Pathogenesis, immunology, and immune-targeted management of the multisystem inflammatory syndrome in children (MIS-C) or pediatric inflammatory multisystem syndrome (PIMS): EAACI Position Paper

Multisystem inflammatory syndrome in children (MIS-C) is a rare, but severe complication of coronavirus disease 2019 (COVID-19). It develops approximately 4 weeks after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and involves hyperinflammation with multisystem injury, commonly progressing to shock. The exact pathomechanism of MIS-C is not known, but immunological dysregulation leading to cytokine storm plays a central role. In response to the emergence of MIS-C, the European Academy of Allergy and Clinical Immunology (EAACI) established a task force (TF) within the Immunology Section in May 2021. With the use of an online Delphi process, TF formulated clinical statements regarding immunological background of MIS-C, diagnosis, treatment, follow-up, and the role of COVID-19 vaccinations. MIS-C case definition is broad, and diagnosis is made based on clinical presentation. The immunological mechanism leading to MIS-C is unclear and depends on activating multiple pathways leading to hyperinflammation. Current management of MIS-C relies on supportive care in combination with immunosuppressive and/or immunomodulatory agents. The most frequently used agents are systemic steroids and intravenous immunoglobulin. Despite good overall short-term outcome, MIS-C patients should be followed-up at regular intervals after discharge, focusing on cardiac disease, organ damage, and inflammatory activity. COVID-19 vaccination is a safe and effective measure to prevent MIS-C. In anticipation of further research, we propose a convenient and clinically practical algorithm for managing MIS-C developed by the Immunology Section of the EAACI.

The impact of type 2 immunity and allergic diseases in atherosclerosis

Allergic diseases are allergen-induced immunological disorders characterized by the development of type 2 immunity and IgE responses. The prevalence of allergic diseases has been on the rise alike cardiovascular disease (CVD), which affects arteries of different organs such as the heart, the kidney and the brain. The underlying cause of CVD is often atherosclerosis, a disease distinguished by endothelial dysfunction, fibrofatty material accumulation in the intima of the artery wall, smooth muscle cell proliferation, and Th1 inflammation. The opposed T-cell identity of allergy and atherosclerosis implies an atheroprotective role for Th2 cells by counteracting Th1 responses. Yet, the clinical association between allergic disease and CVD argues against it. Within, we review different phases of allergic pathology, basic immunological mechanisms of atherosclerosis and the clinical association between allergic diseases (particularly asthma, atopic dermatitis, allergic rhinitis and food allergy) and CVD. Then, we discuss putative atherogenic mechanisms of type 2 immunity and allergic inflammation including acute allergic reactions (IgE, IgG1, mast cells, macrophages and allergic mediators such as vasoactive components, growth factors and those derived from the complement, contact and coagulation systems) and late phase inflammation (Th2 cells, eosinophils, type 2 innate-like lymphoid cells, alarmins, IL-4, IL-5, IL-9, IL-13 and IL-17).

Protocol to desensitize human and murine mast cells after polyclonal IgE sensitization

In this protocol, we provide detailed instructions to desensitize human and murine mast cells (MCs) after polyclonal IgE sensitization. Moreover, we specify the steps for MC degranulation assessment after desensitization, measuring CD63 and CD107a expression by flow cytometry and β-hexosaminidase activity. Desensitized MCs can be used directly for co-culture with other cell types, immunofluorescence, live imaging, and omics approaches. For complete details on the use and execution of this protocol, please refer to López-Sanz et al. (2022).

Cigarette smoke augments CSF3 expression in neutrophils to compromise alveolar-capillary barrier function during influenza infection

BACKGROUND

Cigarette smokers are at increased risk of acquiring influenza, developing severe disease and requiring hospitalisation/intensive care unit admission following infection. However, immune mechanisms underlying this predisposition are incompletely understood, and therapeutic strategies for influenza are limited.

METHODS

We used a mouse model of concurrent cigarette smoke exposure and H1N1 influenza infection, colony-stimulating factor (CSF)3 supplementation/receptor (CSF3R) blockade and single-cell RNA sequencing (scRNAseq) to investigate this relationship.

