Antineutrophil Antibody Research Articles

Hematological Side Effects of Psychiatric Drugs

This review article focuses on hematological disorders caused by psychiatric drugs, including neutropenia, leukopenia, leukocytosis, and anemia. Most major psychiatric drugs induce neutropenia and thrombocytopenia through various mechanisms, such as toxic bone marrow suppression and drug-dependent antineutrophil antibodies against hematopoietic precursors. Among these, agranulocytosis associated with phenothiazines is a well-discussed hematological side effect. Although rare, agranulocytosis is a dangerous and often fatal complication that may go unnoticed until infection occurs. We conducted a comprehensive literature search from 1977 to 2021, identifying 64 relevant articles. Our study aims to analyze outcomes related to pancytopenia, leucopenia, neutropenia, agranulocytosis, thrombocytopenia, and other hematological complications leading to hospitalization.

Natural history of chronic idiopathic neutropenia of the adult

Chronic idiopathic neutropenia (CIN) is a rare benign condition caused by an immune attack against neutrophils, either primary or in the context of other autoimmune conditions, lymphoproliferative syndromes, and inborn errors of immunity. In this single-center prospective study, 131 adult CIN patients were enrolled (median age 55 years, range: 20–93). At baseline, 56% had anti-neutrophil autoantibodies and 31% had autoimmune comorbidities. Over a median 3-year follow-up, the rate of grade ≥ 2 infections was 42%, with 10% grade ≥ 3, irrespective of neutrophil counts, demographics, and anti-neutrophil antibodies positivity, and G-CSF was used in 6 patients only. No malignant evolution nor deaths were observed. Bone marrow evaluation showed a large granular lymphocyte (LGL) infiltrate in 52%, mostly polyclonal, and hypocellularity in 31% of cases. Immune-histochemistry highlighted deposits of IgG, IgM, and complement fractions C3 and C4d in most cases. Interestingly, 19% of tested patients displayed somatic mutations of myeloid genes with an association with age. In conclusion, adult CIN appears to be a benign condition without life-threatening infections, yet deserving an extensive hematologic evaluation including bone marrow assessment to inform the differential diagnosis.

Response to Letter to the Editor: Tubulin beta is not the target of antineutrophil antibodies in primary sclerosing cholangitis.

Response to Letter to the Editor: Tubulin beta is not the target of antineutrophil antibodies in primary sclerosing cholangitis.

Tubulin beta 5 is not the target of antineutrophil antibodies in primary sclerosing cholangitis.

Tubulin beta 5 is not the target of antineutrophil antibodies in primary sclerosing cholangitis.

#1800 Cascade filtration in severe pulmonary-kidney syndrome: an one-center experience

