The research team, led by investigators at Virant Diagnostics Laboratory and the Institute for Asthma and Allergy in Maryland, followed 32 peanut-allergic children aged 4 to 18 who underwent peanut oral immunotherapy at a single clinic between 2021 and 2025. Sixteen of the children had Ara h 2-specific IgE levels of 40 kU/L or higher — a threshold associated with severe, clinically significant peanut allergy — while the other 16 had lower values. Rather than the faster escalation schedules used in commercial protocols, every participant started at a mere 0.1 milligrams of peanut protein, roughly a ten-thousandth of a peanut’s worth, and climbed through 18 dose levels over a prolonged up-dosing phase lasting one to two years, with clinic visits spaced 14 to 28 days apart or longer.

The clinical results defied expectations for the high-risk group. By 24 months, 68.8 percent of the children with high Ara h 2-IgE had achieved effective desensitization, defined as safely consuming at least 300 milligrams of peanut protein daily — a benchmark estimated to shield against more than 95 percent of accidental exposures, which typically involve amounts well below 100 milligrams. The lower-IgE group fared no better and no worse, with 62.5 percent reaching the same goal. Nine children escalated further, exceeding 1,000 milligrams per day, and one tolerated up to 7,000 milligrams. Safety data were equally reassuring: despite the forbidding baseline antibody levels, only one severe reaction occurred in each subgroup across the entire study, no child discontinued treatment because of adverse events, and no cases of eosinophilic esophagitis emerged.

Alongside the clinical outcomes, the researchers pursued a question that has long frustrated the allergy field: can laboratory measurements tell whether immunotherapy is actually working inside a patient? No validated biomarker currently exists to predict who will succeed with oral immunotherapy or to monitor the desensitization process as it happens. The gold standard for measuring food allergy, the double-blind placebo-controlled oral food challenge, is resource-hungry and carries its own risks, so a blood test that captures immune change in real time would be transformative for both research and routine care.

The team focused on two candidate measures. The first is the basophil activation test, or BAT, a flow-cytometry technique that measures how strongly a patient’s basophils — the white blood cells that unleash histamine in allergic reactions — display the CD63 surface marker when exposed to escalating concentrations of peanut protein in a test tube. Because it interrogates effector-cell reactivity directly rather than merely quantifying antibodies, BAT offers a functional window into allergic potential. The second measure is the ratio of allergen-specific IgE, the antibody class that drives allergic reactions, to allergen-specific IgG4, a so-called blocking antibody that competes with IgE for allergen binding and is thought to dampen responses during immunotherapy.

What emerged was a dynamic, biphasic picture that static snapshots would have missed entirely. Basophil reactivity did not simply fade during treatment; it first spiked during the early up-dosing months, between months two and six, before progressively and significantly declining thereafter. Mixed-effects models accounting for repeated measurements within each participant confirmed a highly significant overall change over time, with suppression becoming statistically robust at 19 to 24 months and deepening further at 25 to 36 months. Even more telling, the activation threshold shifted stepwise upward: significant blunting of basophil responses appeared first at low peanut concentrations, then at intermediate doses, and finally even at the highest concentration tested — meaning that by the end of the study, a child’s basophils needed far more allergen to fire than they had at the start.

When the researchers compared the most recent BAT area under the curve during months 13 to 36 with each child’s maximum tolerated daily dose, a value below 100 was significantly associated with effective desensitization, achieving a sensitivity of 89.5 percent. Receiver operating characteristic analysis yielded an area under the curve of 0.784 for the continuous measure. The antibody story ran in parallel: peanut- and component-specific IgE rose transiently in the first months of therapy — at one point, 100 percent of participants exceeded 50 kU/L for peanut IgE — before drifting downward, while specific IgG4 climbed early and kept climbing, driving the IgE/IgG4 ratio down throughout treatment. A ratio below 50, reached by 72 percent of participants at 13 to 18 months, showed strong discriminatory performance with an ROC value of 0.836.

The authors are careful about what these thresholds can and cannot do. Baseline BAT and baseline IgE bore no relationship to eventual desensitization, and exploratory time-lagged analyses — asking whether biomarker values at 13 to 18 months predicted success at 19 to 24 months — did not establish prospective predictive power, with confidence intervals too wide to be conclusive. Both cutoffs were derived and tested within the same small cohort, a practice the researchers themselves flag as likely optimistic. The study was also single-center, retrospective, and lacked a control group, and it required participants to have completed treatment and at least two BAT measurements, a design that may have excluded early dropouts and inflated success rates. Desensitization was judged from routinely consumed doses rather than blinded food challenges.

