Antigen-driven Disease Research Articles

Mononuclear cell composition and activation in blood and mucosal tissue of eosinophilic esophagitis.

Eosinophilic esophagitis (EoE) is a chronic, inflammatory, antigen-driven disease of the esophagus. Tissue EoE pathology has previously been extensively characterized by novel transcriptomics and proteomic platforms, however the majority of surface marker determination and screening has been performed in blood due to mucosal tissue size limitations. While eosinophils, CD4+ T cells, mast cells and natural killer (NK) T cells were previously investigated in the context of EoE, an accurate picture of the composition of peripheral blood mononuclear cells (PBMC) and their activation is missing. In this study, we aimed to comprehensively analyze the composition of peripheral blood mononuclear cells and their activation using surface marker measurements with multicolor flow cytometry simultaneously in both blood and mucosal tissue of patients with active EoE, inactive EoE, patients with gastroesophageal reflux disease (GERD) and controls. Moreover, we set out to validate our data in co-cultures of PBMC with human primary esophageal epithelial cells and in a novel inducible mouse model of eosinophilic esophagitis, characterized by extensive IL-33 secretion in the esophagus. Our results indicate that specific PBMC populations are enriched, and that they alter their surface expression of activation markers in mucosal tissue of active EoE. In particular, we observed upregulation of the immunomodulatory molecule CD38 on CD4+ T cells and on myeloid cells in biopsies of active EoE. Moreover, we observed significant upregulation of PD-1 on CD4+ and myeloid cells, which was even more prominent after corticosteroid treatment. With co-culture experiments we could demonstrate that direct cell contact is needed for PD-1 upregulation on CD4+ T cells. Finally, we validated our findings of PD-1 and CD38 upregulation in an inducible mouse model of EoE. Herein we show significant alterations in the PBMC activation profile of patients with active EoE in comparison to inactive EoE, GERD and controls, which could have potential implications for treatment. To our knowledge, this study is the first of its kind expanding the multi-color flow cytometry approach in different patient groups using in vitro and in vivo translational models.

SUCCESSFUL TREATMENT OF REFRACTORY PEDIATRIC EOSINOPHILIC ESOPHAGITIS WITH DUPILUMAB

<h3>Introduction</h3> Eosinophilic esophagitis (EoE) is a chronic T-helper 2 (Th2) antigen driven disease characterized by eosinophilic infiltrates in the esophageal mucosa. Currently, there are no therapies approved by the United States Food and Drug Administration (FDA) for EoE in patients under twelve years of age. Expert guidance recommends the use of proton pump inhibitors (PPI), swallowed corticosteroids, elimination diets, and esophageal dilation<i>.</i> However, these interventions do not ameliorate symptoms and eosinophilic inflammation in all cases. Herein, we describe the successful treatment of a ten-year-old patient with EoE refractory to guideline-directed therapy with dupilumab. <h3>Case Description</h3> Our patient is a ten-year-old male with failure to thrive and EoE refractory to dietary change, swallowed corticosteroids, and PPI therapy. Due to the severity of his disease, the patient was initiated on monthly dupilumab injections. Following 6 months of dupilumab therapy (300mg subcutaneously Q4 weeks) he experienced endoscopic and histologic remission (0 eos/hpf). He remained in clinical and histologic remission more than 3 months after milk was reintroduced into the diet. <h3>Discussion</h3> We report the histologic, endoscopic, and symptomatic improvement in refractory pediatric EoE following treatment with monthly dupilumab in a ten-year-old male. Our findings suggest that the use of dupilumab can be extended to the pediatric population. Additionally, our case suggests that monthly injections, rather than the weekly injections utilized for adult EoE treatment, may be sufficient. Lastly, dupilumab also allowed for the liberalization of our patient's diet with sustained histologic and endoscopic resolution. In summary, dupilumab successfully treated refractory EoE and sustained disease remission despite allergen reintroduction.

