Histology-Based Blood Leukocyte Profiling Reveals Parallel Th2 and Th17 Signatures in Seasonal Allergic Rhinitis

Abstract

Background : Allergic rhinitis (AR) is one of the most common medical conditions in the westernized world. Recent data suggest AR to be far more immunologically complex than the archetypical allergic Th2-driven eosinophilic inflammation and new methodological approaches are needed to decode this complexity. Methods : This study explores a novel histology-based analysis of circulating leukocytes for detailed profiling of immune cells using routine clinical blood samples. In brief, leukocytes were purified with minimal ex-vivo artefacts, embedded into agarose-paraffin pellets and sectioned for cutting-edge immunohistochemistry-based immune cell profiling. Blood leukocyte mapping was performed in 16 patients with seasonal AR outside and during the birch pollen season. Results : Our methodological feasibility test confirmed that the > 5000 cross sectioned leukocytes typically present in a pellet section had well preserved morphology and cell marker epitopes, allowing for robust quantitative analysis of immune-stained slides. Blood leukocyte samples collected during the allergen season had statistically higher levels of markers for eosinophils, neutrophils, monocytes and CD8 lymphocytes compared to the off-season baseline. No change was observed for CD20 B-lymphocytes, total CD3 T cells and basophils. Subclassification of CD4+ T-helper cells demonstrated a parallel and significant expansion of Th2 and Th17 cells during the pollen season, while Th1 cells remained unchanged. Whereas absolute basophils numbers were unaltered, a significant increase of the basophil markers GATA2 and CPA3 was observed during the pollen season. Conclusions: Apart from representing a positive method feasibility validation, our study provides further evidence of complex and parallel Th2 and Th17 immune signatures in seasonal AR. Our data also forward GATA2 and basophil CPA3 as potential biomarkers for ongoing allergic inflammation. It is thus proposed that the present histology-based approach, with its broad applicability, represents a powerful tool for decoding systemic immune alterations and guide novel biomarker strategies for improved personalized medication.