The immunoglobulin E receptor: expression and regulation

Neuronal FcεRIα directly mediates ocular itch via IgE-immune complex in a mouse model of allergic conjunctivitis

Background

Classical understanding of allergic conjunctivitis (ACJ) suggests that ocular itch results from a mast cell-dependent inflammatory process. However, treatments that target inflammatory mediators or immune cells are often unsatisfying in relieving the stubborn itch symptom. This suggests that additional mechanisms are responsible for ocular itch in ACJ. In this study, we aim to determine the role of neuronal FcεRIa in allergic ocular itch.

Methods

Calcium imaging was applied to observe the effect of IgE-immune complex in trigeminal neurons. Genomic FcεRIa knockout mice and adeno-associated virus (AAV) mediated sensory neuron FcεRIa knockdown mice were used in conjunction with behavioral tests to determine ocular itch. In addition, immunohistochemistry, Western blot and quantitative RT-PCR were used for in vitro experiments.

Results

We found that FcεRIα was expressed in a subpopulation of conjunctiva sensory neurons. IgE-IC directly activated trigeminal neurons and evoked acute ocular itch without detectible conjunctival inflammation. These effects were attenuated in both a global FcεRIa-knockout mice and after sensory neuronal-specific FcεRIa-knockdown in the mouse trigeminal ganglion. In an ovalbumin (OVA) induced murine ACJ model, FcεRIα was found upregulated in conjunctiva-innervating CGRP+ sensory neurons. Sensory neuronal-specific knockdown of FcεRIa significantly alleviated ocular itch in the ACJ mice without affecting the immune cell infiltration and mast cell activation in conjunctiva. Although FcεRIα mRNA expression was not increased by IgE in dissociated trigeminal ganglion neurons, FcεRIα protein level was enhanced by IgE in a cycloheximide-resistance manner, with concordant enhancement of neuronal responses to IgE-IC. In addition, incremental sensitization gradually enhanced the expression of FcεRIα in small-sized trigeminal neurons and aggravated OVA induced ocular itch.

Conclusions

Our study demonstrates that FcεRIα in pruriceptive neurons directly mediates IgE-IC evoked itch and plays an important role in ocular itch in a mouse model of ACJ. These findings reveal another axis of neuroimmune interaction in allergic itch condition independent to the classical IgE-mast cell pathway, and might suggest novel therapeutic strategies for the treatment of pruritus in ACJ and other immune-related disorders.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02417-x.

Association between Serum Immnunoglobulin E and Pterygium: A Population-Based Study from South Korea

PURPOSE

Several studies have shown that pterygium is associated with inflammation, angiogenesis, and fibrosis. However, it should be acknowledged that not enough is known about the association between immunoglobulin E (IgE) and pterygium. The present study was conducted to test the hypothesis that elevated serum IgE is associated with a greater prevalence of pterygium.

MATERIAL AND METHODS

A cross-sectional study was performed using data of 1,548 participants aged 30 years or older who were enrolled in the Korea National Health and Nutrition Examination Survey conducted in 2010. Multivariable logistic regression analysis was used to examine the relationship between pterygium and allergic conditions, including total serum IgE and allergen-specific serum IgE levels, after adjusting for potential confounding factors.

RESULTS

Participants with pterygium were more likely have increased IgE level (p = 0.009). After adjusting for potential confounders, the odds ratio (OR) for pterygium was greater in participants with higher total serum IgE levels (OR = 1.63; p = 0.047). Multivariable-adjusted ORs of pterygium across the tertile of increasing IgE were 1.00 (reference), 1.18, and 1.45, (P for linear trend = 0.038). Although the ORs for the upper two tertiles of cockroach and dog allergen-specific IgE were higher than those for the lowest tertile, allergen-specific serum IgE showed no clear association with pterygium.

CONCLUSIONS

Increased total serum IgE concentration is independently related to pterygium after adjusting for confounding factors. To the best of our knowledge, this study is the first research that reveals an association between serum IgE and pterygium.

Neuronal Fc-epsilon receptor I contributes to antigen-evoked pruritus in a murine model of ocular allergy