Longitudinal analyses of CLL in mice identify leukemia-related clonal changes including a Myc gain predicting poor outcome in patients

Chronic lymphocytic leukemia (CLL) is a B-cell malignancy mainly occurring at an advanced age with no single major genetic driver. Transgenic expression of TCL1 in B cells leads after a long latency to a CLL-like disease in aged Eµ-TCL1 mice suggesting that TCL1 overexpression is not sufficient for full leukemic transformation. In search for secondary genetic events and to elucidate the clonal evolution of CLL, we performed whole exome and B-cell receptor sequencing of longitudinal leukemia samples of Eµ-TCL1 mice. We observed a B-cell receptor stereotypy, as described in patients, confirming that CLL is an antigen-driven disease. Deep sequencing showed that leukemia in Eµ-TCL1 mice is mostly monoclonal. Rare oligoclonality was associated with inability of tumors to develop disease upon adoptive transfer in mice. In addition, we identified clonal changes and a sequential acquisition of mutations with known relevance in CLL, which highlights the genetic similarities and therefore, suitability of the Eµ-TCL1 mouse model for progressive CLL. Among them, a recurrent gain of chromosome 15, where Myc is located, was identified in almost all tumors in Eµ-TCL1 mice. Interestingly, amplification of 8q24, the chromosomal region containing MYC in humans, was associated with worse outcome of patients with CLL.

Eosinophils in Eosinophilic Esophagitis: The Road to Fibrostenosis is Paved With Good Intentions.

Eosinophilic esophagitis (EoE) is an antigen-driven disease associated with epithelial barrier dysfunction and chronic type 2 inflammation. Eosinophils are the defining feature of EoE histopathology but relatively little is known about their role in disease onset and progression. Classically defined as destructive, end-stage effector cells, eosinophils (a resident leukocyte in most of the GI tract) are increasingly understood to play roles in local immunity, tissue homeostasis, remodeling, and repair. Indeed, asymptomatic esophageal eosinophilia is observed in IgE-mediated food allergy. Interestingly, EoE is a potential complication of oral immunotherapy (OIT) for food allergy. However, we recently found that patients with peanut allergy may have asymptomatic esophageal eosinophilia at baseline and that peanut OIT induces transient esophageal eosinophilia in most subjects. This is seemingly at odds with multiple studies which have shown that EoE disease severity correlates with tissue eosinophilia. Herein, we review the potential role of eosinophils in EoE at different stages of disease pathogenesis. Based on current literature we suggest the following: (1) eosinophils are recruited to the esophagus as a homeostatic response to epithelial barrier disruption; (2) eosinophils mediate barrier-protective activities including local antibody production, mucus production and epithelial turnover; and (3) when type 2 inflammation persists, eosinophils promote fibrosis.

Analysis of the Targets and Glycosylation of Monoclonal IgAs From MGUS and Myeloma Patients.

Previous studies showed that monoclonal immunoglobulins G (IgGs) of “monoclonal gammopathy of undetermined significance” (MGUS) and myeloma were hyposialylated, thus presumably pro-inflammatory, and for about half of patients, the target of the monoclonal IgG was either a virus—Epstein–Barr virus (EBV), other herpes viruses, hepatitis C virus (HCV)—or a glucolipid, lysoglucosylceramide (LGL1), suggesting antigen-driven disease in these patients. In the present study, we show that monoclonal IgAs share these characteristics. We collected 35 sera of patients with a monoclonal IgA (6 MGUS, 29 myeloma), and we were able to purify 25 of the 35 monoclonal IgAs (6 MGUS, 19 myeloma). Monoclonal IgAs from MGUS and myeloma patients were significantly less sialylated than IgAs from healthy volunteers. When purified monoclonal IgAs were tested against infectious pathogens and LGL1, five myeloma patients had a monoclonal IgA that specifically recognized viral proteins: the core protein of HCV in one case, EBV nuclear antigen 1 (EBNA-1) in four cases (21.1% of IgA myeloma). Monoclonal IgAs from three myeloma patients reacted against LGL1. In summary, monoclonal IgAs are hyposialylated and as described for IgG myeloma, significant subsets (8/19, or 42%) of patients with IgA myeloma may have viral or self (LGL1) antigen-driven disease.