RESULTS

Cigarette smoke exposure exacerbated features of viral pneumonia such as oedema, hypoxaemia and pulmonary neutrophilia. Smoke-exposed infected mice demonstrated an increase in viral (v)RNA, but not replication-competent viral particles, relative to infection-only controls. Interstitial rather than airspace neutrophilia positively predicted morbidity in smoke-exposed infected mice. Screening of pulmonary cytokines using a novel dysregulation score identified an exacerbated expression of CSF3 and interleukin-6 in the context of smoke exposure and influenza. Recombinant (r)CSF3 supplementation during influenza aggravated morbidity, hypothermia and oedema, while anti-CSF3R treatment of smoke-exposed infected mice improved alveolar-capillary barrier function. scRNAseq delineated a shift in the distribution of Csf3 + cells towards neutrophils in the context of cigarette smoke and influenza. However, although smoke-exposed lungs were enriched for infected, highly activated neutrophils, gene signatures of these cells largely reflected an exacerbated form of typical influenza with select unique regulatory features.

CONCLUSION

This work provides novel insight into the mechanisms by which cigarette smoke exacerbates influenza infection, unveiling potential therapeutic targets (e.g. excess vRNA accumulation, oedematous CSF3R signalling) for use in this context, and potential limitations for clinical rCSF3 therapy during viral infectious disease.

Mast Cell Desensitization in Allergen Immunotherapy

Allergen immunotherapy (AIT) is the only treatment with disease-transforming potential for allergic disorders. The immunological mechanisms associated with AIT can be divided along time in two phases: short-term, involving mast cell (MC) desensitization; and long-term, with a regulatory T cell (Treg) response with significant reduction of eosinophilia. This regulatory response is induced in about 70% of patients and lasts up to 3 years after AIT cessation. MC desensitization is characteristic of the initial phase of AIT and it is often related to its success. Yet, the molecular mechanisms involved in allergen-specific MC desensitization, or the connection between MC desensitization and the development of a Treg arm, are poorly understood. The major AIT challenges are its long duration, the development of allergic reactions during AIT, and the lack of efficacy in a considerable proportion of patients. Therefore, reaching a better understanding of the immunology of AIT will help to tackle these short-comings and, particularly, to predict responder-patients. In this regard, omics strategies are empowering the identification of predictive and follow-up biomarkers in AIT. Here, we review the immunological mechanisms underlying AIT with a focus on MC desensitization and AIT-induced adverse reactions. Also, we discuss the identification of novel biomarkers with predictive potential that could improve the rational use of AIT.

The cannabinoid WIN55212-2 impairs peanut allergic sensitization and promotes the generation of allergen-specific regulatory T cells

BACKGROUND

Cannabinoids are lipid-derived mediators with anti-inflammatory properties in different diseases. WIN55212-2, a non-selective synthetic cannabinoid, reduces immediate anaphylactic reactions in a mouse model of peanut allergy, but its capacity to prevent peanut allergic sensitization and the underlying mechanisms remains largely unknown.

OBJECTIVE

To investigate the capacity of WIN55212-2 to immunomodulate peanut-stimulated human dendritic cells (DCs) and peanut allergic sensitization in mice.

METHODS

Surface markers and cytokines were quantified by flow cytometry, ELISA and qPCR in human monocyte-derived DCs (hmoDCs) and T cell cocultures after stimulation with peanut alone or in the presence of WIN55212-2. Mice were epicutaneously sensitized with peanut alone or peanut/WIN55212-2. After peanut challenge, drop in body temperature, hematocrit, clinical symptoms, peanut-specific antibodies in serum and FOXP3⁺ regulatory (Treg) cells in spleen and lymph nodes were quantified. Splenocytes were stimulated in vitro with peanut to analyse allergen-specific T cell responses.

RESULTS

WIN55212-2 reduced peanut-induced hmoDC activation and promoted the generation of CD4⁺ CD127^- CD25⁺ FOXP3⁺ Treg cells, while reducing the induction of IL-5-producing T cells. In vivo, WIN55212-2 impaired the peanut-induced migration of DCs to lymph nodes and their maturation. WIN55212-2 significantly reduced the induction of peanut-specific IgE and IgG₁ antibodies in serum during epicutaneous peanut sensitization, reduced the clinical symptoms score upon peanut challenge and promoted the generation of allergen-specific FOXP3⁺ Treg cells.

CONCLUSIONS

The synthetic cannabinoid WIN55212-2 interferes with peanut sensitization and promotes tolerogenic responses, which might well pave the way for the development of novel prophylactic and therapeutic strategies for peanut allergy.

