Our investigation involved the Ohio SLE Study, a prospective observational cohort of patients with recurrently active lupus who were followed bimonthly. Serum anti-C1q and anti-C3b IgG levels were assessed cross-sectionally by ELISA in 40 normal controls and 114 patients in the Ohio SLE Study (41 nonrenal and 73 lupus nephritis) at study entry, and longitudinally in a subset of patients in the Ohio SLE Study with anti-C1q-positive lupus nephritis in samples collected every 2 months for 8 months leading up to lupus nephritis flare (n=16 patients).

RESULTS

In the cross-sectional analysis, compared with anti-C1q IgG, anti-C3b IgG was less sensitive (36% versus 63%) but more specific (98% versus 71%) for lupus nephritis. Only anti-C3b IgG was associated with patients with lupus nephritis who experienced at least one lupus nephritis flare during the Ohio SLE Study period (P<0.01). In the longitudinal analysis, circulating levels of anti-C1q IgG increased at the time of lupus nephritis flare only in patients who were anti-C3b positive (P=0.02), with significant increases occurring from 6 (38% increase) and 4 months (41% increase) before flare. Anti-C3b IgG levels also trended up at lupus nephritis flare, although the change did not reach statistical significance (P=0.07). Neither autoantibody increased 2 months before flare.

CONCLUSIONS

Although not as prevalent as anti-C1q IgG, anti-C3b IgG showed nearly complete specificity for lupus nephritis. The presence of anti-C3b IgG identified patients with lupus nephritis who were prone to flare and in whom serial measurements of markers associated with complement, such as anti-C1q IgG, may be useful to monitor lupus nephritis activity.

Antibodies against C1q Are a Valuable Serological Marker for Identification of Systemic Lupus Erythematosus Patients with Active Lupus Nephritis

OBJECTIVE

An early diagnosis of lupus nephritis (LN) has an important clinical implication in guiding treatments of systemic lupus erythematosus (SLE) in clinical settings. In this study, the diagnostic values of circulating autoantibodies to C1q alone or in combination with other markers for accessing active SLE and LN were evaluated.

METHODS

The diagnostic value of anti-C1q autoantibodies for identification of patients with active SLE disease and LN was evaluated by analyzing the level of anti-C1q antibodies in sera from 95 SLE patients, 40 non-SLE patients, and 34 healthy cohorts.

RESULTS

The prevalence of anti-C1q antibodies was significantly higher in patients with SLE (50/95, 52.6%), active SLE (40/51, 78.4%), and LN (30/35, 85.7%) in comparison with non-SLE patient controls, patients with inactive SLE, and non-LN, respectively. A combination of anti-C1q with anti-dsDNA and/or levels of complements C3 and C4 exhibited an increased specificity but a decreased sensitivity for identification of patients with active SLE and LN diseases relative to each of these markers alone.

CONCLUSION

Anti-C1q antibodies were strongly associated with disease activity and LN in SLE patients, suggesting that it may be a reliable serological marker for identification of SLE patients with active LN and active SLE disease.

C1q, antibodies and anti-C1q autoantibodies

The complement system has long been known for its role in combating infections. More recently the complement system is becoming increasingly appreciated for its role in processes that range from waste transport, immune tolerance and shaping of the adaptive immune response. Antibodies represent the humoral part of the adaptive immune response and the complement system interacts with antibodies in several ways. Activated complement fragments impact on the production of antibodies, the complement system gets activated by antibodies and complement proteins can be the target of (auto)antibodies. In this review, written to celebrate the contributions of Prof. Dr. M.R. Daha to the field of immunology and especially complement, we will focus on C1q and its various interactions with antibodies. We will specifically focus on the mechanisms by which C1q will interact with monomeric IgG versus polymerized IgG and fluid-phase IgM versus solid-phase IgM. In addition in this review we will discuss in detail how C1q itself is targeted by autoantibodies and how these autoantibodies are currently considered to play a role in human disease.