Evaluation of long-term course in children with eosinophilic esophagitis reveals distinct histologic patterns and clinical characteristics

Eosinophilic esophagitis (EoE) is a chronic and increasingly prevalent antigen-driven disease. There is a paucity of information on long-term course in children. We sought to understand the longitudinal trajectory of pediatric EoE during routine clinical care. We prospectively enrolled children into an EoE database and reviewed their medical and pathologic records over 13years. From 2011 to 2015, 146 children with EoE seen for their first visit at our center had 2 or more years of follow-up and 3 or more endoscopies over an average follow-up period of 5.13years (range, 2-13years). Longitudinal eosinophilic inflammation during treatment demonstrated 3 patterns over time. Children with less than 15 eosinophils/high-power field (hpf) for greater than 75% of their follow-up period were termed continuous responders (CRs). Children with waxing and waning inflammation of less than 15 eosinophils/hpf for less than 75% but 25% or more of the follow-up period were termed intermittent responders (IRs). Nonresponders (NRs) were defined as having less than 15 eosinophils/hpf for less than 25% of their follow-up. Fifty-nine (40%) of 146 patients were CRs, 65 (45%) of 146 were IRs, and 22 (15%) of 146 were NRs. CRs differed from IRs and NRs on the parameter of male/female ratio (1:1 in CRs, 4:1 in IRs, and 6:1 in NRs; P<.001) and in their initial response to any therapy, including proton pump inhibitors (P<.001). Endoscopic severity correlated with esophageal eosinophilia (r=0.73, P<.001). On multivariate analysis, female sex and initial therapeutic response to medications or elimination diet were associated with long-term control of esophageal eosinophilia. Long-term pediatric EoE followed 3 different longitudinal trajectories of inflammation. The long-term histologic groups differed significantly in biological sex and initial therapeutic response.

Pediatric Eosinophilic Esophagitis Endotypes: Are We Closer to Predicting Treatment Response?

Eosinophilic esophagitis (EoE) is a chronic, food antigen-driven gastrointestinal disease that is characterized by esophageal eosinophilia. Currently, there are no Food and Drug Administration (FDA)-approved treatments for EoE, but the two most commonly prescribed therapies include topical corticosteroids and food elimination diets. Clinical trials have revealed a significant proportion of cases that are resistant to topical corticosteroids, and although we define EoE as a food antigen-driven disease, not all patients with EoE respond to elimination diets or even elemental diets. The varied response to treatments highlights the heterogeneity of EoE and the need for new treatment strategies. Despite the clinical differences in treatment response, predicting the outcome remains difficult since factors including age, histologic severity at diagnosis, atopic history, and anthropometrics are not predictive of treatment response. In our practice at an academic pediatric referral center, we observe distinct clinical EoE phenotypes, including cases with atopy, connective tissue disorders, or responsiveness to a proton pump inhibitor. Similar to the work in progress with asthma, stratification of patients with EoE by clinical phenotypes and/or molecular endotypes will likely assist with therapy selection and prediction of natural history. Molecular analysis with gene expression panels also shows promise in helping us classify patients based on molecular endotypes. In additional to the clinical and molecular classifications, more accurate histologic diagnostic criteria for EoE may help us tease out small differences between patient cohorts. Despite the leaps in knowledge over the past decade regarding EoE pathogenesis, it remains a challenge to predict the response to treatment. Future studies focused on molecular, genetic, and immunologic analyses of larger patient cohorts are needed to assist in identifying EoE phenotypes and endotypes as we attempt to improve patient outcomes in pediatric EoE.

Genetic variations in the TLR3 locus are associated with eosinophilic esophagitis.

Eosinophilic esophagitis (EoE) is an antigen-driven disease mediated by an abnormal immune Th2 response. The objective of this article is to investigate genes associated with regulating immune responses leading to disease susceptibility. Twenty-seven tag single nucleotide polymorphisms (tSNPs) selected in five candidate genes (TLR3, TLR4, FOXP3, FLG and TSLP) were genotyped in 218 EoE patients and 376 controls. Skin prick tests were carried out in EoE patients with a panel of 17 aeroallergens and 22 plant- and animal-derived foods. Five tSNPs located in the TSLP locus and one tSNP located in the TLR3 locus were significantly associated with EoE. The interactions between TLR3 and TSLP loci were analyzed. TLR3+/TSLP- and TLR3-/TSLP+ individuals showed a significantly reduced susceptibility to EoE compared to TLR3-/TSLP- individuals (OR = 0.66, p = 0.036 and OR = 0.23, p = 0.00014, respectively). Likewise, TLR3+/TSLP+ individuals showed the most decreased susceptibility of developing EoE (OR = 0.16, p = 0.0001). However, the interaction gain attributed to the combination of both genes was negative (IG = -4.52%), which indicated redundancy or independent effect. Additionally, TLR3 locus was found to be associated with aeroallergen and food sensitization in EoE patients (OR = 9.67, pc = 0.025 and OR = 0.53, pc = 0.048, respectively). TLR3 constitutes a novel genetic susceptibility locus for developing EoE, and the effects would be independent of TSLP.