Even so, the conceptual message may prove the study’s most durable contribution. The traditional approach to assessing food allergy — a single IgE number drawn before treatment begins — appears fundamentally limited, because the most informative signals are trajectories, not starting points. In this cohort, children whose IgE remained elevated at two years were nonetheless clinically desensitized, showing that serologic antibody decline lags behind functional improvement, sometimes by a wide margin. A clinician relying on IgE alone mid-treatment might wrongly conclude that therapy was failing when basophil suppression and rising IgG4 told a very different story.

For the growing number of families considering peanut oral immunotherapy, the findings carry a practical takeaway: patients with frighteningly high antibody levels are not automatically excluded from treatment, provided the protocol is paced to match their risk. Whether slow escalation genuinely improves safety compared with faster regimens, and whether longitudinal biomarker monitoring can be validated against standardized challenges in independent cohorts, remain open questions that the authors say must precede any clinical implementation. But the vision is clear — a future in which a series of blood draws, tracking basophils and antibody ratios over months, could give allergists and anxious parents a real-time readout of the immune system slowly learning to tolerate the very food that once threatened it.

Subject of Research: Longitudinal basophil activation testing and antibody biomarkers during low-dose, slow-escalation peanut oral immunotherapy in children with high Ara h 2-specific IgE

Article Title: Longitudinal basophil activation testing for assessing response to low-dose initiation, slow-escalation peanut oral immunotherapy in patients with high Ara h 2-sIgE

Article References: Chen, J., Yu, J. J., Yu, J., Wan, L., Chiao, J., Economides, A., Han, D., & Li, H. H. (2026). Longitudinal basophil activation testing for assessing response to low-dose initiation, slow-escalation peanut oral immunotherapy in patients with high Ara h 2-sIgE. Frontiers in Allergy, 7, Article 1902025. https://doi.org/10.3389/falgy.2026.1902025

Image Credits: AI Generated

DOI: 10.3389/falgy.2026.1902025

Keywords: peanut allergy, oral immunotherapy, basophil activation test, Ara h 2, desensitization, biomarkers, IgG4, food allergy, allergen immunotherapy, pediatrics, flow cytometry, anaphylaxis

Eosinophilic granulomatosis with polyangiitis, abbreviated EGPA and formerly called Churg-Strauss syndrome, is a rare form of vasculitis, meaning it involves inflammation of blood vessels. It belongs to a family of conditions known as antineutrophil cytoplasmic antibody, or ANCA, associated vasculitides, although not every patient produces these antibodies. The disease is characterised by an overabundance of eosinophils, a type of white blood cell normally deployed against parasites and involved in allergic reactions. When these cells accumulate and activate inappropriately, they can wreak havoc on organs throughout the body, including the lungs, skin, heart, and, critically, the peripheral nerves, the delicate wiring that carries signals between the spinal cord and the rest of the body.

Peripheral neuropathy, the medical term for damage to these nerves, is among the most feared manifestations of EGPA. Patients may experience numbness, tingling, weakness, or excruciating pain, typically beginning in the feet and hands. In the most severe cases, the damage follows a pattern known as mononeuritis multiplex, in which multiple individual nerves fail in unpredictable succession, leaving patches of the body paralysed or insensate. Despite decades of clinical observation, the underlying mechanisms that drive nerve injury in EGPA remain poorly understood, and clinicians have lacked dependable laboratory markers to identify which patients are developing or will develop this complication.

The new study, published in the Journal of Neurology, set out to address this gap. Researchers led by Yuichi Masuda and Shogo Matsuda of Osaka Medical and Pharmaceutical University, together with collaborators at Kyoto University, Osaka Metropolitan University, Yodogawa Christian Hospital, Tenri Hospital, and Kurashiki Sweet Hospital, assembled data from the REVEAL cohort, a multicentre database covering patients diagnosed across Japan. They enrolled individuals newly diagnosed with EGPA between 2006 and 2024, applying the 2022 classification criteria jointly developed by the American College of Rheumatology and the European Alliance of Associations for Rheumatology, the current international standard for identifying the disease.

From an initial pool of 159 patients in the REVEAL cohort, the investigators focused on 107 patients who were newly diagnosed and had not yet received any treatment, a design choice that eliminates the confounding effects of prior immunosuppressive therapy on laboratory values and clinical findings. The results were striking. Peripheral neuropathy was present in 93 of the 107 patients, an extraordinary 86.9 percent, underscoring just how central nerve involvement is to the clinical picture of EGPA in this Japanese population. Meanwhile, 45 patients, or 42.1 percent, tested positive for myeloperoxidase ANCA, one of the two major antibody types associated with this disease family.