Anti-C1q antibodies as a follow-up marker in SLE patients

In cross-sectional studies autoantibodies against complement C1q (anti-C1q) were found to be highly associated with active lupus nephritis. The aim of this retrospective study was to determine the value of anti-C1q as follow-up marker of disease activity and renal involvement in patients with systemic lupus erythematosus (SLE). Fifty-two patients with SLE and a minimum of three anti-C1q measurements during follow-up were analyzed. Anti-C1q levels correlated with global disease activity scores. In subgroup analyses, patients without renal involvement did not show a significant correlation between anti-C1q levels and disease activity. In contrast, in patients with renal involvement, anti-C1q levels correlated well with global disease activity. In addition, a positive correlation with the urine protein-to-creatinine ratio and anti-dsDNA antibody levels as well as a negative correlation with complement levels was observed. Anti-C1q antibodies were found to strongly correlate with parameters of SLE disease activity during follow-up, in particular with regard to renal involvement.

Autoantibodies against complement C1q in patients with Behcet's disease: association with vascular involvement

AIM

The aim of our study was to determine the prevalence of anti-C1q antibodies and their possible association with clinical presentation in Behcet's disease (BD) patients with special emphasis for patients with vascular involvement.

METHODS

Plasma anti-C1q Abs levels were measured using an enzyme-linked immunosorbent assay in 51 BD patients and 25 age- and gender-matched healthy controls.

RESULTS

We found elevated concentrations of anti-C1q more frequently in patients with BD (18 %) than in healthy controls (8 %). The highest prevalence was found in patients with vascular BD (42 %) which was significantly higher than patients without vascular BD and healthy controls (p = 0.025). Furthermore, patients with vascular BD had the highest mean anti-C1q levels when compared to BD patients without vascular involvement or healthy control subjects (p = 0.015). We did not find significant differences in the prevalence of any other organ involvement between BD patients with elevated vs. normal anti-C1q ab levels. Anti-C1q ab levels positively correlated with ESR (r = 0.383, p = 0.006) and negatively with C4 (r = -0.304, p = 0.030).

CONCLUSION

In conclusion, we found an increased prevalence of anti-C1q autoantibodies in BD patients with vascular involvement. Further large scale longitudinal studies are required to assess and clarify the significance and the pathogenic role of anti-C1q antibodies in BD and other autoimmune diseases in which vasculitis is a component.

Systemic lupus erythematosus: epidemiology, pathophysiology, manifestations, and management

Systemic lupus erythematosus is a chronic autoimmune disorder characterized by production of autoantibodies directed against nuclear and cytoplasmic antigens, affecting several organs. Although cause is largely unknown, pathophysiology is attributed to several factors. Clinically, this disorder is characterized by periods of remission and relapse and may present with various constitutional and organ-specific symptoms. Diagnosis is achieved via clinical findings and laboratory examinations. Therapies are based on disease activity and severity. General treatment considerations include sun protection, diet and nutrition, smoking cessation, exercise, and appropriate immunization, whereas organ-specific treatments include use of steroidal and nonsteroidal anti-inflammatory drugs, immunosuppressive agents, and biologic agents.

Biomarkers in systemic lupus erythematosus: challenges and prospects for the future

The search for lupus biomarkers to diagnose, monitor, stratify, and predict individual response to therapy is currently more intense than ever before. This effort is essential for several reasons. First, epidemic overdiagnosis and underdiagnosis of lupus, even by certified rheumatologists, leads to errors in therapy with concomitant side effects which may be more serious than the disease itself. Second, identification of lupus flares remains as much an art as it is a science. Third, the capacity to stratify patients so as to predict those who will develop specific patterns of organ involvement is not currently possible but would potentially lead to preventive therapeutic strategies. Fourth, only one new drug for the treatment of lupus has been approved by the US Food and Drug Administration in over 50 years. A major obstacle in this pipeline is the dearth of biomarkers available to prove a patient has responded to an experimental therapeutic intervention. This review will summarize the challenges faced in the discovery and validation of lupus biomarkers, the most promising lupus biomarkers identified to date, and the promise of future directions.

