D1.206 - Local allergic rhinitis to birch pollen: a case of transient IgE+ plasmablast detection and successful sublingual immunotherapy

Introduction: Local allergic rhinitis (LAR) is a clinically controversial phenotype of allergic rhinitis. While a multi-tool diagnostic approach exists, including the nasal provocation test (NPT), local IgE assessment, nasal cytology, and the basophil activation test (BAT), these tools are not yet widely adopted in routine practice. This gap necessitates the development and validation of novel, more accessible diagnostic methods.

Case description: We present the case of a 45 year old female patient with a long standing history of seasonal rhinitis symptoms clinically suggestive of birch pollen allergy. Standard allergy testing, including skin prick test and serum specific IgE to birch pollen extract and its components, showed negative results. To confirm LAR, a multi tool diagnostic approach was performed. Only the NPT with a 1:2 dilution of birch pollen extract yielded a positive result (Table 1).  To resolve this diagnostic uncertainty, we performed flow cytometry on a peripheral blood sample collected during the birch pollen season. This analysis successfully identified a population of allergen-specific IgE⁺B-cells. Based on these combined findings, a diagnosis of LAR to birch pollen was established. The patient subsequently commenced birch pollen sublingual allergen immunotherapy (SLIT). After two years of SLIT, her seasonal symptoms showed significant improvement, resulting in a reduced need for symptomatic therapy.

Discussion: Although a multi-tool approach is employed for LAR, the NPT is currently considered the only confirmatory diagnostic method. In the present case, we detected a transient population of Bet v 1-specific IgE⁺CD27⁺⁺CD38⁺⁺B-cells (phenotypically consistent with plasmablasts) in the patient’s blood during the pollen season, which was no longer detectable two months post-season. This finding underscores the detection of circulating IgE+ plasmablasts as a promising direction for elucidating LAR pathogenesis. Furthermore, the patient's treatment with two years of birch pollen SLIT led to significant clinical improvement and symptom reduction.

Conclusion: The investigation of allergen-specific IgE⁺ B-lymphocytes is warranted in cases where standard methods fail to confirm an IgE-mediated allergy, such as LAR. Detection of these cells in peripheral blood during the pollen season opens new avenues for understanding the disease mechanisms and improving diagnostic strategies for allergic conditions.