Development of an Antigen-driven Colitis Model to Study Presentation of Antigens by Antigen Presenting Cells to T Cells.

Inflammatory bowel disease (IBD) is a chronic inflammation which affects the gastrointestinal tract (GIT). One of the best ways to study the immunological mechanisms involved during the disease is the T cell transfer model of colitis. In this model, immunodeficient mice (RAG(-/-) recipients) are reconstituted with naive CD4(+) T cells from healthy wild type hosts. This model allows examination of the earliest immunological events leading to disease and chronic inflammation, when the gut inflammation perpetuates but does not depend on a defined antigen. To study the potential role of antigen presenting cells (APCs) in the disease process, it is helpful to have an antigen-driven disease model, in which a defined commensal-derived antigen leads to colitis. An antigen driven-colitis model has hence been developed. In this model OT-II CD4(+) T cells, that can recognize only specific epitopes in the OVA protein, are transferred into RAG(-/-) hosts challenged with CFP-OVA-expressing E. coli. This model allows the examination of interactions between APCs and T cells in the lamina propria.

Mutations in the Fc-region of IgG from synovial fluids of patients with rheumatoid arthritis

AbstractRheumatoid arthritis an antigen-driven autoimmune disease and the eliciting antigens are unknown. They should be present in immune complexes of synovial fluids. The immune complexes were isolated from synovial fluids of patients with rheumatoid arthritis and analyzed by polyacrylamide gel electrophoresis and Western blotting. Immune complexes contained IgG as major protein. The antibodies dissociated at pH 2.5 and self-aggregated upon neutralization. In ELISA assays, they had the highest specificity to homologous IgG, less to normal IgG and lowest of heterologous arthritic IgG confirming earlier results that altered IgG structures were antigenic. Sequencing of the Fc-regions revealed mutations in all patients analyzed. Therefore, mutations within the Fc-regions of IgG could be antigens in rheumatoid arthritis. We propose that methods should be developed to prove this hypothesis.

Giant-Cell Arteritis: Immunopathogenic Mechanisms Involved in Vascular Inflammation and Remodeling

Giant-cell arteritis (GCA) is a large-vessel granulomatous vasculitis in which aging, gender and genetics likely play a significant role. The association with polymorphisms in the major histocompatibility complex suggests that GCA may be an antigen-driven disease. Immunopathology studies performed with temporal artery biopsies from patients with GCA have generated relevant clues regarding to pathogenesis by indicating participation of Th1 and Th17-mediated pathways, a prominent role for macrophages in tissue injury, and the relevance of vascular response to inflammation. Vascular wall elements, especially endothelial cells and vascular smooth muscle cells are not passive bystanders. Through expression of chemokines and adhesion molecules vascular cells contribute to the continuous recruitment of inflammatory cells that are able to enter the artery wall through newly formed neovessels. Inflammatory cell products, as well as vascular injury, trigger a vascular remodelling process. This eventually leads to the development of intimal hyperplasia and vascular lumen obliteration, source of ischemic complications.

Dietary and pharmacological aspects of eosinophilic esophagitis

Eosinophilic esophagitis is considered to be a chronic antigen-driven disease whereby food and/or aeroallergens induce a chronic inflammatory infiltrate in the esophagus leading to pathological hyperplasia of the epithelial and muscular layers, fibrosis of the lamina propria and symptoms of dysphagia and food impaction. Eosinophilic esophagitis is often associated with other allergic diseases such as asthma or atopic dermatitis. Current first line treatments of the disease include strict dietary modification and topical anti-inflammatory steroids. In this review the authors summarize currently available treatment strategies of eosinophilic esophagitis.

Eosinophilic esophagitis: a clinicopathological review.

