Immunoglobulin E and G autoantibodies against eosinophil proteins in children and adults with asthma and healthy subjects.

Background: Autoimmune IgG response has been described in the pathogenesis of asthma in adults, but IgE autoimmunity has been little explored. Considering high levels of blood eosinophils and immunoglobulin E in asthmatic patients, the possibility of IgE autoantibody response to eosinophil proteins arises. Objective: To explore the presence of IgE and IgG autoantibodies against Eosinophil peroxidase (EPX) and Eosinophil cationic protein (ECP). Methods: Three steps were followed: 1) The frequency of IgE and IgG autoantibodies against EPX and ECP was investigated among asthmatic and healthy subjects. 2) The ability of IgE autoantibodies to induce an inflammatory response (basophil activation) was performed. 3) The capacity of autoantibodies to identify patients with severe asthma was evaluated. Results: Asthmatic and healthy subjects had IgE and IgG autoantibodies against EPX and ECP. Anti-EPX IgE was significantly higher in asthmatic patients. Severe asthmatic patients had a higher frequency and higher levels of IgE and IgG autoantibodies compared to healthy subjects. There was not a correlation between autoantibodies and blood eosinophils. Children younger than 14 years of age had IgE and IgG autoantibodies against to EPX and ECP. IgE autoantibodies to EPX and ECP induced basophil activation in asthmatic patients. Conclusion: In this study, we identify for the first time IgE autoantibodies against EPX and ECP in adults and children patients with asthma; IgE and IgG autoantibodies against EPX and ECP could serve as a predictive biomarker of the clinical severity.

A Germline-Encoded Structural Arginine Trap Underlies the Anti-DNA Reactivity of a Murine V Gene Segment.

Autoimmunity may have its origins of early repertoire selection in developmental B cells. Such a primary repertoire is probably shaped by selecting B cells that can efficiently perform productive signaling, stimulated by self-antigens in the bone marrow, such as DNA. In support of that idea, we previously found a V segment from VH10 family that can form antibodies that bind to DNA independent of CDR3 usage. In this paper we designed four antibody fragments in a novel single-chain pre-BCR (scpre-BCR) format containing germinal V gene segments from families known to bind DNA (VH10) or not (VH4) connected to a murine surrogate light chain (SLC), lacking the highly charged unique region (UR), by a hydrophilic peptide linker. We also tested the influence of CDR2 on DNA reactivity by shuffling the CDR2 loop. The scpre-BCRs were expressed in bacteria. VH10 bearing scpre-BCR could bind DNA, while scpre-BCR carrying the VH4 segment did not. The CDR2 loop shuffling hampered VH10 reactivity while displaying a gain-of-function in the nonbinding VH4 germline. We modeled the binding sites demonstrating the conservation of a positivity charged pocket in the VH10 CDR2 as the possible cross-reactive structural element. We presented evidence of DNA reactivity hardwired in a V gene, suggesting a structural mechanism for innate autoreactivity. Therefore, while autoreactivity to DNA can lead to autoimmunity, efficiently signaling for B cell development is likely a trade-off mechanism leading to the selection of potentially autoreactive repertoires.

Antinuclear antibody prevalence in a general pediatric cohort from Mexico City: discordance between immunofluorescence and multiplex assays.

OBJECTIVE: To characterize antinuclear antibody (ANA) prevalence according to distinct assay methodologies in a pediatric cohort from Mexico City, and to further examine associations with age and sex. METHODS: Serum ANA were measured by indirect immunofluorescence assay (IFA) and multiplex immunoassay in 114 children aged 9-17 years. IFA was considered positive at a cutoff titer of ≥1:80. Agreement between assay methods was assessed by kappa statistic. Sensitivity, specificity, and 95% confidence intervals (CIs) of the multiplex were computed with IFA as the reference standard. RESULTS: Of the 114 children (mean age 14.7 [standard deviation 2.1] years; 54 [47%] female), 18 of 114 (15.8%) were ANA positive by IFA, and 11 of 114 (9.6%) by 11-antigen multiplex assay. ANA prevalence was higher in females compared with males by both of the methods (ratios 1.6-1.9 to 1). Agreement between tests was classified as slight by kappa (κ=0.177 [95% CI -0.051, 0.406]). The multiplex immunoassay had sensitivity of 22.2% (95% CI 6.4, 47.6) and specificity of 92.7% (95% CI 85.6, 97.0), and failed to capture 3 of 4 (75%) of the high-titer (≥1:1280) IFA-positives. CONCLUSION: Up to 15% of children in this general population cohort were ANA positive, with a higher rate of positivity among females according to both assay methods. Substantial discordance in ANA results was found between IFA and multiplex methods, even for high-titer IFA positives. These findings underscore the need to sufficiently account for assay characteristics when interpreting ANA test results, and support IFA as the more appropriate assay for studies of subclinical autoimmunity.