Role of the clinical immunology laboratory in disease monitoring

Immunological investigations provide useful information to guide diagnosis of several disorders. Many such tests are also commonly repeated at intervals, in an effort to facilitate disease monitoring. In general however, immunology test results are often slow to alter. Furthermore, audit activity has indicated that repeated testing accounts for a substantial workload in many immunology services, which may waste resources and compromise the efficient completion of necessary tests. Consequently, the need and appropriate minimum interval between repeated testing requires critical evaluation. In this review, the clinical utility of repeated performance of several common immunology investigations has been evaluated, based upon published evidence. In some cases (e.g., paraprotein quantification, or measurement of anti-glomerular basement membrane antibodies), repeated testing provides vital clinical information and can be justified on a frequent and individualized basis. However, many other investigations provided by immunology services provide less valuable information when used to aid disease monitoring rather than diagnosis. It is hoped that the data summarized here will facilitate a more evidence-based approach to repeated testing. Such information may also assist with the local implementation of demand management strategies based upon setting of minimum retesting intervals for these investigations.

Anti-C1q autoantibodies, novel tests, and clinical consequences

Although anti-C1q autoantibodies have been described more than four decades ago a constant stream of papers describing clinical associations or functional consequences highlights that anti-C1q antibodies are still hot and happening. By far the largest set of studies focus on anti-C1q antibodies is systemic lupus erythematosus (SLE). In SLE anti-C1q antibodies associate with involvement of lupus nephritis in such a way that in the absence of anti-C1q antibodies it is unlikely that a flare in nephritis will occur. Anti-C1q antibodies occur in several autoimmune conditions but also in healthy individuals. Although considerable progress has been made in the understanding of how anti-C1q antibodies may contribute to tissue injury there is still a lot to learn about the processes involved in the breaking of tolerance to this protein. There has been considerable improvement in the assays employed to test for the presence of anti-C1q antibodies. Hopefully with these new and standardized assays at hand larger clinical association studies will be conducted with independent replication. Such large-scale studies will reveal the true value of clinical testing for anti-C1q autoantibodies in several clinical conditions.

Autoantibodies against complement C1q in patients with Behcet's disease: association with vascular involvement

AIM: The aim of our study was to determine the prevalence of anti-C1q antibodies and their possible association with clinical presentation in Behcet's disease (BD) patients with special emphasis for patients with vascular involvement. METHODS: Plasma anti-C1q Abs levels were measured using an enzyme-linked immunosorbent assay in 51 BD patients and 25 age- and gender-matched healthy controls. RESULTS: We found elevated concentrations of anti-C1q more frequently in patients with BD (18 %) than in healthy controls (8 %). The highest prevalence was found in patients with vascular BD (42 %) which was significantly higher than patients without vascular BD and healthy controls (p = 0.025). Furthermore, patients with vascular BD had the highest mean anti-C1q levels when compared to BD patients without vascular involvement or healthy control subjects (p = 0.015). We did not find significant differences in the prevalence of any other organ involvement between BD patients with elevated vs. normal anti-C1q ab levels. Anti-C1q ab levels positively correlated with ESR (r = 0.383, p = 0.006) and negatively with C4 (r = -0.304, p = 0.030). CONCLUSION: In conclusion, we found an increased prevalence of anti-C1q autoantibodies in BD patients with vascular involvement. Further large scale longitudinal studies are required to assess and clarify the significance and the pathogenic role of anti-C1q antibodies in BD and other autoimmune diseases in which vasculitis is a component.

Identification of a major linear C1q epitope allows detection of systemic lupus erythematosus anti-C1q antibodies by a specific peptide-based enzyme-linked immunosorbent assay

OBJECTIVE

Autoantibodies against C1q strongly correlate with the occurrence of severe nephritis in patients with systemic lupus erythematosus (SLE). We undertook this study to determine whether identification of the C1q epitope(s) recognized by these autoantibodies might lead to a better diagnostic assay and help elucidate the putative role of C1q and anti-C1q in SLE.