Eosinophilic esophagitis (EoE) is considered to be a chronic antigen-driven disease whereby food and/or aeroallergens induce a chronic inflammatory infiltrate in the esophagus, resulting in pathological hyperplasia of the epithelia and muscular layers, and fibrosis of the lamina propria (referred to collectively as remodelling) and the symptoms of dysphagia and food impaction. EoE shares features with other atopic conditions of asthma and atopic dermatitis, such as a TH2 cytokine milieu and a mixed inflammatory infiltrate of eosinophils, mast cells and lymphocytes. Relatively distinct features include the strong male predominance amongst adult patients, and the expression of the eosinophil chemokine eotaxin 3. Current first line treatments such as strict dietary modification and corticosteroids fail many patients. Looking forward, clarification of distinct genotype/phenotype associations, determining the reversibility of remodelling following treatment, and the development of new pharmacotherapies that target fibrotic pathways (as opposed to eosinophilic inflammation per se) or specifically improve barrier integrity appear relevant.

SP0002 Pathogenic Mechanisms in Giant-Cell Arteritis

Giant-cell arteritis (GCA) is a chronic inflammatory disease of large vessels. The epidemiology of GCA suggests that genetic background play a role in pathogenesis. Several polymorphisms have been associated with...

Immunoglobulin G4-associated cholangitis: Dominating immunoglobulin G4-positive clones within the B-cell receptor repertoire indicate light at the end of a long tunnel

Immunoglobulin G4-associated cholangitis: Dominating immunoglobulin G4-positive clones within the B-cell receptor repertoire indicate light at the end of a long tunnel

The Nature of the Antigen Determines Leukemia Development and Behavior in the Eμ-TCL1 Transgenic Mouse Model of CLL

AbstractAbstract 181Studies conducted over the past decade have revealed a strong association between the mutational status of the immunoglobulin heavy-chain variable region (IGHV) genes and clinical course in patients with chronic lymphocytic leukemia (CLL). In patients with aggressive CLL, the leukemic cells typically express B cell receptors (BCRs) encoded by unmutated IGHV genes, whereas these genes are most often mutated in leukemic cells from patients with indolent disease. The mutational status of the IGHV genes reflects features of the antigen, such as antigen structure, form, presentation and affinity, indicating that the difference in the clinical course between IGHV-unmutated and IGHV-mutated CLL could be due to recognition of different types of antigens. In line with this possibility, recent studies have shown that IGHV-unmutated CLL (U-CLL) cells frequently express polyreactive BCRs that bind with low affinity to both microbial antigens and autoantigens translocated or exposed on apoptotic cells, whereas such reactivity is infrequent in IGHV-mutated CLL (M-CLL).To further explore the possibility that the clinical course in CLL is determined by the availability of particular types of antigenic stimuli, we investigated the impact of different antigen/BCR interactions on leukemia development and behavior in the Eμ-TCL1 transgenic mouse model of CLL. We initially established three cohorts of Eμ-TCL1 transgenic mice that expressed transgenic BCRs with different antigen specificity. Two of these cohorts expressed low-affinity unmutated transgenic BCRs reactive with the antigens phosphatidylcholine (PtC) and Sm (IgPtC and IgSm, respectively), whereas the third cohort expressed a high-affinity mutated transgenic BCR (IgHEL) specific for the antigen hen egg lysozyme (HEL). Of note, Sm is a ribonucleoprotein complex that is translocated to the surface of apoptotic cells and has been shown to be recognized by certain human U-CLL BCRs, whereas PtC is a cell membrane component that is exposed on senescent red blood cells and gut bacteria. Because no data are currently available regarding the reactivity of the M-CLL BCRs, we subdivided the cohort of Eμ-TCL1/IgHEL double transgenic mice into four additional cohorts. These included a cohort without antigen (Eμ-TCL1/IgHEL), a cohort in which HEL was provided as a foreign antigen (Eμ-TCL1/IgHEL double transgenic mice repetitively immunized with particles coated with HEL and CpG oligonucleotides), a cohort in which HEL was provided as a soluble autoantigen (Eμ-TCL1/IgHEL/sHEL triple transgenic mice) and a cohort in which HEL was provided as a membrane-bound autoantigen exposed on apoptotic cells (Eμ-TCL1/IgHEL/mHEL-KK triple transgenic mice). Each cohort consisted of 12–14 animals, of which at least 8 have been followed for >1 year.Animals from all cohorts developed CD5-positive B cell leukemias, but only in Eμ-TCL1/IgSm and Eμ-TCL1/IgPtC mice the leukemic cells expressed a transgenic BCR. In Eμ-TCL1/IgHEL mice the leukemias were always derived from the small percentage of B cells that express an endogenous BCR, whereas B cells that express the transgenic IgHEL BCR were never transformed. Interestingly, leukemia development and progression was more rapid in Eμ-TCL1/IgPtC than Eμ-TCL1/IgSm transgenic mice (7/14 at 6 months of age and 2/10 at 8 months of age, respectively). Since PtC is expressed as both a foreign- (gut flora) and self- (senescent red blood cells) antigen, we investigated whether suppression of gut flora will affect the growth of adoptively transferred Eμ-TCL1/IgPtC leukemias. Pretreatment of syngeneic recipient mice with a three-week course of broad-spectrum antibiotics significantly delayed leukemia growth, suggesting that PtC is more potent in driving the expansion of the leukemic clone when expressed as a foreign than self antigen.To summarize, these data demonstrate that U-CLL can be induced by both microbial antigens and autoantigens exposed on apoptotic cells, including autoantigens that are recognized by human CLL cells, such as Sm. In contrast, M-CLL can not be induced by chronic or repetitive antigen stimulation, regardless whether the antigen is provided as a foreign antigen, as a soluble autoantigen, or as a membrane-bound autoantigen exposed on apoptotic cells. Collectively, these data suggest that the mechanisms that drive U-CLL and M-CLL are different and indicate that only U-CLL is an antigen-driven disease. Disclosures:No relevant conflicts of interest to declare.