Pruritus is the major symptom of ocular allergy but currently available treatments are often ineffective. Previous studies demonstrated that subpopulations of primary sensory neurons express Fc receptors and may contribute to antigen-specific pain. We investigated the role of neuronal Fc-epsilon Receptor I (FcεRI) in allergic ocular pruritus. Ovalbumin (OVA) was used as allergen together with alum adjuvant (OVA+alum) to produce a mouse model of ocular allergy with a significant elevation in the serum levels of both antigen-specific IgE and IgG. Mice sensitized by OVA without alum only induced elevation of serum IgG but not IgE. Scratching behavior toward the eyes with the hindlimb was used as an indicator of ocular itch. Topical OVA challenging to the eye dose-dependently induced scratching toward the eye in the OVA+alum sensitized mice, but not those sensitized by OVA only. The antigen-induced scratching was largely abolished by topical application of the blocking antibody to FcεRIα, but was only partially alleviated by pretreatment of mast cell stabilizer or histamine I receptor antagonist. The expression of FcεRI was detected in subpopulations of trigeminal ganglion (TG) neurons including those expressing pruriceptive markers and innervating the conjunctiva in the naïve mice. Moreover, FcεRI was found significantly upregulated in small-sized TG neurons in the OVA+alum sensitized mice. In acutely dissociated TG neurons, IgE-immune complex (IC), but not the antibody or antigen alone, induced intracellular calcium increase. The neuronal responses to IgE-IC could be specifically blocked by pre-application of a siRNA for FcεRIα. Our results indicate that FcεRI expressed on peripheral nociceptive neurons in the TG may be directly activated by IgE-IC and contribute to allergic ocular pruritus. This study may suggest a novel mechanism for the development of pathological itch in allergic diseases.

Age-Related Cataract Is Associated with Elevated Serum Immunoglobulin E Levels in the South Korean Population: A Cross-Sectional Study

Background

Previous research has suggested that immunoglobulin E (IgE)-mediated events lead to several chronic diseases. We investigated the association between allergic conditions and age-related cataracts in the South Korean adult population.

Methods

A cross-sectional study was performed using data obtained from 1,170 participants aged 40 years or older who were enrolled in the Korean National Health and Nutrition Examination Survey 2010. Multivariable logistic regression was used to examine the relationship between age-related cataracts and allergic conditions, including total serum IgE and allergen-specific serum IgE levels, after adjustment for potential confounders (age, sex, alcohol consumption, smoking, sun exposure, blood pressure, plasma glucose and cholesterol levels, as well as histories of asthma, atopic dermatitis, and rheumatoid arthritis).

Results

After adjusting for potential confounders, the odds ratio (OR) for age-related cataract was greater in participants with higher total serum IgE levels (OR = 1.37; P = 0.044). In particular, increased IgE levels were significantly associated with nuclear cataract (OR = 1.42; P = 0.032). However, allergen-specific serum IgE levels did not differ significantly between groups. In the trend analysis, no significant relationship was observed between serum IgE and any type of age-related cataract.

Conclusion

Increased total serum IgE level is independently associated with age-related cataracts after adjustment for confounding factors.

House dust allergy and immunotherapy

HDM allergy is associated with asthma, allergic rhinitis and atopic dermatitis. In many countries childhood asthma is predominantly found in HDM-allergic children with their probability of developing disease being proportional to their IgE antibody titers and the early development of Th2 responses. While the pathogenesis is complex and increasingly linked to infection the immunologically-based allergen immunotherapy and anti-IgE antibody therapy are highly beneficial. Immunotherapy could be a short-term treatment providing lifelong relief but the current regimens depend on repeated administration of allergen over years. Immunological investigations point to a contribution of responses outside the Th2 pathway and multiple potential but unproven control mechanisms. Over half of the IgE antibodies are directed to the group 1 and 2 allergens with most of remainder to the group 4, 5, 7 and 21 allergens. This hierarchy found in high and low responders provides a platform for introducing defined allergens into immunotherapy and defined reagents for investigation.

Asthma 2008: targeting immunoglobulin E to achieve disease control

Traditionally, practice guidelines have recommended a step-wise approach to treatment based on asthma severity and lung function. However, increasing evidence suggests that asthma may not be adequately controlled in many patients with moderate-to-severe disease despite aggressive therapy, and that regularly evaluating the level of asthma control achieved in individual patients may be more effective than disease severity in guiding treatment decisions. This is reflected in updated asthma guidelines from the National Asthma Education and Prevention Program, which advocate regular assessment of asthma control in terms of the current impairment and future risk associated with the disease. Guideline-recommended options for patients with persistent, moderate-to-severe immunoglobulin E (IgE)-mediated asthma have recently been enhanced by the inclusion of omalizumab. This change is based on growing evidence for the central role of IgE in airway inflammation and asthma and the clinical effectiveness of blocking IgE with omalizumab, a recombinant humanized monoclonal antibody. Omalizumab significantly reduced asthma exacerbations and improved lung function and symptoms in randomized controlled studies of patients inadequately controlled on inhaled corticosteroids plus long-acting beta(2)-agonist therapy; these benefits for reducing asthma impairment and risk were maintained during steroid dose reductions. Omalizumab is well tolerated, although patients should be monitored for possible rare anaphylactic reactions.