METHODS

SLE patient-derived anti-C1q Fab were used in a microarray-based peptide scan to identify the peptide sequence recognized by anti-C1q. Anti-C1q Fab binding to the target peptide was further analyzed using real-time interaction measurements (surface plasmon resonance) and peptide-based enzyme-linked immunosorbent assays (ELISAs).

RESULTS

A peptide scan of the collagen-like region of C1q identified 2 regions, 1 on the A chain and 1 on the B chain, that were the targets of the anti-C1q Fab. Binding was confirmed by surface plasmon resonance and showed nanomolar affinity. The A chain-derived peptide could specifically be detected in a peptide-based ELISA by SLE patient sera. Competition experiments suggested that this peptide represented one of the major linear epitopes of C1q that is the target of anti-C1q in SLE. Serum antibodies from most SLE patients but not from healthy individuals specifically bound to this epitope. Binding to the peptide correlated with binding of the same sera to native C1q but was found to be more sensitive for the detection of lupus nephritis.

CONCLUSION

We identified a major linear epitope of C1q that is the target of anti-C1q in SLE. The ELISA using this peptide was more specific and more sensitive than a conventional anti-C1q assay for the detection of active nephritis in SLE patients.

Evaluation of ENA-6 Profile by ELISA Immunoassay in Patients with Systemic Lupus Erythematodes

Autoimmune diseases occur in 3−5% of the population. Study included 30 patients with clinically diagnosed SLE and 30 healthy controls (American college of Rheumatology, 1997). SLE was diagnosed according to criteria issued in 1997 by the American College of Rheumatology (ACR). The aim of this study was to evaluate concentration values of each antigen of ENA-6 profile in SLE, to investigate possible correlation between the concentration of Sm antibodies and CIC, and to test their use as possible immunobiological markers in SLE. Furthermore, the aim of our study was to determine whether there is a correlation between Sm antibodies and CIC and SLE activity. The results revealed that all of these ENA-6 and Sm antibodies as biomarkers complement diagnoses of active SLE but their use as solo markers does not allow classifying patients with SLE. Our study has shown that based on calculations from ROC curves, Sm/RNP was clearly a very important marker for diagnosis of SLE (cut off ≥ 9.56 EU, AUC 0,942). The high incidence of Scl-70 (10%) reactivity suggests that ELISA monitoring of this antibody produces more false positive results than other multiplex assay. An important conclusion that can be drawn from the results of our study is that laboratory tests are no more effective than clinical examination for detecting disease relapse, but are helpful in the confirmation of SLE activity.

Emerging and critical issues in the pathogenesis of lupus

Systemic lupus erythematosus (SLE) is a multisystemic, autoimmune disease, encompassing either mild or severe manifestations. SLE was originally labeled as being an immune complex-mediated disease, but further knowledge suggested its pathogenesis is motlier than that, involving complex interactions between predisposed individuals and their environment. People affected with SLE have their immune system skewed toward aberrant self-recognition usually after encountering a triggering agent. Defeats in early and late immune checkpoints contribute to tolerance breakdown and further generation and expansion of autoreactive cell-clones. B and T cells play a master role in SLE, however clues are emerging about other cell types and new light is being shed on SLE autoantibodies, since some of them display really harmful potential (pathogenic antibodies), while others are just connected with disease development (pathological antibodies) and may even be protective. Autoantibody generation is elicited by abnormal apoptosis and inefficient clearance of cellular debris causing intracellular autoantigens (e.g. nucleosomes) to persist in the extracellular environment, being further recognized by autoreactive cells. Here we explore the complexity of SLE pathogenesis through five core issues, i.e. genetic predisposition, B and T cell abnormalities, abnormal autoantigen availability, autoantibody generation and organ damage, relying on current knowledge and recent insights into SLE development.

Role of serum anti-C1q antibodies as a biomarker for nephritis activity in pediatric and adolescent Egyptian female patients with SLE

Objective

To evaluate serum anti-C1q antibodies as a biomarker of systemic lupus erythematosus (SLE) flare and as a proposed noninvasive alternative to renal biopsy which is still the “gold standard” to determine renal activity in SLE.