Oral Immunotherapy for Food-Allergic Children: A Pro-Con Debate

The prevalence of food allergy has increased in recent years, especially in children. Allergen avoidance, and drugs in case of an allergic reaction, remains the standard of care in food allergy. Nevertheless, increasing attention has been given to the possibility to treat food allergy, through immunotherapy, particularly oral immunotherapy (OIT). Several OIT protocols and clinical trials have been published. Most of them focus on children allergic to milk, egg, or peanut, although recent studies developed protocols for other foods, such as wheat and different nuts. OIT efficacy in randomized controlled trials is usually evaluated as the possibility for patients to achieve desensitization through the consumption of an increasing amount of a food allergen, while the issue of a possible long-term sustained unresponsiveness has not been completely addressed. Here, we evaluated current pediatric OIT knowledge, focusing on the results of clinical trials and current guidelines. Specifically, we wanted to highlight what is known in terms of OIT efficacy and effectiveness, safety, and impact on quality of life. For each aspect, we reported the pros and the cons, inferable from published literature. In conclusion, even though many protocols, reviews and meta-analysis have been published on this topic, pediatric OIT remains a controversial therapy and no definitive generalized conclusion may be drawn so far. It should be an option provided by specialized teams, when both patients and their families are prone to adhere to the proposed protocol. Efficacy, long-term effectiveness, possible role of adjuvant therapies, risk of severe reactions including anaphylaxis or eosinophilic esophagitis, and impact on the quality of life of both children and caregivers are all aspects that should be discussed before starting OIT. Future studies are needed to provide firm clinical and scientific evidence, which should also consider patient reported outcomes.

Memory Generation and Re-Activation in Food Allergy

Recent evidence has highlighted the critical role of memory cells in maintaining lifelong food allergies, thereby identifying these cells as therapeutic targets. IgG⁺ memory B cells replenish pools of IgE-secreting cells upon allergen exposure, which contract thereafter due to the short lifespan of tightly regulated IgE-expressing cells. Advances in the detection and highly dimensional analysis of allergen-specific B and T cells from allergic patients have provided insight on their phenotype and function. The newly identified Th2A and Tfh13 populations represent a leap in our understanding of allergen-specific T cell phenotypes, although how these populations contribute to IgE memory responses remains poorly understood. Within, we discuss the mechanisms by which memory B and T cells are activated, integrating knowledge from human systems and fundamental research. We then focus on memory reactivation, specifically, on the pathways of secondary IgE responses. Throughout, we identify areas of future research which will help identify immunotargets for a transformative therapy for food allergy.

Interrupting reactivation of immunologic memory diverts the allergic response and prevents anaphylaxis

BACKGROUND

IgE production against innocuous food antigens can result in anaphylaxis, a severe life-threatening consequence of allergic reactions. The maintenance of IgE immunity is primarily facilitated by IgG+ memory B cells, as IgE+ memory B cells and IgE+ plasma cells are extremely scarce and short-lived, respectively.

OBJECTIVE

Our aim was to investigate the critical requirements for an IgE recall response in peanut allergy.

METHODS

We used a novel human PBMC culture platform, a mouse model of peanut allergy, and various experimental readouts to assess the IgE recall response in the presence and absence of IL-4Rα blockade.

RESULTS

In human PBMCs, we have demonstrated that blockade of IL-4/IL-13 signaling aborted IgE production after activation of a recall response and skewed the cytokine response away from a dominant type 2 signature. TH2A cells, identified by single-cell RNA sequencing, expanded with peanut stimulation and maintained their pathogenic phenotype in spite of IL-4Rα blockade. In mice with allergy, anti-IL-4Rα provided long-lasting suppression of the IgE recall response beyond antibody treatment and fully protected against anaphylaxis.

CONCLUSION

The findings reported here advance our understanding of events mediating the regeneration of IgE in food allergy.

B Cell Development and T-Dependent Antibody Response Are Regulated by p38γ and p38δ

p38MAP kinase (MAPK) signal transduction pathways are important regulators of inflammation and the immune response; their involvement in immune cell development and function is still largely unknown. Here we analysed the role of the p38 MAPK isoforms p38γ and p38δ in B cell differentiation in bone marrow (BM) and spleen, using mice lacking p38γ and p38δ, or conditional knockout mice that lack both p38γ and p38δ specifically in the B cell compartment. We found that the B cell differentiation programme in the BM was not affected in p38γ/δ-deficient mice. Moreover, these mice had reduced numbers of peripheral B cells as well as altered marginal zone B cell differentiation in the spleen. Expression of co-stimulatory proteins and activation markers in p38γ/δ-deficient B cells are diminished in response to B cell receptor (BCR) and CD40 stimulation; p38γ and p38δ were necessary for B cell proliferation induced by BCR and CD40 but not by TLR4 signaling. Furthermore, p38γ/δ-null mice produced significantly lower antibody responses to T-dependent antigens. Our results identify unreported functions for p38γ and p38δ in B cells and in the T-dependent humoral response; and show that the combined activity of these kinases is needed for peripheral B cell differentiation and function.