Abstract Background and Aims In some forms of rapidly progressive glomerulonephritis (RPGN), the effect of plasma exchange (PE) is not well understood. Cascade filtration (CF) differs from standard PE in that it uses a double filter system, where the first filter is used to separate plasma from whole blood and the second filter is used to filter high-molecular weight substances. In this study, we investigated the efficacy and safety of CF in patients with ANCA-associated vasculitis (AAV) and Goodpasture's syndrome (GPS). Method During one year we included 18 patients with RPGN whose received CF in the study. The eligibility criteria was eGFR ≤15 ml/min/1.73 m2 and/or diffuse alveolar hemorrhage (DAH), presence of antineutrophilic antibodies or anti-GBM-antibodies. CF was performed on a Plasauto Sigma using a Plasmaflo OP-05W plasma separator and a Cascadeflo EC-30W separator with a fresh frozen plasma or 25% albumin solution. All patients received immunosuppressive therapy with steroids and cyclophosphamide, one patient with AAV received rituximab due to anemia and thromobocytopenia. All data were obtained from one hospitalization with the median of 43 days. Results Eight patients with AAV and three patients with GPS met the eligibility criteria. The median age of the patients in the AAV group was 59.8 (48; 66) years, with a female to male ratio of 1:1. All patients had evidence of systemic disease: seven patients had lung damage, including DAH, two patients had arthralgia, one had purpura and one had severe sinonasal involvement. The median creatinine level was 588 µmol/l (382; 1352), dialysis was initiated in 6 patients, and the median Birmingham Vasculitis Activity Score (BVAS) was 17 (15; 20). After three procedures of CF, all patients showed positive changes on CT scan, and dialysis was stopped in three patients. The immunological response to CF was observed quite rapidly in seven patients, with decreasing ANCA titer after three exchanges and decreasing antibody levels after six exchanges in one patient. There was a significant decrease in inflammatory markers, median C-reactive protein at baseline 179 (147; 226) decreased to 23 (2.8; 30.9) mg/l (p = 0.041). The CF was well tolerated with no significant adverse events. One patient receiving rituximab died after 4 months due to a severe COVID 19 infection. Three patients with GPS, one male 23 years old and two females 56 and 60 years old, also received CF. Creatinine concentrations at baseline were 1285, 1299 and 661 µmol/l, BVAS scores were 18, 20 and 15, respectively. After three procedures of CF, there was an immunological response: decrease in antibody levels from 121 U/ml to 15 U/ml, from 88.2 to 18.4 U/ml, from > 200.0 to 85.4 U/ml, CRP from 252 to 0.7 mg/l, from 120 to 5 mg/l, from 81.9 to 12.58 mg/l. There were no deaths and all three patients remained on dialysis. Conclusion CF was an effective and well tolerated method of treating severe AAV and GPS in addition to immunosuppressive treatment. Possibly due to the different filtration principle and the absence of donor plasma, we did not observe any infection-related adverse events and a lower number of procedures of CF was required compared to standard plasma exchanges. Further larger studies are needed to evaluate the benefits and safety of CF in combination with immunosuppressive treatment in RPGN patients.

Post-transplant CFHR5 mutation-related atypical HUS: The need for pre-transplant diagnosis

Atypical hemolytic uremic syndrome (aHUS) is a rare form of thrombotic microangiopathy (TMA) affecting multiple organs and can be sporadic or familial. It is most commonly caused by dysregulation of the alternative complement pathway. aHUS can occur at any age with a high rate of progression to end-stage kidney disease. We describe the case of a 24-year-old man with chronic kidney disease, severe hypertension, and antineutrophilic antibody by IF positive. On biopsy, diffuse global glomerulosclerosis with TMA and IF findings of full house pattern suggestive of lupus nephritis were present. Considering a lupus nephritis case, after 2 years of hemodialysis underwent live-related renal transplant (Father Donor). Immediate post-transplant period developed severe cortical necrosis and TMA. An etiological workup was done to ascertain the cause of post-transplant TMA. After excluding common causes of antibody-mediated rejection (C4d and donor-specific alloantibody neg), calcineurin inhibitor toxicity, and infection, we detected an abnormal complement CFHR5 mutation with an autosomal dominant pattern of inheritance. Pre-transplant diagnosis could have prevented taking the kidney from the father for transplant and further prevented recurrence. Systemic lupus erythematosus and TMA both can have alternate complement pathway dysregulation leading to full house IF pattern and misdiagnosis.

Late-onset and long-lasting neutropenias in the young: A new entity anticipating immune-dysregulation disorders.

This study identifies a new chronic form of immune neutropenia in the young with or without detectable indirect anti-neutrophil antibodies, characterized by mild/moderate neutropenia low risk of severe infection (14%), tendency to develop autoimmune phenomena over the course of the disease (cumulative incidence of 58.6% after 20 years of disease duration), leukopenia, progressive reduction of absolute lymphocyte count and a T- and B-cell profile similar to autoimmune disorders like Sjogren syndrome, rheumatoid arthritis, and systemic lupus erythematosus (increased HLADR+ and CD3 + TCRγδ cells, reduced T regulatory cells, increased double-negative B and a tendency to reduced B memory cells). In a minority of patients, P/LP variants related to primary immuno-regulatory disorders were found. This new form may fit the group of "Likely acquired neutropenia," a provisional category included in the recent International Guidelines on Diagnosis and Management of Neutropenia of EHA and EUNET INNOCHRON ACTION 18233. The early recognition of this form of neutropenia would help clinicians to delineate better specific monitoring plans, genetic counseling, and potentially targeted therapies.

