Differentiating VEXAS syndrome from cases of canonical forms of primary vasculitis remains a significant clinical challenge, particularly for ANCA-associated vasculitis (AAV). We reviewed the clinical features of VEXAS as an AAV mimicker, while adding three new cases to the existing literature.
Abstract Immunogenic responses against citrullinated antigens—proteins post-translationally modified by peptidylarginine deiminase (PAD) enzymes—are hallmark features of rheumatoid arthritis (RA). An important source of citrullinated autoantigens is leukotoxic hypercitrullination (LTH), a form of neutrophil cell death wherein cell membrane perforation results in PAD activation and subsequent widespread citrullination of antigens. In RA, citrullinated proteins can activate autoreactive adaptive immune cells, but their effect on antigen presenting cells is not well characterized. Here, we utilized differentiated HL-60s (dHL-60s), PAD-expressing neutrophil-like cells, killed by LTH as a cellular source of citrullinated antigens and evaluated their effect on monocyte-derived dendritic cells (moDCs). MoDCs co-cultured with LTH-killed dHL-60s upregulated activation markers, CD80 and CD83, by 2.5-fold more than moDCs alone. This activation was not observed in the absence of hypercitrullination, e.g. with live, apoptotic, or necrotic dHL-60s or with undifferentiated HL-60s. Inhibiting TLR4 and its endogenous ligand S100A9 prevented upregulation of CD83 on moDCs co-cultured with LTH-killed dHL-60s, suggesting that this effect is TLR4-dependent. Thus, LTH-killed neutrophils may create a pro-inflammatory environment by releasing S100A9, allowing moDCs presenting peptides from citrullinated proteins to upregulate co-stimulatory molecules and activate CD4+ T cells more potently.
Peptidylarginine deiminase IV (PAD4) post-translationally converts arginine residues in proteins to citrullines and is implicated in playing a central role in the pathogenesis of several diseases. Although PAD4 was historically thought to be a nuclear enzyme, recent evidence has revealed a more complex localization of PAD4 with evidence of additional cytosolic and cell surface localization and activity. However, the mechanisms by which PAD4, which lacks conventional secretory signal sequences, traffics to extranuclear localizations are unknown. In this study, we show that PAD4 was enriched in the organelle fraction of monocytes with evidence of citrullination of organelle proteins. We also demonstrated that PAD4 can bind to several cytosolic, nuclear and organelle proteins that may serve as binding partners for PAD4 to traffic intracellularly. Additionally, cell surface expression of PAD4 increased with monocyte differentiation into monocyte-derived dendritic cells and co-localized with several endocytic/autophagic and conventional secretory pathway markers, implicating the use of these pathways by PAD4 to traffic within the cell. Our results suggest that PAD4 is expressed in multiple subcellular localizations and may play previously unappreciated roles in physiological and pathological conditions. This article is part of the Theo Murphy meeting issue ‘The virtues and vices of protein citrullination’.
Interferon (IFN) is a key component of the innate immune response. For reasons that remain incompletely understood, the IFN system is upregulated in several rheumatic diseases, particularly those that feature autoantibody production, such as SLE, Sjögren’s syndrome, myositis and systemic sclerosis. Interestingly, many of the autoantigens targeted in these diseases are components of the IFN system, representing IFN-stimulated genes (ISGs), pattern recognition receptors (PRRs), and modulators of the IFN response. In this review, we describe features of these IFN-linked proteins that may underlie their status as autoantigens. Note is also made of anti-IFN autoantibodies that have been described in immunodeficiency states.