Methods

Serum anti-C1q antibodies were measured in our patients (all were females), they were followed at the nephrology and pediatric nephrology units at the Faculties of Medicine of Cairo University and Misr University for science and technology (MUST). Our study included 120 patients in the pediatric and adolescent age group and they were categorized into three groups with (mean ± SD of 16.7 ± 3, 16.1 ± 2, 15.9 ± 3) respectively: Group 1 including 40 patients with SLE and active lupus nephritis; Group 2 including 40 patients with SLE and without active lupus nephritis, but with some extra renal activity mainly arthritis; and Group 3 including 40 healthy subjects.

Results

Anti-C1q antibodies were found to be significantly higher in patients with active lupus nephritis than those without active nephritis than control individuals with a median (range) of [27.5 (14 – 83), 9 (2.5 – 30), 7 (2 – 13)] respectively. In those with active lupus nephritis, anti-C1q was found to correlate significantly with other parameters assessing lupus nephritis activity like C3 (r = -0.33, p < 0.04), C4 (r = -0.32, p < 0.044), daily urinary protein excretion (r = 0.32, p < 0.036), renal SLEDAI (r = 0.64, p < 0.001), and activity index (r = 0.71, p < 0.001).

Conclusions

Anti-C1q antibodies can be used as a considerable marker for LN activity in that age group with 97.5% sensitivity and 65% specificity with the cutoff level 12 U/l. These levels are clearly higher than those for traditional markers of disease activity such as C3/C4 consumption and anti-dsDNA.

Mechanisms of tissue injury in lupus nephritis

Systemic lupus erythematosus is a prototypic autoimmune disease characterized by autoantibody production and immune complex formation/deposition in target organs such as the kidney. Resultant local inflammation then leads to organ damage. Nephritis, a major cause of morbidity and mortality in patients with lupus, occurs in approximately 50% of lupus patients. In the present review, we provide an overview of the current research and knowledge concerning mechanisms of renal injury in both lupus-prone mouse models and human lupus patients.

Basophils and the T helper 2 environment can promote the development of lupus nephritis

In systemic lupus erythematosus (SLE), self-reactive antibodies can target the kidney (lupus nephritis), leading to functional failure and possible mortality. We report that activation of basophils by autoreactive IgE causes their homing to lymph nodes, promoting T helper type 2 (T(H)2) cell differentiation and enhancing the production of self-reactive antibodies that cause lupus-like nephritis in mice lacking the Src family protein tyrosine kinase Lyn (Lyn(-/-) mice). Individuals with SLE also have elevated serum IgE, self-reactive IgEs and activated basophils that express CD62 ligand (CD62L) and the major histocompatibility complex (MHC) class II molecule human leukocyte antigen-DR (HLA-DR), parameters that are associated with increased disease activity and active lupus nephritis. Basophils were also present in the lymph nodes and spleen of subjects with SLE. Thus, in Lyn(-/-) mice, basophils and IgE autoantibodies amplify autoantibody production that leads to lupus nephritis, and in individuals with SLE IgE autoantibodies and activated basophils are factors associated with disease activity and nephritis.

Biomarkers for lupus nephritis: a critical appraisal

Kidney disease is one of the most serious manifestations of systemic lupus erythematosus (SLE). Despite the improvement in the medical care of SLE in the past two decades, the prognosis of lupus nephritis remains unsatisfactory. Besides exploring more effective but less toxic treatment modalities that will further improve the remission rate, early detection and treatment of renal activity may spare patients from intensive immunosuppressive therapies and reduce renal damage. Conventional clinical parameters such as creatinine clearance, proteinuria, urine sediments, anti-dsDNA, and complement levels are not sensitive or specific enough for detecting ongoing disease activity in the lupus kidneys and early relapse of nephritis. Thus, novel biomarkers are necessary to enhance the diagnostic accuracy and sensitivity of lupus renal disease, prognostic stratification, monitoring of treatment response, and detection of early renal flares. This paper reviews promising biomarkers that have recently been evaluated in longitudinal studies of lupus nephritis.