Neutrophil depletion attenuates acute renal injury after exhaustive exercise in mice.

Prolonged intense exercise induces acute renal injury; however, the precise mechanism remains unclear. We investigated the effects of neutrophil depletion in male C57BL/6J mice. Male C57BL/6J mice were divided into four groups: sedentary with control antibody; sedentary with antineutrophil antibody; exhaustive exercise with control antibody; and exhaustive exercise with antineutrophil antibody. Antineutrophil (1A8) or control antibody was administered i.p. to the mice before they ran on a treadmill. Plasma levels of creatinine and blood urea nitrogen (BUN) were measured. Renal histology was assessed 24h after exhaustive exercise, and the concentration of kidney injury molecule (KIM)-1 was measured using an enzyme-linked immunosorbent assay. The expression levels of inflammatory cytokines were measured using qRT-PCR. Furthermore, NADPH oxidase activity and the hydrogen peroxide concentration in the kidney were measured. Immediately after exhaustive exercise, plasma BUN was significantly increased, but creatinine was not. The increase in BUN after exercise was suppressed by 1A8 treatment. The pathological changes manifested as congested and swollen glomeruli and nuclear infiltration after exhaustive exercise. These changes were suppressed by treatment with the 1A8 antibodies. The KIM-1 concentration increased after exhaustive exercise but was reduced by the 1A8 antibodies. Treatment with the 1A8 antibody also decreased exhaustive exercise-induced inflammation and reactive oxygen species levels in the kidney. These results suggest that neutrophils contribute to exercise-induced acute renal injury by regulating inflammation and oxidative stress.

Severe Chronic Idiopathic Neutropenia Managed with Chronic Filgrastim: A Case Report

Myelodysplastic syndrome (MDS) represents a heterogeneous group of hematological disorders characterized by ineffective hematopoiesis and abnormal blood cell production. Chronic neutropenia is one such MDS and is classified into mild (Absolute Neutrophil Count (ANC): 1,000 to 1,500/µL), moderate (ANC: 500 to 1,000/µL), or severe (ANC: below 500/µL), with the latter posing the highest risk of infection-related complications. In an attempt to alleviate neutropenia, patients with MDS are often treated with colony stimulating factors (CSFs), such as filgrastim to promote growth and maturation of neutrophils. The target ANC is 1,500 to 2,000/µL for adequate protection against most infections. However, CSF treatments have the potential to stimulate the transformation of MDS into acute myeloid leukemia (AML) so CSF is often used with caution. Presented below is a case of severe chronic idiopathic neutropenia responsive to chronic filgrastim that has yet to show evidence of transformation. A 79 year-old female with a past medical history of distant tobacco use, hypertension, acute cerebrovascular accident, and Hashimoto's thyroiditis presents to the clinic for routine follow-up of her now stable chronic idiopathic neutropenia being managed with weekly filgrastim injections for three weeks with one week off in between cycles. She had originally presented to medical attention in 2004 complaining of chronic mouth sores and ulcers with leukopenia and a severely decreased ANC of <500/µL. Continued monitoring with more than 3 complete blood counts (CBC) with a differential consistently noted a decreased ANC in the setting of persisting oral mucosal erosion. Leukocytes were not noted to be dysplastic, quantitative IgG, IgA, IgM levels were noted to be within normal limits, anti-nuclear antibodies/ anti-neutrophil antibodies were noted to be negative argued against an etiology of large granular lymphocytic leukemia, immunodeficiency, and/or autoimmune disorders, respectively. A trial of glucocorticoids did not significantly increase her ANC which led to her ultimately receiving a bone marrow biopsy (BMB) in 2008. A mildly hypercellular marrow with trilineage hematopoiesis was found, with maturation of all lines, negative flow cytometry, and myelodysplasia. Comforted by the lack of MDS pathologically, the patient was started on filgrastim with significant improvement. Over the course of years the frequency and duration of filgrastim was optimized to her current regimen of weekly filgrastim injections for 3 weeks followed by one week off which allowed her to maintain an adequate ANC and avoid oral ulcers to this day. Despite the feared complication of kickstarting the transformation of MDS into AML with CSF therapy, patients such as the one mentioned here can benefit greatly from judicious use of CSF when blood work can be monitored for complications. The use of G-CSF in severe chronic neutropenia to raise levels from below 500/µL to the ideal target ANC is 1,500 to 2,000 cells per microliter (µL) for adequate protection is in line with our current understanding that even long-term use of G-CSF does not appear to increase the risk of AML (Dale et al., 2022). G-CSF should continue to be considered in the management of severe chronic neutropenia as the risk for transformation may be insignificant compared to the clinical benefit of its use when properly monitored.