Microbial Regulation of Enteric Eosinophils and Its Impact on Tissue Remodeling and Th2 Immunity

Eosinophils have emerged as multifaceted cells that contribute to tissue homeostasis. However, the impact of the microbiota on their frequency and function at mucosal sites remains unclear. Here, we investigated the role of the microbiota in the regulation of enteric eosinophils. We found that small intestinal (SI) eosinophilia was significantly greater in germ-free (GF) mice compared to specific pathogen free (SPF) controls. This was associated with changes in the production of enteric signals that regulate eosinophil attraction and survival, and was fully reversed by complex colonization. Additionally, SI eosinophils of GF mice exhibited more cytoplasmic protrusions and less granule content than SPF controls. Lastly, we generated a novel strain of eosinophil-deficient GF mice. These mice displayed intestinal fibrosis and were less prone to allergic sensitization as compared to GF controls. Overall, our study demonstrates that commensal microbes regulate intestinal eosinophil frequency and function, which impacts tissue repair and allergic sensitization to food antigens. These data support a critical interplay between the commensal microbiota and intestinal eosinophils in shaping homeostatic, innate, and adaptive immune processes in health and disease.

IL-17 Production by γδ+ T Cells Is Critical for Inducing Th17 Responses in the Female Genital Tract and Regulated by Estradiol and Microbiota

IL-17 can be produced by adaptive immune cells such as T_h17 cells and by immune cells that produce IL-17 without prior priming. This latter category, which we will refer to as "innate," includes innate cells such as NK cells and innate lymphoid cells and innate-like T cell populations such as NKT cells and γδ⁺ T cells. Studies in mucosal tissues have shown that the induction of T_h17 immunity is amplified by innate IL-17 produced within those tissues. However, the role of innate IL-17 and its effect on T_h17 induction in the female genital tract (FGT) is largely unknown. In this study, we characterize the primary source of IL-17-secreting vaginal cells and show that innate IL-17 plays a critical role in priming adaptive T_h17 responses in the FGT. Under homeostatic conditions, γδ⁺ T cells were the predominant source of innate IL-17 in the murine FGT, and this population was modulated by both the sex hormone estradiol and the presence of commensal microbiota. Compared with wild-type C57BL/6 mice, vaginal APCs isolated from IL-17A-deficient (IL-17A^-/- ) mice were severely impaired at priming T_h17 responses in APC-T cell cocultures. Furthermore, the defect in T_h17 induction in the absence of innate IL-17 was associated with impairment of IL-1β production by vaginal CD11c⁺ dendritic cells. Overall, our study describes a novel role for IL-17 in the FGT and further demonstrates the importance of factors in the vaginal microenvironment that can influence adaptive immune responses.

Is hybrid-PBL advancing teaching in biomedicine? A systematic review

BACKGROUND

The impact of instructional guidance on learning outcomes in higher biomedical education is subject of intense debate. There is the teacher-centered or traditional way of teaching (TT) and, on the other side, the notion that students learn best under minimal guidance such as problem-based learning (PBL). Although the benefits of PBL are well-known, there are aspects susceptible to improvement. Hence, a format merging TT and PBL (hybrid-PBL, h-PBL) may advance education in biomedical sciences.

METHODS

Studies that employed h-PBL in higher biomedical education compared to TT and/or pure PBL were systematically reviewed. Specifically, this review addressed the following question: does h-PBL in biomedical sciences result in superior marks and a better student's perception of the teaching and learning process?

RESULTS

We found that the use of h-PBL in higher biomedical sciences was superior compared to TT and pure-PBL. This was evidenced by the higher performance of the students in h-PBL as well as the level of student's satisfaction as compared to TT or pure PBL.

CONCLUSIONS

These findings encourage more research on investigating the pedagogical benefits of h-PBL. In addition, these data support an eclectic system in which the pedagogical tools from TT and PBL are used cooperatively in the best interest of the education and satisfaction of the students.

