Autoantibodies to C-reactive protein in incomplete lupus and systemic lupus erythematosus

The Role of Anti-mCRP Autoantibodies in Lupus Nephritis

Background

Lupus nephritis is characterized by multiple autoantibodies production. However, there are few autoantibodies associated with disease activity and prognosis. CRP exists in at least two conformationally distinct forms: native pentameric C-reactive protein (pCRP) and modified/monomeric CRP (mCRP). Autoantibodies against mCRP are prevalent in sera of patients with lupus nephritis and are reported to be pathogenic.

Summary

The levels of serum anti-mCRP autoantibodies are associated with clinical disease activity, tubulointerstitial lesions, treatment response, and prognosis in patients with lupus nephritis. The key epitope of mCRP was amino acid 35-47. Furthermore, emerging evidence indicated that anti-mCRP autoantibodies could participate in the pathogenesis of lupus nephritis by forming in situ immune complexes or interfering with the biological functions of mCRP, such as binding to complement C1q and factor H.

Key Messages

Here, we review the recent advances in the prevalence, clinical-pathological associations, and potential pathogenesis of anti-mCRP autoantibodies in lupus nephritis, which may provide a promising novel therapeutic strategy for lupus nephritis.

Predicting progression from undifferentiated connective tissue disease to definite connective tissue disease: A systematic review and meta-analysis

PURPOSE

Undifferentiated connective tissue disease (UCTD) encapsulates a broad range of conditions including incomplete forms of systemic lupus erythematosus (SLE) and systemic sclerosis (SSc), some of whom progress to a formal clinical diagnosis over time. This systematic review (SR) and meta-analysis aimed to identify clinical and laboratory features and biomarkers that can predict progression of UCTD.

METHODS

A systematic literature search was carried out on MEDLINE, EMBASE and the Cochrane Central Register of Randomized Controlled Trials. Abstracts and full-text manuscripts were screened by two reviewers. Publications were included if they included at least 20 UCTD patients, a minimum of six months of follow up, and provided data on at least one risk factor for developing a defined CTD. The QUIPS tool was used to assess risk of bias (RoB) and GRADE for grading the quality of the evidence. The study is registered with PROSPERO (ID: CRD42021237725).

RESULTS

Fifty-nine studies were included in the SR, and forty-one in the meta-analysis. The predictors for progression to SLE with the highest certainty of evidence included those with younger age (MD -5.96 [-11.05-0.87 years]), serositis (RR 2.69 [1.61-4.51]), or the presence of anti-dsDNA antibodies (RR 4.27 [1.92-9.51]). For SSc, the highest certainty of evidence included puffy fingers (RR [3.09 [1.48-6.43]), abnormal nailfold changes (NFC) (avascular areas [RR 5.71 (3.03-10.8)] or active or late SSc pattern [RR 2.24 (1.25-4.01)] and anti-topoisomerase-I (RR 1.83 [1.45-2.30]). No novel biomarkers were included in the meta-analysis; however HLA molecules, regulatory T cell shift, pro-inflammatory cytokines and complement activation products were identified as potential predictors for evolution of disease.

CONCLUSIONS

Clinical and immunological parameters may predict which patients with UCTD progress to definitive disease; however, the heterogeneous nature and RoB in most studies limits the ability to apply these results in routine clinical practice. Limited data suggest that some novel biomarkers may provide additional predictive value but these will need larger well designed studies to fully delineate their clinical utility.

A Review of Anti-C Reactive Protein Antibodies in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE), the prototype autoimmune disease, is characterized by the production of a plethora of autoantibodies with various roles in the development of disease-related tissue damage. C-reactive protein (CRP) is an acute phase reactant with a pentameric structure. Under acidic or alkaline conditions, or when urea levels are high and/or calcium levels are low, the pentamer (pCRP) dissociates irreversibly into monomeric CRP (mCRP) and exposes new epitopes (neo-CRP). Importantly, anti-mCRP (but not anti-pCRP) antibodies have been described in patients with SLE, their prevalence varying from 4% to 78% in different cohorts. Numerous studies have investigated the relationship between autoantibodies directed against CRP (anti-CRP) and disease activity as well as their association with lupus nephritis (LN), frequently reporting discrepant findings. The main objective of the present review is to describe the role of anti-mCRP antibodies in SLE according to the currently available data.

Anti-Pentraxin Antibodies in Autoimmune Diseases: Bystanders or Pathophysiological Actors?

Pentraxins are soluble innate immunity receptors involved in sensing danger molecules. They are classified as short (CRP, SAP) and long pentraxin subfamilies, including the prototypic long pentraxin PTX3. Pentraxins act mainly as bridging molecules favoring the clearance of microbes and dead cells. They are also involved in many other biological processes, such as regulation of complement activation, inflammation and tissue homeostasis. Autoantibodies directed against pentraxins have been reported in various autoimmune diseases, especially in systemic lupus erythematosus and ANCA-associated vasculitis. In this review, we review the main biological characteristics and functions of pentraxins and summarize data concerning autoantibodies directed against pentraxins in the context of autoimmune diseases and discuss their potential pathological role.