Heterogeneous Genetic Landscape of Chronic Idiopathic Neutropenia Revealed By Whole Exome Sequencing

Background: Adultpatients with persistent, unexplained neutropenia who do not fulfill the diagnostic criteria of any underlying disease are characterized as chronic idiopathic neutropenia (CIN) cases.It is an exclusion diagnosis that can be established after a thorough clinical/laboratory investigation for any underlying causes, including negative anti-neutrophil antibody testing, inconclusive bone marrow (BM) aspiration/biopsy and normal cytogenetics. CIN patients regardless of their absolute neutrophil counts (ANC) usually display a benign and uncomplicated clinical course. Although the pathogenesis of CIN remains largely unknown, we hypothesize that a constitutional/congenital background might exist, at least in some cases, that have potentially escaped diagnosis during childhood. Aim of the study: To investigate the genetic landscape of neutropenia in CIN by conducting whole exome sequencing (WES) analysis in a number of adult CIN patients. Methods: We have performed WES in 16 adult (median age 59 years, range 30-72 years) patients (11 females and 5 males) with CIN according to previously published criteria (Fioredda F, et al Hemasphere. 2023). The patients had median ANC 1.2 x 10 9/L (range 0.4-1.6 x 10 9/L) for prolonged period and unknown neutropenia onset in most cases. Genomic DNA was extracted from peripheral blood samples, coding fragment libraries were prepared, sequencing performed on Illumina NovaSeq 6000 System, and data subjected to an in-house pipeline for bioinformatic analysis for variant calling and annotations. Singleton analyses were performed focusing on genes associated with congenital defects of phagocytes, BM failure (BMF) and immune deficiency and dysregulation. Mean depth of coverage was 70x and the mean number of variants/sample was 22553. Results: WES analysis identified 10 pathogenic/likely pathogenic (P/LP) variants in 10 patients. The variants consisted of 4 frameshift mutations, 3 nonsense mutations, 1 missense mutation, 1 splice-site mutation and 1 splice-region mutation. Pathogenic variants in congenital neutropenia (CN)-related genes included only a heterozygous mutation in G6PC3:c.511C>T,p.Gln171Ter (previously detected in one of our CN patients; Nikolouzakis TK et al, Ann Hematol. 2022). Pathogenic variants in genes associated with BMF were detected in two genes, namely FANCM:c.1492C>T, p.Gln498Ter and CTC1:c.3058C>T,p.Gln1020Ter, respectively. The majority of the pathogenic variants were found in genes associated with immune deficiency and dysregulation. These involved: (i) a heterozygous mutation in DCLRE1C:c.1784dup,p.Ile596fs (associated with immunodeficiencies affecting cellular and humoral immunity); (ii) a LP mutation in ORAI1:c.132_133del,p. Arg45fs and a pathogenic variant in SPINK5:c.1302+4A>T (related to combined immunodeficiencies with associated or syndromic features); (iii) a pathogenic variant in MEFV:c.2080A>G, p.Met694Val and a LP variant in PSMG2:c.703-2A>T (both genes associated with autoinflammatory disorders); (iv) a LP variant in IRF7:c.1089dup,p.Pro364Alafs (associated with defects in intrinsic and innate immunity); and (v) a LP variant in PEPD:c.738_739insGT,p.Ser247fs (associated with immune dysregulation). Regarding variants of undetermined significance (VUS) an average of 4.5 VUS variants per patient were detected in genes related to CN ( HAX1, VPS13B, LYST), BMF ( GATA2, SAMD9, CXCR4) or immunodeficiency ( TCF3). However, none of these patients display clinical symptoms typical of these conditions. Specifically, the majority of the patients presented with mild/moderate neutropenia and rarely with severe neutropenia, they have relatively normal BM biopsies and do not display major symptoms or signs related to severe immunodeficiency or immune dysregulation syndromes. Conclusions: This study is the first attempt of WES analysis in adult CIN patients and shows that there is a heterogeneous genetic landscape underlying the disease. More studies are required so that the detected P/LP variants and VUS can be associated with the clinical phenotypes to more accurately interpret their potential contribution to the neutropenia phenotype.