The origin and mechanisms of autoantigen generation in systemic lupus erythematosus (SLE) are poorly understood. Here, we identified SLE neutrophils activated in vivo by IFN as a prominent source of Ro52, also known as tripartite motif-containing protein 21 (TRIM21), a critical autoantigen historically thought to be primarily generated by keratinocytes in SLE. Different from mononuclear cells and keratinocytes, SLE neutrophils are enriched in several unique Ro52 species containing a core sequence encoded by exon 4 (Ro52Ex4) in TRIM21. Ro52Ex4 is the main target of anti-Ro52 antibodies and is found in 2 Ro52 variants (Ro52α and a potentially novel isoform termed Ro52γ) upregulated in SLE neutrophils. Further analysis of Ro52γ revealed a subset of autoantibodies against a unique C-terminal domain (Ro52γCT) generated from a frameshift due to the lack of exon 6 in Ro52γ. Antibodies to Ro52Ex4 and Ro52γCT distinguish SLE patient subsets characterized by distinct clinical, laboratory, treatment, and transcriptional profiles that are not discerned by the "classical" anti-Ro52 antibodies. These studies uncover IFN-activated neutrophils as a key source of unique immunogenic forms of Ro52 in SLE. Moreover, the finding of Ro52Ex4 and Ro52γCT as core targets of anti-Ro52 antibodies focus interest on Ro52γ as the potential isoform toward which immunological tolerance is initially lost in SLE.
Objective To evaluate the safety and utility of core needle biopsy (CNB) for diagnosis of salivary gland lymphoma in Sjögren’s syndrome (SS). Methods We analyzed data from consecutive SS patients who underwent ultrasound‐guided major salivary gland CNB for lymphoma diagnosis and determined whether CNB yielded an actionable diagnosis without need for further intervention. Results CNBs were performed in 24 patients to evaluate discrete parotid (n = 6) or submandibular (n = 2) gland masses or diffuse enlargement (n = 16; 15 parotid). One patient had 3 CNBs of the same mass. Of the 26 CNBs, 24 included flow cytometry, using CNB and/or fine needle aspirate material, and 14 targeted sonographically identified focal lesions. No patient reported complications. In the 23 patients with 1 CNB, final diagnoses were marginal zone lymphoma of mucosa‐associated lymphoid tissue (MALT; n = 6), atypical lymphoid infiltration (n = 3), benign lymphoepithelial sialadenitis (n = 9), normal gland tissue (n = 4), and lymphoepithelial cyst (n = 1). In the patient with serial CNBs, the initial one without flow cytometry was benign, but the next 2 showed atypical lymphoid infiltration. Monoclonal lymphoid infiltration was detected in 12 patients: 6 with MALT lymphoma, 3 were benign, and 3 with atypical lymphoid infiltration. Of the latter 3, 1 was treated with rituximab and 2 with expectant observation. The diagnosis changed from atypical lymphoid infiltration to MALT lymphoma in 1 patient following biopsy of inguinal adenopathy 6 months post‐CNB. CNB provided actionable results and avoided open excisional biopsies in all cases. Conclusion CNB is safe and useful in the evaluation of suspected salivary gland lymphoma in SS.
SARS-CoV-2 vaccination elicited high levels of immunogenicity in immunocompetent people in the original vaccine trials1 2 though recent studies have shown blunted immunogenicity in patients with rheumatic diseases treated with lymphocyte depleting agents.3 4 B-lymphocytes have been implicated in the pathogenesis of anti-neutrophil cytoplasmic antibidy (ANCA)-associated vasculitis (AAV) and B-cell-targeted therapy with rituximab is recognised as an established induction and maintenance strategy in management.5 6 SARS-CoV-2 infection in patients with AAV has been associated with severe outcomes,7 while rituximab has been associated with worse outcomes among patients infected with SARS-CoV-2.8 9 A recent study by Bonelli et al found evidence of an ameliorated humoral response but possible inducible cellular response in five patients treated with rituximab.10
We studied the tolerability and humoral response to the SARS-CoV-2 vaccine series in 48 patients with a diagnosis of AAV. Patients underwent SARS-CoV-2 antispike antibody testing to assess humoral response. Antibody testing was performed using antispike IgG enzyme immunoassay (Roche Elecsys via Quest, DiaSorin Liaison assay via LabCorp or Euroimmun via Hopkins lab). Demographics, clinical information including immunosuppressive therapy were extracted from medical records. Time from last rituximab administration to receipt of the first dose of the vaccine was recorded. We recorded serum creatinine, white blood cell count, serum immunoglobulins, Cluster of CD19 and …
Mass spectrometry of citrullinated proteins identified in monocyte organelles. Raw data including all protein and peptide hits, list of citrullinated peptides, citrullination site motif analysis, list of citrullinated proteins shared by all three donors, list of citrullinated organelle proteins, and the subsequent PANTHER analysis on the citrullinated organelle proteins identified are included.