Eosinophilic gastrointestinal diseases—clinically diverse and histopathologically confounding

Eosinophilic gastrointestinal diseases are a group of chronic diseases characterized by a range of symptoms caused by eosinophilic inflammation of various parts of the gastrointestinal tract. Other causes for eosinophilia need to be ruled out prior to making the diagnosis of EGIDs. The most common form of EGID is eosinophilic esophagitis (EoE), an antigen-driven disease that afflicts children and adults and has been identified across the world. Histological features include dense eosinophilia of the esophageal mucosa, eosinophil degranulation, eosinophil microabscess formation, and other features of epithelial inflammation including basal zone hyperplasia and rete pege elongation. Treatments include dietary exclusions and topical corticosteroids.

HTLV-1 Epitope (BA21) Reactivity in Rare Bone Marrow Failure Diseases

AbstractAbstract 1724LGL leukemia is thought to be an antigen-driven disease. Extensive data support the antigen activated nature of leukemic LGL cells. Leukemic LGL constitutively express perforin and other markers of activated killer cells. T-LGL leukemia has been characterized as an accumulation of apoptosis resistant effector memory cytotoxic T lymphocytes (CTL). The actual target recognized by these activated CTL is still not characterized. LGL leukemia is at one end of a spectrum of hematologic disorders characterized by aberrant CTL responses. Conditions at the other end of this spectrum also feature CTL attacks on bone marrow, leading to cytopenia. These conditions are known as bone marrow failure (BMF) diseases and include pure red cell aplasia (PRCA), myelodysplastic syndromes (MDS), aplastic anemia (AA), and paroxysmal nocturnal hemoglobinuria (PNH). LGL leukemia is characterized by an easily detectable dominant clone whereas the CTL clones in these marrow failure diseases are less obvious. It has been postulated that exposure to infectious agents contributes to the onset of the full spectrum of LGL-driven diseases. One approach to determine exposure to infectious agents is to study the antibody patterns of infected and non-infected populations. In clinical screening, sera are usually assayed by ELISA to check for reactivity against recombinant viral proteins, followed by Western blot and PCR. In the case of human T cell leukemia viruses 1 and 2 (HTLV-1/2), less than 1% of the general U.S. population demonstrates cross-reactive antibodies. Conversely, at least 21% of LGL leukemia patients exhibit cross-reactive serology to HTLV1/2. The pattern of reactivity is very different between LGL leukemia patients and other cross-reactive groups. Comprehensive testing reveals that most LGL leukemia patients are not infected with HTLV-1/2, or with HTLV-3/4. We have demonstrated that HTLV Env reactivity in LGL leukemia was directed at the transmembrane-associated BA21 region/p21e. The BA21 epitope overlaps the immunogenic p21e region of the HTLV-1 envelope. Small scale studies indicated that at least 25% of sera from LGL leukemia patients were reactive to BA21, and that reactivity coincided with elevated overall HTLV-1 serum antibody expression. Since the presumptive antigen involved in the pathogenesis of LGL leukemia is not known, the identification of disease-specific antigens that are not cross-reactive with normal specimens is critical. To achieve this goal, a different way to look at epitope specificity is needed. We addressed this need by performing a B-cell epitope analysis for the BA21 sequence using multiple prediction databases. Antigenicity was predicted for three regions of BA21, namely the amino terminus containing EQCR, and two regions near the carboxyl terminus (PPLE, WGLN). Of these, PPLE-containing sequences were predicted to be the most immunogenic. We then used array-adapted alanine screening followed by ELISA to select disease-specific BA21 epitopes. Overall, 80 sequences were tested for specificity against alanine substitutions, using up to 10 mcL of serum per patient. The results of the array-adapted alanine screen clearly demonstrated that PPLE-containing sequences were universally recognized by LGL leukemia and normal serum groups. Conversely, peptides that included the amino terminus with sequence EQCR were better recognized against their alanine substituted sequences. ELISA testing was therefore performed for peptides from these regions. The resulting BA21 epitope was recognized by at least 40% of LGL leukemia sera but not by normal donor sera. Since a common pathogenesis is postulated for other CTL-mediated hematologic diseases, the levels of BMF-BA21 IgG were determined for participants in the Bone Marrow Failure Diseases Consortium of the Rare Diseases Clinical Research Network. We found that a substantial number of sera from participants with MDS, AA, PNH and PRCA also recognized the epitope. Reactivity with the BMF-BA21 epitope was independently associated with CTL-driven BMF diseases. These data provide further support for the hypothesis that a variety of hematologic diseases characterized by antigen-activated CTL result from a common pathogenetic mechanism. This project was supported by NIH Grant Number U54RR019397. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the NIH. Disclosures:No relevant conflicts of interest to declare.