Using an artificial intelligence tool incorporating natural language processing to identify patients with a diagnosis of ANCA-associated vasculitis in electronic health records

BackgroundBecause anti-neutrophil cytoplasmatic antibody (ANCA)-associated vasculitis (AAV) is a rare, life-threatening, auto-immune disease, conducting research is difficult but essential. A long-lasting challenge is to identify rare AAV patients within the electronic-health-record (EHR)-system to facilitate real-world research. Artificial intelligence (AI)-search tools using natural language processing (NLP) for text-mining are increasingly postulated as a solution. MethodsWe employed an AI-tool that combined text-mining with NLP-based exclusion, to accurately identify rare AAV patients within large EHR-systems (>2.000.000 records). We developed an identification method in an academic center with an established AAV-training set (n = 203) and validated the method in a non-academic center with an AAV-validation set (n = 84). To assess accuracy anonymized patient records were manually reviewed. ResultsBased on an iterative process, a text-mining search was developed on disease description, laboratory measurements, medication and specialisms. In the training center, 608 patients were identified with a sensitivity of 97.0 % (95%CI [93.7, 98.9]) and positive predictive value (PPV) of 56.9 % (95%CI [52.9, 60.1]). NLP-based exclusion resulted in 444 patients increasing PPV to 77.9 % (95%CI [73.7, 81.7]) while sensitivity remained 96.3 % (95%CI [93.8, 98.0]). In the validation center, text-mining identified 333 patients (sensitivity 97.6 % (95%CI [91.6, 99.7]), PPV 58.2 % (95%CI [52.8, 63.6])) and NLP-based exclusion resulted in 223 patients, increasing PPV to 86.1 % (95%CI [80.9, 90.4]) with 98.0 % (95%CI [94.9, 99.4]) sensitivity. Our identification method outperformed ICD-10-coding predominantly in identifying MPO+ and organ-limited AAV patients. ConclusionsOur study highlights the advantages of implementing AI, notably NLP, to accurately identify rare AAV patients within large EHR-systems and demonstrates the applicability and transportability. Therefore, this method can reduce efforts to identify AAV patients and accelerate real-world research, while avoiding bias by ICD-10-coding.

Mucosal-associated invariant T cells contribute to suppression of inflammatory myeloid cells in immune-mediated kidney disease

Mucosal-associated invariant T (MAIT) cells have been implicated in various inflammatory diseases of barrier organs, but so far, their role in kidney disease is unclear. Here we report that MAIT cells that recognize their prototypical ligand, the vitamin B2 intermediate 5-OP-RU presented by MR1, reside in human and mouse kidneys. Single cell RNAseq analysis reveals several intrarenal MAIT subsets, and one, carrying the genetic fingerprint of tissue-resident MAIT17 cells, is activated and expanded in a murine model of crescentic glomerulonephritis (cGN). An equivalent subset is also present in kidney biopsies of patients with anti-neutrophil cytoplasmatic antibody (ANCA)-associated cGN. MAIT cell-deficient MR1 mice show aggravated disease, whereas B6-MAITCAST mice, harboring higher MAIT cell numbers, are protected from cGN. The expanded MAIT17 cells express anti-inflammatory mediators known to suppress cGN, such as CTLA-4, PD-1, and TGF-β. Interactome analysis predicts CXCR6 – CXCL16-mediated cross-talk with renal mononuclear phagocytes, known to drive cGN progression. In line, we find that cGN is aggravated upon CXCL16 blockade. Finally, we present an optimized 5-OP-RU synthesis method which we apply to attenuating cGN in mice. In summary, we propose that CXCR6+ MAIT cells might play a protective role in cGN, implicating them as a potential target for anti-inflammatory therapies.

