IgG Antibodies in Food Allergy Influence Allergen–Antibody Complex Formation and Binding to B Cells: A Role for Complement Receptors

Abstract

Allergen–IgE complexes are more efficiently internalized and presented by B cells than allergens alone. It has been suggested that IgG Abs induced by immunotherapy inhibit these processes. Food-allergic patients have high allergen-specific IgG levels. However, the role of these Abs in complex formation and binding to B cells is unknown. To investigate this, we incubated sera of peanut- or cow’s milk–allergic patients with their major allergens to form complexes and added them to EBV-transformed or peripheral blood B cells (PBBCs). Samples of birch pollen-allergic patients were used as control. Complex binding to B cells in presence or absence of blocking Abs to CD23, CD32, complement receptor 1 (CR1, CD35), and/or CR2 (CD21) was determined by flow cytometry. Furthermore, intact and IgG-depleted sera were compared. These experiments showed that allergen–Ab complexes formed in birch pollen, as well as food allergy, contained IgE, IgG1, and IgG4 Abs and bound to B cells. Binding of these complexes to EBV-transformed B cells was completely mediated by CD23, whereas binding to PBBCs was dependent on both CD23 and CR2. This reflected differential receptor expression. Upon IgG depletion, allergen–Ab complexes bound to PBBCs exclusively via CD23. These data indicated that IgG Abs are involved in complex formation. The presence of IgG in allergen–IgE complexes results in binding to B cells via CR2 in addition to CD23. The binding to both CR2 and CD23 may affect Ag processing and presentation, and (may) thereby influence the allergic response.

Serological Investigation of Food Specific Immunoglobulin G Antibodies in Patients with Inflammatory Bowel Diseases

“…It has been reported that mast cells can respond not only to IgE antibodies but also to IgG antibodies [37] . In addition IgG antibodies in food allergy may even influence allergen-IgE complex formation and bind to B cells, which is quite opposite the traditional concept that IgG antibodies are supposed to inhibit these processes [38] . Therefore IgG antibodies probably serve as mediation effects rather than inhibition in hypersensitivity reaction caused by food intolerance.…”

Is mealworm or shrimp allergy indicative for food allergy to insects?

“…One shrimp allergic patient was not able to participate as a result of emigration. BAT's were performed as described previously by Meulenbroek et al [13] with minor modifications. Cells were incubated with a dilution series (1:10 7 to 1:10 2 ) of insect extracts (5 mg/mL).…”

IgG4 and IgE Transcripts in Childhood Allergic Asthma Reflect Divergent Antigen-Driven Selection

“…IgG4-producing cells can undergo secondary class switch to IgE (31), as was shown also for IgG1 in mice (32); thus, a fraction of the IgE repertoire may reflect a subset of the IgG4 repertoire in humans. Although IgG4 seems to mediate tolerance during successful treatment in allergic patients, its function during allergen-Ab complex formation in food allergies is unknown (33). Moreover, IgG4 can also mediate autoimmunity (e.g., pemphigus vulgaris) and might play a pathogenic role in newly identified "IgG4-related disease" (34).…”