When the researchers compared patients with neuropathy against those without, several laboratory parameters stood out. Patients with peripheral nerve involvement had significantly higher levels of white blood cells, eosinophils, serum immunoglobulin G, and serum immunoglobulin G4 at the time of diagnosis. Among these candidates, IgG4 emerged as the most useful clinical indicator for detecting neuropathy in EGPA patients. This finding carries particular biological interest. IgG4 is an unusual antibody subclass, associated with immune tolerance rather than aggressive inflammation, and it has previously been implicated in IgG4-related disease, a distinct fibroinflammatory condition. Earlier work had already documented IgG4 immune responses in Churg-Strauss syndrome, and pathological studies have found IgG4-related features in inflammatory neuropathies, making the new cohort data a compelling piece of a growing puzzle.

The study also examined what happens to patients over time, and here the news was mixed. Using Kaplan-Meier survival analysis, a standard statistical technique for tracking events over follow-up periods, the team calculated that the five-year relapse rate of peripheral neuropathy among EGPA patients who had experienced it was 18.6 percent. In other words, nearly one in five patients whose nerve disease had initially been brought under control saw it return within five years. Relapse in vasculitis is a persistent clinical challenge, and identifying which patients are at risk has been an ongoing goal of international research efforts, including the European Vasculitis Study Group trials, which previously documented the burden of peripheral neuropathy in ANCA-associated vasculitis more broadly.

Perhaps the most actionable finding concerned treatment. The researchers found that the administration rate of intravenous cyclophosphamide, a potent immunosuppressive drug long used in severe forms of vasculitis, was significantly lower among patients whose neuropathy relapsed than among those who remained in remission. While the observational design of the study means it cannot definitively prove that cyclophosphamide prevents relapse, the association suggests that more aggressive induction therapy at the outset may protect the nerves over the long term. This aligns with contemporary European guidelines for managing ANCA-associated vasculitis, which recommend cyclophosphamide or rituximab for organ-threatening disease, and with recent trials exploring glucocorticoids combined with cyclophosphamide in EGPA patients with poor-prognosis factors.

The implications for clinical practice are potentially significant. A readily available serum marker like IgG4 could help clinicians stratify newly diagnosed EGPA patients, flagging those who need close neurological monitoring, nerve conduction studies, or early escalation of immunosuppression. It could also complement existing prognostic tools, such as the revised five-factor score used to assess mortality risk in systemic necrotizing vasculitides, and disease activity measures like the Birmingham Vasculitis Activity Score version 3.0, which the current study used to characterise patients at baseline. For a disease in which diagnosis is often delayed for years while patients are treated for asthma alone, any additional diagnostic lever is welcome.

Caution is nonetheless warranted. The study involved 107 patients from a single country, and the authors themselves note that the aetiology of peripheral neuropathy in EGPA remains unclear. Whether IgG4 is merely a correlate of the eosinophilic, ANCA-negative disease subset that tends toward neuropathy, or plays a direct role in nerve injury, awaits further mechanistic work. The finding that lower cyclophosphamide use was associated with relapse could reflect confounding by disease severity, since physicians may reserve the drug for the sickest patients. Still, with newer targeted therapies such as the anti-interleukin-5 agent mepolizumab showing promise for EGPA-related neuropathy in recent reports, the landscape of treatment options is expanding. The REVEAL cohort study adds an important piece of evidence to this evolving picture, offering clinicians a potential biomarker and a hint that early, intensive immunosuppression may keep patients’ nerves, and their independence, intact for longer.

Subject of Research: Peripheral neuropathy in eosinophilic granulomatosis with polyangiitis

Article Title: Clinical features and prognosis of EGPA-associated peripheral neuropathy: a multicentre REVEAL cohort study

Article References: Masuda, Y., Matsuda, S., Okazaki, A., Tsuge, R., Manabe, A., Taniguchi, T., Hiwa, R., Hatta, M., Shiomi, M., Watanabe, R., Suwa, N., Fujiki, Y., Miyake, H., Yamamoto, W., Hashimoto, M., Takeuchi, T., & Kotani, T. (2026). Clinical features and prognosis of EGPA-associated peripheral neuropathy: a multicentre REVEAL cohort study. Journal of Neurology, 273(10), Article 641. https://doi.org/10.1007/s00415-026-14196-z

Image Credits: AI Generated

DOI: 10.1007/s00415-026-14196-z

Keywords: EGPA, peripheral neuropathy, vasculitis, IgG4, ANCA, cyclophosphamide, eosinophils, autoimmune disease, REVEAL cohort, biomarker, relapse, Journal of Neurology