Two Cases of Perinuclear Anti-neutrophil Cytoplastic Antibodies Associated Hypertrophic Pachymeningitis Presented with Visual Loss

Pachymeningitis is an inflammatory process mainly involving the dura mater and is possibly associated with infectious, neoplastic, or autoimmune disease. However, in most cases, the etiology remains unknown. Clinical manifestations of pachymeningitis can vary, ranging from headache, cranial neuropathy, cerebellar dysfunction, to seizure. Here we report two cases of perinuclear anti-neutrophil cytoplasmic antibodies associated with pachymeningitis, in both the visual loss attributed to optic neuropathy was the primary sign.

Felty's syndrome.

Felty's syndrome was first described in 1924 by the US-American physician Augustus Roi Felty as a triad of rheumatoid arthritis, splenomegaly and leucopenia. Even nearly 100 years later, this rare syndrome is still paralleled by diagnostic and therapeutic challenges and its pathogenesis is incompletely understood. Neutropenia with potentially life-threatening infections is the main problem and several pathomechanisms like Fas-mediated apoptosis, anti-neutrophil antibodies, anti-G-CSF antibodies, neutrophil consumption in the context of NETosis and suppression of granulopoiesis by T-LGLs have been suggested. Felty's syndrome has various differential diagnoses as splenomegaly and cytopenia are common features of different infectious diseases, malignancies and autoimmune disorders. Additionally, benign clonal T-/NK-LGL lymphocytosis is increasingly noticed in Felty's syndrome, which further complicates diagnosis. Today's treatment options are still sparse and are largely based on case reports and small case series. Methotrexate is the mainstay of therapy, followed by rituximab, but there is less evidence for alternatives in the case of adverse reactions or failure of these drugs. This article gives an updated review about Felty's syndrome including its pathogenesis and treatment options.

Vasculitis oft the skin after cocaine use

A 20-years-old patient presented himself to our emergency room with extensive and extremely painful purpura with necrotizing spots and blisters, especially on the lower extremities, but also on the arms, trunk and ears. There was a pre-existing use of cocaine. Laboratory tests showed increased signs of inflammation as well as an increase in proteinase 3- and myeloperoxidase-ANCA (Anti-neutrophil cytoplasmatic antibody). In combination with the medical history, the clinical findings, and the laboratory values, vasculitis of the skin after cocaine use was revealed. Under therapy with steroids and cocaine abstinence, there was a regression of the changes. Vasculitis is a serious complication of cocaine use.

Low levels of complement factor C3 at diagnosis can predict outcome in antineutrophil antibody associated vasculitis.

Experimental data support the involvement of complement in the pathogenesis of antineutrophil antibody associated vasculitis, and clinical studies describe a more severe disease phenotype in patients with antineutrophil antibody associated vasculitis and complement activation. In the present study, we looked for an association between circulating serum complement factor 3 levels at diagnosis and outcomes. One hundred sixty-four patients with antineutrophil antibody associated vasculitis who underwent kidney biopsy at our center during the last 15years were retrospectively reviewed. Patients were categorized according to their serum complement factor 3 level at diagnosis. Patient and renal survival were compared between those above and below the median serum complement factor 3 at diagnosis. During the first year, 6 patients died and 53 reached end-stage renal disease. Death or end-stage renal disease at one-year were significantly more common in the low serum complement factor 3 group (44 vs. 29%, p = 0.037). In the multivariable analysis, serum complement factor 3 was the strongest negative outcomepredictor (HR, 95%CI 0.118, (0.021-0.670)). The lower the serum complement factor 3 level at baseline, the higher the risk of dialysis and death. The risk was particularly high for both endpoints if the serum complement factor 3 concentration was below 0.9g/l at baseline. Complement activation at diagnosis may identify a distinct subgroup of patients with antineutrophil antibody associated vasculitis and higher risk for poor outcomes. However, it remains to be proven whether inhibition of serum complement factor 3 is beneficial and safein the clinical setting.

