Circulating TFH2 Cell Expansion and GZMK⁺ TFH1 Cells are Associated with Allergic Rhinitis

Allergic rhinitis (AR) is a prevalent condition characterized by an immunoglobulin E (IgE)-mediated immune response. T follicular helper (TFH) cells regulate B-cell differentiation and antibody production, and circulating TFH2 cells are closely associated with type 2 humoral immunity and IgE-related responses in AR. However, whether AR is marked by isolated TFH2 expansion or broader remodeling of circulating TFH (cTFH) subsets, including TFH1-related heterogeneity, remains unclear.

A total of 56 participants were enrolled, including 39 patients with AR and 17 healthy controls (HC). Flow cytometry was performed in 36 patients with AR and 14 HC to quantify cTFH subsets and activation states. Single-cell RNA sequencing (scRNA-seq) was conducted in an independent exploratory cohort comprising 3 patients with AR and 3 HC to characterize TFH transcriptional heterogeneity, based on canonical transcriptional programs.

Flow cytometry demonstrated that cTFH2 cell frequencies were significantly increased in patients with AR and positively correlated with disease severity. Activated CCR7^low PD-1^high cTFH cells were also elevated, indicating enhanced TFH activation. Further scRNA-seq analysis identified six transcriptionally distinct TFH clusters, with TFH2-like transcriptional signatures enriched in patients with AR, consistent with flow cytometric findings. Notably, a GZMK⁺ TFH1 subset, enriched in cytotoxic genes, including GZMK, CCL5, and GZMA, was more abundant in patients with AR, a result corroborated by flow cytometry.

This study demonstrates the expansion of cTFH2 and GZMK⁺ TFH1 subsets in patients with AR and highlights the phenotypic and transcriptional heterogeneity of cTFH cells. These findings suggest that peripheral TFH profiling may aid in characterizing systemic immune alterations in allergic inflammation. The scRNA-seq results should be interpreted as exploratory due to the limited sample size.