Kaiso-induced intestinal inflammation is preceded by diminished E-cadherin expression and intestinal integrity

Chronic intestinal inflammation contributes to pathologies such as inflammatory bowel disease (IBD) and colon cancer. While the precise etiology remains controversial, IBD is believed to manifest as a result of various factors. We previously reported that intestinal-specific overexpression of the transcription factor Kaiso results in an intestinal inflammatory response; however, the cause of this inflammation is unknown. To elucidate the underlying mechanism(s) of the Kaiso-mediated intestinal inflammatory phenotype, we evaluated two independent transgenic mouse lines that express varying levels of Kaiso (Kaiso^Tg). Histological analyses of Kaiso^Tg mice revealed intestinal damage including thickening of the mucosa, intestinal “lesions” and crypt abscesses, which are reminiscent of IBD pathology. Additionally, higher Kaiso levels induced intestinal neutrophilia as early as 12 weeks, which worsened as the mice aged. Notably, the Kaiso-induced intestinal inflammation correlated with a leaky intestinal barrier and mis-regulation of E-cadherin expression and localization. Interestingly, Kaiso overexpression resulted in reduced proliferation but enhanced migration of intestinal epithelial cells prior to the onset of inflammation. Collectively, these data suggest that Kaiso plays a role in regulating intestinal epithelial cell integrity and function, dysregulation of which contributes to a chronic inflammatory phenotype as mice age.

The Multifaceted B Cell Response in Allergen Immunotherapy

While allergen immunotherapy (AIT) for IgE-mediated diseases holds curative potential, the considerable heterogeneity in clinical outcomes may relate to the complex mechanisms of tolerance. The regulation of humoral immunity by AIT contributes to the suppression of allergic responses. Recent findings have revealed novel roles for IgA and IgG antibodies in the induction of tolerance. These mechanisms synergize with their ability to block allergen-IgE binding and mediate inhibitory signaling of effector cells of the allergic response. In addition, the regulatory activity of B cells in AIT extends beyond IL-10 secretion and induction of IgG₄. Here, we review the evolution of the B cell response during AIT with special emphasis on the novel protective mechanisms entailing humoral immunity.

Lifelong memory responses perpetuate humoral TH2 immunity and anaphylaxis in food allergy

BACKGROUND

A number of food allergies (eg, fish, shellfish, and nuts) are lifelong, without any disease-transforming therapies, and unclear in their underlying immunology. Clinical manifestations of food allergy are largely mediated by IgE. Although persistent IgE titers have been attributed conventionally to long-lived IgE⁺ plasma cells (PCs), this has not been directly and comprehensively tested.

OBJECTIVE

We sought to evaluate mechanisms underlying persistent IgE and allergic responses to food allergens.

METHODS

We used a model of peanut allergy and anaphylaxis, various knockout mice, adoptive transfer experiments, and in vitro assays to identify mechanisms underlying persistent IgE humoral immunity over almost the entire lifespan of the mouse (18-20 months).

RESULTS

Contrary to conventional paradigms, our data show that clinically relevant lifelong IgE titers are not sustained by long-lived IgE⁺ PCs. Instead, lifelong reactivity is conferred by allergen-specific long-lived memory B cells that replenish the IgE⁺ PC compartment. B-cell reactivation requires allergen re-exposure and IL-4 production by CD4 T cells. We define the half-lives of antigen-specific germinal centers (23.3 days), IgE⁺ and IgG₁⁺ PCs (60 and 234.4 days, respectively), and clinically relevant cell-bound IgE (67.3 days).

CONCLUSIONS

These findings can explain lifelong food allergies observed in human subjects as the consequence of allergen exposures that recurrently activate memory B cells and identify these as a therapeutic target with disease-transforming potential.