Anti-Neutrophil Extracellular Trap Antibodies in Antiphospholipid Antibody-Positive Patients: Results From the Antiphospholipid Syndrome Alliance for Clinical Trials and InternatiOnal Networking Clinical Database and Repository.

This study aimed to elucidate the presence, antigen specificities, and potential clinical associations of anti-neutrophil extracellular trap (anti-NET) antibodies in a multinational cohort of antiphospholipid (aPL) antibody-positive patients who did not have lupus. Anti-NET IgG/IgM levels were measured in serum samples from 389 aPL-positive patients; 308 patients met the classification criteria for antiphospholipid syndrome. Multivariate logistic regression with best variable model selection was used to determine clinical associations. For a subset of the patients (n=214), we profiled autoantibodies using an autoantigen microarray platform. We found elevated levels of anti-NET IgG and/or IgM in 45% of the aPL-positive patients. High anti-NET antibody levels are associated with more circulating myeloperoxidase (MPO)-DNA complexes, which are a biomarker of NETs. When considering clinical manifestations, positive anti-NET IgG was associated with lesions affecting the white matter of the brain, even after adjusting for demographic variables and aPL profiles. Anti-NET IgM tracked with complement consumption after controlling for aPL profiles; furthermore, patient serum samples containing high levels of anti-NET IgM efficiently deposited complement C3d on NETs. As determined by autoantigen microarray, positive testing for anti-NET IgG was significantly associated with several autoantibodies, including those recognizing citrullinated histones, heparan sulfate proteoglycan, laminin, MPO-DNA complexes, and nucleosomes. Anti-NET IgM positivity was associated with autoantibodies targeting single-stranded DNA, double-stranded DNA, and proliferating cell nuclear antigen. These data reveal high levels of anti-NET antibodies in 45% of aPL-positive patients, where they potentially activate the complement cascade. While anti-NET IgM may especially recognize DNA in NETs, anti-NET IgG species appear to be more likely to target NET-associated protein antigens.

Heterozygous TCF3-Related Disease Presenting as X-linked Agammaglobulinemia Mimicry in a Male Toddler with B-cell Aplasia, Agammaglobulinemia, and Severe Neutropenia

IntroductionDisease associated with TCF3 variants are rare and associated with autosomal dominant inheritance agammaglobulinemia. Patients present with profound reduction in CD19+ cells and a block in B cell development at the common lymphoid precursor to pro–B cell phase of differentiation. Severe neutropenia is frequently described in X-linked agammaglobulinemia (XLA) patients but not yet described as a presenting finding in TCF3-related disease. Case ReportThis case describes a 13-month-old full term male with a history of reactive airway disease and recurrent infections including multiple bouts of acute otitis media, hand -foot-mouth, and viral upper respiratory illnesses who presented with fever and persistent severe neutropenia (absolute neutrophil count <100 cell/uL) necessitating hospital admission. Given his infectious history and severe neutropenia, he underwent evaluation for an underlying inborn error of immunity with the following pertinent findings: undetectable IgG (<16 mg/dL), IgM (<10 mg/dL), IgA (<2 mg/dL) and IgE (<2 kU/L), negative pneumococcal, tetanus and diphtheria vaccine titers despite vaccination, lymphocyte subsets with normal CD3, CD4, CD8, and CD16/56 absolute values but extremely low CD19 level (38 cells/cmm), and negative anti-neutrophil antibodies. Patient Bruton tyrosine kinase (Btk) protein flow cytometry results in monocytes were similar to an experimental control, while B-cell subset analysis was unable to be obtained given low B-cell numbers. Comprehensive genetic testing subsequently identified a heterozygous pathogenic TCF3 variant, c.1663G>A, p. (Glu555Lys). Following initiation of intravenous immunoglobulin (IVIG) replacement, our patient's neutropenia resolved quickly and completely. He continues to receive monthly IVIG with goal IgG troughs >800 mg/dL and resultant significant improvement in infections. ConclusionAs in XLA, our patient's severe neutropenia rapidly resolved with initiation of immunoglobulin replacement. While it has been shown that neutrophil development is somewhat dependent on the Btk protein, further study into the importance of the TCF3 protein and additionally adequate immunoglobulin levels in neutrophil expansion is needed. Finally, germline inborn errors of immunity, including TCF3 variants, should be considered in children with a history of recurrent infections and persistent neutropenia.