Tolerancia inmunológica, un recorrido en el tiempo: cómo discriminar entre lo propio y lo extraño / Immune tolerance, a walk through time: How does the immune system differentiate between self and foreign

Resumen Desde los primeros estudios en inmunología, ha sido evidente la necesidad de entender cómo, en condiciones normales, el sistema inmune tolera los antígenos propios y ataca algunos antígenos extraños que percibe como potencialmente peligrosos, y cómo, bajo ciertas circunstancias, la pérdida de la tolerancia desencadena enfermedades autoinmunes. Ha pasado más de medio siglo desde que Billingham, Medawar y Brent demostraron en un modelo experimental algunos eventos involucrados en el desarrollo de la tolerancia inmunológica. Desde entonces, los inmunólogos de trasplante han centrado sus esfuerzos en dilucidar los mecanismos que conllevan al mantenimiento de la tolerancia, con la esperanza de eludir las complicaciones de la inmunosupresión no específica y conseguir la prevención del rechazo crónico. Medawar (1953) argumentaba que durante el trasplante el sistema inmune del individuo se hacía tolerante al tejido trasplantado, manteniéndose la respuesta a otros antígenos. Estudios recientes han demostrado que la pérdida de la tolerancia al trasplante está asociada con una hiperrespuesta a los antígenos del tejido trasplantado, hecho que ha atormentado a los inmunólogos clínicos, quienes han encaminado sus esfuerzos a desarrollar sistemas de medición precisos que les permita evaluar qué tan tolerante podría ser un individuo al trasplante. Los intentos por inducir tolerancia en el individuo, se basan en la comprensión de los mecanismos básicos de tolerancia, cuyo conocimiento se ha desarrollado paralelamente con una mejor apreciación de la complejidad de la tolerancia inmune. En particular, se ha avanzado mucho en la comprensión del papel esencial de las células dendríticas tolerogénicas (CDT) y del mantenimiento de la tolerancia por células T reguladoras.

Abstract Since the first studies in immunology, there has been a clear need to understand how, under normal conditions, the immune system tolerates its own antigens and attacks some foreign antigens that it perceives as potentially dangerous and how, in certain circumstances, the loss of tolerance triggers autoimmune diseases. It has been over half a century since Billingham, Brent and Medawar demonstrated, in an experimental model, the mechanisms involved in the development of immunological tolerance. Since then transplant immunologists have intensively investigated the mechanisms involved in maintaining tolerance, in the hope of avoiding the complications of non-specific immunosuppression, as well as the prevention of chronic rejection. An important characteristic was observed by Medawar, who argued that during transplantation an individual's immune system is tolerant to transplanted tissue, maintaining the response to other antigens. Recent studies have shown that loss of tolerance to transplantation is associated with a hyper-response to antigens of the transplanted tissue; a problem that has plagued clinical immunologists, who have focused their efforts on developing accurate measurement systems to enable them to measure how an individual could be tolerant to transplant. Attempts to induce tolerance in the individual are based on understanding the basic mechanisms of tolerance, in which there has been significant progress. This growth in knowledge has been in parallel with a better appreciation of the complexity of immune tolerance. In particular, progress has been made in understanding the essential role of tolerogenic dendritic cells (CDS) and the maintenance of tolerance by regulatory T cells.