Qu'a-t-on appris sur la maladie de Horton depuis dix ans ?

Introduction. – We propose a review on the current state of knowledge in giant cell arteritis (GCA), with particular emphasis on advances produced during the past 10 years. Current knowledge and key points. – The physiopathology of GCA is better understood. GCA is considered as a T-cell mediated, antigen driven disease. The expression of interferon- γ greatly influences the clinical expression of the vasculitis. The disease occurs preferentially in women. HLADR4 group and an atheromatous background have been shown to be risk factors for the disease. Infections (parainfluenzae virus, parvovirus B19) may act as triggers at the onset of GCA. In Europe, GCA incidence seems to be increasing in most countries in which it has been studied, especially in women. The diagnostic usefulness of the halo sign detected by high resolution Doppler ultrasonography seems limited. An excess of cardiovascular mortality is described in some countries. There is no consensus regarding the risk factors for thrombotic events. Randomized studies have not proved that methotrexate is a significantly efficient corticosteroid sparing agent. The value of high doses of methylprednisolone for severe thrombotic events has not been established. Benefits and risks of antiaggregation and anticoagulation are unknown. Perspectives. – Numerous important questions regarding the management of GCA remain unresolved. Well designed prospective studies are rare, and necessary in the future.

Giant cell arteritis. Epidemiology, etiology and pathogenesis.

Giant cell arteritis (GCA) is a chronic inflammatory disorder targeting large and medium-sized arteries, which predominantly affects postmenopausal women. Its high incidence in populations with Scandinavian lineage, some familial accumulation, and the association with the HLA-DR4 haplotype indicate a genetic predisposition. Epidemiological observations, as well as the symptomatology, may indicate an infectious origin, but so far GCA has not been shown to be a truly infectious form of vasculitis. Immunological research indicates an antigen-driven disease with local T-cell and macrophage activation in the vessel wall. Morphologically, the inflammatory process appears to be initiated by a foreign-body giant-cell attack on calcified internal elastic membrane in arteries and on calcified atrophic parts of the aortic media. The ensuing diffuse chronic inflammation leads to vessel dilatation and extensive intimal thickening. The latter, which relates to the production of promoting factors by the inflammatory cells, causes arterial stenosis and ischemic complications. The possible role of female sex hormones in GCA requires further investigation. Mononuclear and giant cells in GCA display the cytoplasmic accumulation of estrogen receptor (ER) alpha. Cytoplasmic ER-alpha is also seen in media smooth-muscle cells in GCA and in non-GCA controls, but nucleotide sequence analysis of the ER-alpha gene revealed no differences between GCA patients and controls. In the future, comprehensive morphological, cell biological and immunological research will be required for a better understanding of the complex etiology and pathogenesis of GCA.