IgM ANCA in healthy individuals and in patients with ANCA-associated vasculitis

Circulating B cells display differential immune regulatory molecule expression in granulomatosis with polyangiitis

Granulomatosis with polyangiitis (GPA) is a B-cell-mediated, relapsing, autoimmune disease. There is a need for novel therapeutic approaches and relapse markers to achieve durable remission. B cells express immune regulatory molecules that modulate their activation and maintain tolerance. While recent studies show dysregulation of these molecules in other autoimmune diseases, data on their expression in GPA are limited. This study aimed to map the expression of surface immune regulatory molecules on circulating B-cell subsets in GPA and correlate their expression with clinical parameters. Immune regulatory molecule expression on circulating B-cell subsets was comprehensively examined in active GPA (n = 16), GPA in remission (n = 16), and healthy controls (n = 16) cross-sectionally using a 35-color B-cell-specific spectral flow cytometry panel. Our supervised and unsupervised in-depth analysis revealed differential expression of inhibitory and stimulatory immune molecules on distinct B-cell populations in GPA, with the most notable differences observed in active GPA. These differences include the upregulation of FcγRIIB on nonmature B cells, downregulation of CD21 and upregulation of CD86 on antigen-experienced B cells, and elevated CD22 expression on various populations. Additionally, we found a strong association between FcγRIIB, BTLA, and CD21 expression on specific B-cell populations and disease activity in GPA. Together, these findings provide novel insights into the immune regulatory molecule expression profile of B cells in GPA and could potentially form the foundation for new therapeutic approaches and disease monitoring markers.

Plasma exchange as an adjunctive therapy in anti-neutrophil cytoplasm antibody-associated vasculitis

INTRODUCTION

We summarize evidence for the role of therapeutic plasma exchange (TPE) in the treatment of anti-neutrophil cytoplasm antibody (ANCA)-associated vasculitis (AAV). TPE rapidly removes ANCA IgG, complement and coagulation factors important in the pathogenesis of AAV. TPE has been used in patients with rapidly deteriorating renal function to achieve early disease control, allowing time for immunosuppressive agents to prevent resynthesis of ANCA. The PEXIVAS trial challenged the utility of TPE in AAV, as it did not show benefit of adjunctive TPE on a combined end point of end stage kidney disease (ESKD) and death.

AREAS COVERED

We analyze data from PEXIVAS and other trials of TPE in AAV, an up-to-date meta-analysis, and recently published large cohort studies.

EXPERT OPINION

There remains a role for the use of TPE in AAV in certain groups of patients, in particular those with severe renal involvement (Cr >500 μmol/L or dialysis-dependent). It should be considered in patients with Cr >300 μmol/L and rapidly deteriorating function, or with life-threatening pulmonary hemorrhage. A separate indication is patients double positive for anti-GBM antibodies and ANCA. TPE may have the greatest benefit as part of steroid-sparing immunosuppressive treatment strategies.

Serum ANCA as Disease Biomarkers: Clinical Implications Beyond Vasculitis

Usually associated with autoimmune diseases, anti-neutrophil cytoplasmic antibodies are also detected in other conditions, such as infections, malignancies, and after intake of certain drugs. Even if the mechanisms of production and their pathogenic role have not been fully elucidated yet, ANCA are widely recognized as a clinically alarming finding due to their association with various disorders. While ANCA target several autoantigens, proteinase-3, and myeloperoxidase are the ones proved to be most frequently related to chronic inflammation and tissue damage in murine models. Albeit these autoantibodies could be present as an isolated observation without any implications, ANCA are frequently used in clinical practice to guide the diagnosis in a suspect of small vessel vasculitis. Conditions that should prompt the clinician to test ANCA status range from various forms of lung disease to renal or peripheral nervous system impairment. ANCA positivity in the presence of an autoimmune disease, especially rheumatoid arthritis, or connective tissue diseases, is frequently correlated with more clinical complications and treatment inefficacy, even in the absence of signs of vasculitis. For this reason, it has been postulated that ANCA could represent the final expression of an immune dysregulation rather than a pathogenic event responsible for organs damage. Recently, it has also been proposed that ANCA specificity (PR3 or MPO) could possibly define ANCA-associated vasculitides better than clinical phenotype. This review aims at summarizing the latest advancements in the field of ANCA study and clinical interpretation.

Fc receptors gone wrong: A comprehensive review of their roles in autoimmune and inflammatory diseases

Systemic autoimmune and inflammatory diseases have a complex and only partially known pathophysiology with various abnormalities involving all the components of the immune system. Among these components, antibodies, and especially autoantibodies are key elements contributing to autoimmunity. The interaction of antibody fragment crystallisable (Fc) and several distinct receptors, namely Fc receptors (FcRs), have gained much attention during the recent years, with possible major therapeutic perspectives for the future. The aim of this review is to comprehensively describe the known roles for FcRs (activating and inhibitory FcγRs, neonatal FcR [FcRn], FcαRI, FcεRs, Ro52/tripartite motif containing 21 [Ro52/TRIM21], FcδR, and the novel Fc receptor-like [FcRL] family) in systemic autoimmune and inflammatory disorders, namely rheumatoid arthritis, Sjögren's syndrome, systemic lupus erythematosus, systemic sclerosis, idiopathic inflammatory myopathies, mixed connective tissue disease, Crohn's disease, ulcerative colitis, immunoglobulin (Ig) A vasculitis, Behçet's disease, Kawasaki disease, IgG4-related disease, immune thrombocytopenia, autoimmune hemolytic anemia, antiphospholipid syndrome and heparin-induced thrombocytopenia.

Pathogenicity of Proteinase 3-Anti-Neutrophil Cytoplasmic Antibody in Granulomatosis With Polyangiitis: Implications as Biomarker and Future Therapies

Granulomatosis with polyangiitis (GPA) is a rare but serious necrotizing auto-immune vasculitis. GPA is mostly associated with the presence of Anti-Neutrophil Cytoplasmic Antibody (ANCA) targeting proteinase 3 (PR3-ANCA), a serine protease contained in neutrophil granules but also exposed at the membrane. PR3-ANCAs have a proven fundamental role in GPA: they bind neutrophils allowing their auto-immune activation responsible for vasculitis lesions. PR3-ANCAs bind neutrophil surface on the one hand by their Fab binding PR3 and on the other by their Fc binding Fc gamma receptors. Despite current therapies, GPA is still a serious disease with an important mortality and a high risk of relapse. Furthermore, although PR3-ANCAs are a consistent biomarker for GPA diagnosis, relapse management currently based on their level is inconsistent. Indeed, PR3-ANCA level is not correlated with disease activity in 25% of patients suggesting that not all PR3-ANCAs are pathogenic. Therefore, the development of new biomarkers to evaluate disease activity and predict relapse and new therapies is necessary. Understanding factors influencing PR3-ANCA pathogenicity, i.e. their potential to induce auto-immune activation of neutrophils, offers interesting perspectives in order to improve GPA management. Most relevant factors influencing PR3-ANCA pathogenicity are involved in their interaction with neutrophils: level of PR3 autoantigen at neutrophil surface, epitope of PR3 recognized by PR3-ANCA, isotype and glycosylation of PR3-ANCA. We detailed in this review the advances in understanding these factors influencing PR3-ANCA pathogenicity in order to use them as biomarkers and develop new therapies in GPA as part of a personalized approach.