Characterization of IgE on human effector cells
Translated title
Karakterisering af IgE på humane effektor celler
Authors
Salzer, Madeleine Emilie ; Quach, Marlene
Term
4. term
Publication year
2020
Submitted on
2020-05-28
Abstract
Allergiske sygdomme er steget markant de seneste årtier og belaster både livskvalitet og samfundsøkonomi. Mange diagnoser bygger på måling af specifik IgE (sIgE), et antistof der viser, at en person er sensibiliseret. Men sIgE forudsiger ikke altid, om man får symptomer, og derfor er der brug for mere præcise, sikre tests. I denne sammenhæng undersøgte vi laboratorietests, der aktiverer de celler, som udløser allergiske reaktioner: mastceller og basofile. Formål: (1) At undersøge om mastceller fra personer med svær allergisk astma reagerer anderledes end mastceller fra raske, afhængigt af hvor stærkt IgE-antistoffer binder til allergenet (affinitet), og om dette påvirker senere mediatorfrigivelse. (2) At vurdere om mastcelle-aktiveringstest (MAT) og basofil-aktiveringstest (BAT) kan skelne mellem høj- og lavresponderende patienter til sublingual immunterapi (SLIT). Metoder: Vi dyrkede humane mastceller fra blodforstadier fra enten svære astmatikere eller raske kontroller og målte aktivering ved overflademarkøren CD63 med flowcytometri. Vi testede forskellige husstøvmide-specifikke IgE-varianter med forskellig bindingsstyrke (affinitet). Derudover sensibiliserede vi mastceller med serum/plasma fra birkepollenallergikere og med præ-behandlingsprøver fra en klinisk AIT-undersøgelse (GT-08). Både mastceller og fuldblods basofile blev aktiveret med en SLIT-tablet, og CD63-opregulering blev målt. Resultater: Vi fandt ingen klar forskel mellem patient- og kontrolgrupper i samlet mastcellereaktivitet eller følsomhed på tværs af IgE-affiniteter. Dog reagerede patientafledte mastceller i gennemsnit stærkere end kontrollernes, når de var sensibiliseret med lav-affinitets IgE. Baseline-reaktivitet og følsomhed matchede ikke kliniske samlet-scorer i GT-08-studiet. Hos birkepollenallergikere korrelerede baseline-reaktivitet med følsomhed, men ingen af delene forudsagde behandlingseffekt. MAT og BAT var kun svagt sammenlignelige, men MAT var reproducerbar med under 10 % variation i CD63 og stabile følsomhedsestimater. Konklusion: Mastceller viste affinitetsafhængig følsomhed inden for grupper, men vi fandt ingen tydelige forskelle mellem svære astmatikere og raske. Lav-affinitets IgE kan antyde, at astmatiske mastceller reagerer kraftigere på svagere stimuli, men dette kræver mere forskning. MAT udført på hvide blodcellefraktioner sensibiliseret med serum eller plasma var reproducerbar. Præ-behandlingstest af mastceller forudsagde ikke, hvem der får gavn af allergenimmunterapi, og BAT’s værdi som prædiktiv biomarkør er fortsat uafklaret.
Allergic diseases have risen sharply over recent decades, reducing quality of life and increasing societal costs. Diagnosis often relies on measuring specific IgE (sIgE), an antibody that indicates sensitization, but sIgE does not always predict who will develop symptoms. Safer, more accurate tests are therefore needed. This project examined laboratory tests that activate the cells driving allergic reactions: mast cells and basophils. Aims: (1) To test whether mast cells from people with severe allergic asthma respond differently from those of healthy controls depending on how strongly IgE antibodies bind to allergens (affinity), and whether this affects later mediator release. (2) To assess whether the mast cell activation test (MAT) and basophil activation test (BAT) can distinguish high from low responders to sublingual immunotherapy (SLIT). Methods: We grew human mast cells from blood progenitor cells from either severe asthmatics or healthy controls and measured activation by the surface marker CD63 using flow cytometry. We tested different house dust mite–specific IgE variants with different binding strengths (affinities). We also sensitized mast cells with serum/plasma from birch pollen–allergic individuals and with pre-treatment samples from a clinical allergen immunotherapy (AIT) study (GT-08). Both mast cells and whole-blood basophils were activated with a SLIT tablet, and CD63 upregulation was measured. Results: There was no clear difference between patient and control groups in overall mast cell reactivity or sensitivity across IgE affinities. However, when sensitized with low-affinity IgE, patient-derived mast cells showed higher average reactivity than controls. Baseline reactivity and sensitivity did not align with global clinical evaluation scores in the GT-08 study. Among birch-allergic individuals, baseline reactivity correlated with sensitivity, but neither measure predicted treatment effect. MAT and BAT showed low comparability and poor correlation, but MAT results were reproducible, with less than 10% variation in CD63 and consistent sensitivity estimates. Conclusion: Mast cells exhibited affinity-dependent sensitivity within groups, but no clear differences were found between severe asthmatics and healthy controls. Low-affinity IgE may hint that asthmatic mast cells respond more strongly to weaker stimuli, but this requires further study. MAT performed on white blood cell fractions sensitized with serum or plasma was reproducible. Pre-treatment mast cell testing did not predict who will benefit from allergen immunotherapy, and the predictive value of BAT remains inconclusive.
[This abstract was generated with the help of AI]
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