P100 Atypical Anti-Neutrophil Cytoplasmatic Antibodies Are Antibodies Against Neutrophil Extracellular Traps: A Novel Pathophysiological Mechanism In Ulcerative Colitis

Abstract Background The number of mucosal neutrophils, as well as the presence of neutrophil extracellular traps (NETs), correlate with disease activity in Ulcerative colitis (UC), an inflammatory bowel disease. Most (~80%) UC patients present atypical Anti-Neutrophil Cytoplasmatic Antibodies (a-ANCAs) to a yet unknown antigen, which shows a different immunofluorescence staining pattern when compared to cytoplasmatic (c-ANCA) and perinuclear (p-ANCA) that target proteinase (PR3) and myeloperoxidase (MPO), respectively. Here, we analyzed whether a-ANCAs specifically bind to NETs. Methods Blood neutrophils were treated to form non-lytic NETs using LPS-treated platelets with and without DNAse and Trypsin. Patient biopsies and in vitro-formed non-lytic NETs were incubated with p-ANCA, c-ANCA and a-ANCA positive patient and ANCA negative control serum and processed for immunofluorescence microscopy. Macrophage-mediated clearance of serum-pretreated NETs was analyzed in real-time using Incucyte microscopy. Results Ethanol-fixed neutrophils displayed c-ANCA, p-ANCA patterns, and a-ANCA web-like staining. Only c- and p-ANCA react to DNAse-treated ethanol-fixed neutrophils (Fig 1). Serum containing a-ANCA’s bound to non-lytic NETs that disappeared upon treatment with DNAse and Trypsin whereas c- and p- ANCA binding did not disappear upon DNAse treatment (Fig 2) indicating that both DNA and proteins are needed for a-ANCAs to bind to non-lytic NETs. In inflamed colonic tissue of UC patients, a-ANCA co-stained with extracellular DNA and neutrophil elastase covering the intestinal epithelium (Fig 3). In vitro, NETs were efficiently cleared by macrophages, which was strongly inhibited after pre-incubating with a-ANCAs (Fig 4). Macrophages exposed to a-ANCA-incubated NETs expressed higher CXCL-8 and IFN-B levels than the NETs exposed to control serum (both p&amp;lt;0.05). Figure 1 Figure 2 Figure 3 Figure 4 Conclusion a-ANCAs specifically bind to de novo DNA-protein antigens in non-lytic NETs, which prevents efficient macrophage-mediated clearance and induces a pro-inflammatory (M1) phenotype. This inflammatory milieu may contribute to the pathophysiology of UC.

An autopsy case of polyarteritis nodosa accompanied with multiple immune-specific autoantibodies and rhabdomyolysis

A 72-year-old male complained of fever lasting 1 month and developed muscle weakness and paresthesia in the legs. He presented with muscle weakness, grasping pain, decreased deep tendon reflexes in the extremities, and reduction of tactile sensation in the distal parts of the left leg muscles. Blood tests revealed leukocytosis and inflammatory reactions. Collagen-disease-specific autoantibodies including anti-double-stranded DNA and anti-Scl-70 antibodies were positive, but antineutrophil cytoplastic antibodies were negative. Nerve conduction studies revealed asymmetric axonal degeneration, indicating multiple mononeuropathy. We started intravenous methylprednisolone pulse and plasma exchange therapies. However, the patient developed intestinal necrosis and perforation, and he died 44 days after the onset of fever. An autopsy revealed vasculitis in small- to medium-sized vessels in multiple organs as well as myoglobin casts in the renal tubules, which were suggestive polyarteritis nodosa (PAN) accompanied with rhabdomyolysis. Positivity for collagen-disease-specific autoantibodies and accompanying rhabdomyolysis are atypical findings with PAN. This patient was not clinically diagnosed as PAN, and so promptly starting immunotherapies should be considered when a case presents with evidence of vasculitis.