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