Food allergies are a major clinical problem and are driven by IgE antibodies (Abs) specific for food antigens (Ags). T follicular regulatory (Tfr) cells are a specialized subset of FOXP3⁺ T cells that modulate Ab responses. Here, we analyzed the role of Tfr cells in regulating Ag-specific IgE using a peanut-based food allergy model in mice. Peanut-specific IgE titers and anaphylaxis responses were significantly blunted in Tfr cell–deficient Foxp3-Cre Bcl6^fl/fl mice. Loss of Tfr cells led to greatly increased nonspecific IgE levels, showing that Tfr cells have both helper and suppressor functions in IgE production in the germinal center (GC) that work together to facilitate the production of Ag-specific IgE. Foxp3-Cre Pten^fl/fl mice with augmented Tfr cell responses had markedly higher levels of peanut-specific IgE, revealing an active helper function by Tfr cells on Ag-specific IgE. The helper function of Tfr cells for IgE production involves IL-10, and the loss of IL-10 signaling by B cells led to a severely curtailed peanut-specific IgE response, decreased GCB cell survival, and loss of GC dark zone B cells after peanut sensitization. We thus reveal that Tfr cells have an unexpected helper role in promoting food allergy and may represent a target for drug development.

Background: Allergic reactions to peanuts (Arachis hypogaeaL.) can cause severe symptoms and in some cases can be fatal, but avoidance is difficult due to the prevalence of peanut-derived products in processed foods. One strategy of reducing the allergenicity of peanuts is to alter or eliminate the allergenic proteins through mutagenesis. Other seed quality traits could be improved by altering biosynthetic enzyme activities. Targeting Induced Local Lesions in Genomes (TILLING), a reverse-genetics approach, was used to identify mutations affecting seed traits in peanut.Results: Two similar copies of a major allergen gene,Ara h 1, have been identified in tetraploid peanut, one in each subgenome. The same situation has been shown for major allergenAra h 2. Due to the challenge of discriminating between homeologous genes in allotetraploid peanut, nested PCR was employed, in which both gene copies were amplified using unlabeled primers. This was followed by a second PCR using gene-specific labeled primers, heteroduplex formation, CEL1 nuclease digestion, and electrophoretic detection of labeled fragments. Using ethyl methanesulfonate (EMS) as a mutagen, a mutation frequency of 1 SNP/967 kb (3,420 M₂individuals screened) was observed. The most significant mutations identified were a disrupted start codon inAra h 2.02and a premature stop codon inAra h 1.02. Homozygous individuals were recovered in succeeding generations for each of these mutations, and elimination of Ara h 2.02 protein was confirmed. Several Ara h 1 protein isoforms were eliminated or reduced according to 2D gel analyses. TILLING also was used to identify mutations in fatty acid desaturaseAhFAD2(also present in two copies), a gene which controls the ratio of oleic to linoleic acid in the seed. A frameshift mutation was identified, resulting in truncation and inactivation of AhFAD2B protein. A mutation inAhFAD2Awas predicted to restore function to the normally inactive enzyme.Conclusions: This work represents the first steps toward the goal of creating a peanut cultivar with reduced allergenicity. TILLING in peanut can be extended to virtually any gene, and could be used to modify other traits such as nutritional properties of the seed, as shown in this study.

Peanut allergy has garnered significant attention because of the high sensitization rate, increase in allergy, and severity of the reaction. Sufficiently reliable therapies and efficient mitigating techniques to combat peanut allergy are still lacking. Current management relies on avoiding peanuts and nuts and seeds with homologous proteins, although adverse events mostly occur with accidental ingestion. There is a need for hypoallergenic peanut products to protect sensitized individuals and perhaps serve as immunotherapeutic products. Alongside traditional practices of thermal and chemical treatment, novel processing approaches such as high‐pressure processing, pulsed ultraviolet light, high‐intensity ultrasound, irradiation, and pulsed electric field have been performed toward reducing the immunoreactivity of peanut. Covalent and noncovalent chemical modifications to proteins also have the tendency to alter peanut allergenicity. Enzymatic hydrolysis seems to be the most advantageous technique in diminishing the allergenic potential of peanut. Furthermore, the combined processing approach (hurdle technologies) such as enzymatic hydrolysis followed by, or in conjunction with, roasting, high pressure and heat, ultrasound with enzymatic treatment, or germination have shown a significant reduction of peanut immunoreactivity and may emerge as useful techniques in reducing the allergenicity of peanut and other foods. This study represents our current knowledge about the alterations in allergenic properties of peanut via different processing mechanisms as well as evaluating its future potential, geographical based data on increasing sensitization, clinical relevance, eliciting dose, and current management of peanut allergy. Furthermore, the molecular characteristics and clinical relevance of peanut allergens have been discussed.

Background: Understanding the discrepancy between IgE sensitization and allergic reactions to peanut could facilitate diagnosis and lead to novel means of treating peanut allergy.Objective: To identify differences in IgE and IgG4 binding to peanut peptides between peanut‐allergic (PA) and peanut‐sensitized but tolerant (PS) children.Methods: PA (n = 56), PS (n = 42) and nonsensitized nonallergic (NA, n = 10) patients were studied. Synthetic overlapping 15‐mer peptides of peanut allergens (Ara h 1‐11) were spotted onto microarray slides, and patients’ samples were tested for IgE and IgG4 binding using immunofluorescence. IgE and IgG4 levels to selected peptides were quantified using ImmunoCAP. Diagnostic model comparisons were performed using likelihood‐ratio tests between each specified nominal logistic regression models.Results: Seven peptides on Ara h 1, Ara h 2, and Ara h 3 were bound more by IgE of PA compared to PS patients on the microarray. IgE binding to one peptide on Ara h 5 and IgG4 binding to one Ara h 9 peptide were greater in PS than in PA patients. Using ImmunoCAP, IgE to the Ara h 2 peptides enhanced the diagnostic accuracy of Ara h 2‐specific IgE. Ratios of IgG4/IgE to 4 out of the 7 peptides were higher in PS than in PA subjects.Conclusions: Ara h 2 peptide‐specific IgE added diagnostic value to Ara h 2‐specific IgE. Ability of peptide‐specific IgG4 to surmount their IgE counterpart seems to be important in established peanut tolerance.