Programmed Cell Death Pathways in the Pathogenesis of Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease characterized by excessive inflammatory and immune responses and tissue damage. Increasing evidence has demonstrated the important role of programmed cell death in SLE pathogenesis. When apoptosis encounters with defective clearance, accumulated apoptotic cells lead to secondary necrosis. Different forms of lytic cell death, including secondary necrosis after apoptosis, NETosis, necroptosis, and pyroptosis, contribute to the release of damage-associated molecular patterns (DAMPs) and autoantigens, resulting in triggering immunity and tissue damage in SLE. However, the role of autophagy in SLE pathogenesis is in dispute. This review briefly discusses different forms of programmed cell death pathways and lay particular emphasis on inflammatory cell death pathways such as NETosis, pyroptosis, and necroptosis and their roles in the inflammatory and immune responses in SLE.

The relationship between anti-C-reactive protein and disease activity in patients with systemic lupus erythematosus

BACKGROUND/AIMS

Anti-C-reactive protein (CRP) antibody has been introduced as a potential biologic marker in Systemic lupus erythematosus (SLE). The aim of study is to evaluate the level of anti-CRP antibody in patients with SLE.

METHODS

This study investigated the relationship between levels of anti-CRP antibodies and disease activity markers, such as complement, anti-double-stranded DNA antibody, and SLE disease activity index in 34 patients with SLE.

RESULTS

The serum anti-CRP antibody levels of the patients with SLE were significantly higher than those of the healthy controls (11.3 ± 5.6 µg/mL vs. 9.1 ± 2.8 µg/mL). The percentages of the positive anti-CRP antibody were 52.9% in SLE and 27.8% in controls. Disease duration of SLE showed significant correlation with the anti-CRP antibody (r = 0.234, p = 0.026). However no significant relationship was observed between the levels of anti-CRP antibodies and disease activity markers.

CONCLUSIONS

These data show that the anti-CRP antibody levels of the patients with SLE were significantly higher than those of healthy controls. We observed that the presence of the anti-CRP anti-CRP antibody was not associated with disease activity of SLE.

Clinical application of protein biomarkers in lupus erythematosus and lupus nephritis

Systemic lupus erythematosus (SLE) is a type of autoimmune disease that damages multiple organs, including the heart, joints, liver and kidneys. The main characteristics of SLE are the deposition of circulating autoantibodies; autoantigen complexes in the renal system; and abnormal expression of complements, cytokines and chemokines. Lupus nephritis (LN) is the most serious manifestation of SLE and is characterized by inflammation of the kidney. This review summarizes recent clinical applications of protein biomarkers including autoantibodies, complements, cytokines and chemokines and some new protein biomarkers in SLE and LN. The clinical differential diagnosis of protein biomarkers related to prognosis and diagnosis is discussed and highlighted. Protein biomarkers play crucial roles in the study of SLE and LN. Useful biomarkers will provide insights into effective treatments for these diseases.

Preclinical lupus

PURPOSE OF REVIEW

Systemic lupus erythematosus (SLE) is often preceded by immune dysregulation and clinical manifestations below the threshold for SLE classification. This review discusses current and evolving concepts about the preclassification period of SLE, including clinical and mechanistic observations, and potential avenues for early identification and intervention.

RECENT FINDINGS

Although incomplete lupus erythematosus (ILE) involves fewer clinical manifestations than SLE, ILE patients can suffer organ damage and early mortality. Common clinical features in ILE include antinuclear antibody seropositivity, polyarthritis, immunologic manifestations, and hematological disorders. Despite having lower disease activity and damage scores than SLE patients, ILE patients may develop pulmonary arterial hypertension, or renal, neurological, or peripheral vascular damage. The recently proposed Systemic Lupus International Collaborating Clinics SLE classification criteria could shift the period considered 'preclinical SLE'. Murine studies suggest that the balance of T-helper/T-regulatory cells, peroxisome proliferator-activated receptor γ activity, and plasmacytoid dendritic cell pathways may be valuable targets for early intervention.

SUMMARY

Advances in our understanding of early SLE, including stages before clinical features are fully developed, will improve our ability to identify individuals at high risk of classification for potential prevention trials, provide necessary information to improve diagnostic testing, and perhaps identify novel targets for directed therapeutics in clinical SLE.

Incomplete clearance of apoptotic cells in systemic lupus erythematosus: pathogenic role and potential biomarker

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease with repeated inflammation against multiple organs. Although its pathophysiology is not yet unveiled, uncleared apoptotic cells and their accumulation in tissue contribute to the autoimmune disturbance in SLE. Apoptosis is a programmed cell death process, which maintains tissue homeostasis and inhibits the development of any further immune response against apoptotic remnants. Earlier studies revealed that various 'eat-me' signals on apoptotic cells, bridging molecules and their receptors on phagocytes play a role in such a complicated process. Tyro3-Axl-Mer receptors, their bridging molecules, milk fat globulin epidermal growth factor-8, T-cell immunoglobulin mucin domain protein family, scavenger receptors, C1q, and pentraxins were found to be abnormal in SLE. In this review, apoptosis and clearance of its remnants are summarized, and the molecules involved in the incomplete clearance of apoptotic cells in SLE are discussed.