Estradiol Enhances CD4+ T-Cell Anti-Viral Immunity by Priming Vaginal DCs to Induce Th17 Responses via an IL-1-Dependent Pathway

Clinical and experimental studies have shown that estradiol (E2) confers protection against HIV and other sexually transmitted infections. Here, we investigated the underlying mechanism. Better protection in E2-treated mice, immunized against genital HSV-2, coincided with earlier recruitment and higher proportions of T_h1 and T_h17 effector cells in the vagina post-challenge, compared to placebo-treated controls. Vaginal APCs isolated from E2-treated mice induced 10-fold higher T_h17 and T_h1 responses, compared to APCs from progesterone-treated, placebo-treated, and estradiol-receptor knockout mice in APC-T cell co-cultures. CD11c⁺ DCs in the vagina were the predominant APC population responsible for priming these T_h17 responses, and a potent source of IL-6 and IL-1β, important factors for T_h17 differentiation. T_h17 responses were abrogated in APC-T cell co-cultures containing IL-1β KO, but not IL-6 KO vaginal DCs, showing that IL-1β is a critical factor for T_h17 induction in the genital tract. E2 treatment in vivo directly induced high expression of IL-1β in vaginal DCs, and addition of IL-1β restored T_h17 induction by IL-1β KO APCs in co-cultures. Finally, we examined the role of IL-17 in anti-HSV-2 memory T cell responses. IL-17 KO mice were more susceptible to intravaginal HSV-2 challenge, compared to WT controls, and vaginal DCs from these mice were defective at priming efficient T_h1 responses in vitro, indicating that IL-17 is important for the generation of efficient anti-viral memory responses. We conclude that the genital mucosa has a unique microenvironment whereby E2 enhances CD4⁺ T cell anti-viral immunity by priming vaginal DCs to induce T_h17 responses through an IL-1-dependent pathway.

Female sex hormones can affect susceptibility and immune responses to infections. While a number of previous studies, including our own, have shown that progesterone and progesterone-derived hormonal contraceptives increase susceptibility and impair immune responses, estradiol protects against sexually transmitted infections. The reason why estradiol is protective remains unknown. In this study, we investigated the effect of estradiol on dendritic cells, specialized immune cells that determine what type of anti-viral cellular immune responses will be mounted following infection with a sexually transmitted virus, HSV-2. Our studies show that estradiol influences dendritic cells in the vaginal tract of mice to initiate unique anti-viral T cell immunity that results in better protection against genital HSV-2 infection. This type of T cell response is unique to the vaginal tract and not found in any other mucosal lining of the body. This is the first study to show directly that estradiol, a female sex hormone, can determine how well the immune system will combat a sexually transmitted viral infection. The information from this study will be very important in understanding what type of immunity can protect women from sexually transmitted infections and how we can use this information to develop better vaccines.

Immunomodulatory effects of heated ovomucoid-depleted egg white in a BALB/c mouse model of egg allergy

Oral immunotherapy (OIT) is a promising therapeutic approach for treating food allergy. The treatment with heated ovomucoid-depleted egg white (HOMEW) in egg-allergic patients is noteworthy; however, OIT protocols are still experimental, and a better knowledge of the underlying mechanism is required. The objective of this work was to investigate the immunomodulatory effects of HOMEW and characterize the underlying mechanism in a BALB/c mouse model of egg allergy. Mice were sensitized with EW and treated with HOMEW. Post treatment, mice were challenged with EW and euthanized for collecting blood and spleen. Markers of allergic clinical outcomes were measured as histamine concentration, serum antibody activity, and cytokine production from cultured splenocytes. Digestibility of HOMEW was assessed mimicking physiological conditions in vitro. The HOMEW demonstrated high digestibility. The treatment induced a marked increase of the Th1/Th2 ratio in the high-dose treatment group. Treated mice had significantly less histamine, EW-specific IgE, and IL-4 and more IFN-γ and IL-10. This study confirms the mechanisms involved in successful tolerance induction with OIT using HOMEW and allows understanding of the vital role of surrogate allergy markers involved in immune modulation.

Human immunoglobulin E (IgE) binding to heated and glycated ovalbumin and ovomucoid before and after in vitro digestion

This study focuses on the effect of heating and Maillard reaction (MR) on the in vitro digestibility and rabbit IgG- and human IgE-binding properties of ovalbumin (OVA) and ovomucoid (OM) to estimate the impact of processing on their allergenicity. With the human sera studied, heat treatment significantly reduced IgE binding to both OVA and OM, whereas MR reduced the IgE binding to OVA but increased IgE binding to OM. In contrast, heat treatment significantly favored OVA digestibility but glycation impaired it, and these treatments did not affect the digestibility of OM. The changes observed in the digestibility affected the immunogenicity of the digests accordingly, so that the higher the digestibility, the lower the antibody binding. Heat treatment and glycation by MR showed an influence on the potential allergenicity of the main egg white proteins that could be related to their resistance to denaturation and digestive enzymes.