Changes in circulating follicular helper T-cells in Chinese patients with allergic rhinitis

Roles of follicular helper and regulatory T cells in allergic diseases and allergen immunotherapy

Allergic diseases are characterized by overactive type 2 immune responses to allergens and immunoglobulin E (IgE)-mediated hypersensitivity. Emerging evidence suggests that follicular helper T (T_FH ) cells, rather than type 2 T-helper (T_H 2) cells, play a crucial role in controlling IgE production. However, follicular regulatory T (T_FR ) cells, a specialized subset of regulatory T (T_REG ) cells resident in B-cell follicles, restricts T_FH cell-mediated help in extrafollicular antibody production, germinal center (GC) formation, immunoglobulin affinity maturation, and long-lived, high-affinity plasma and memory B-cell differentiation. In mouse models of allergic asthma and food allergy, CXCR5⁺ T_FH cells, not CXCR5^- conventional T_H 2 cells, are needed to support IgE production, otherwise exacerbated by CXCR5⁺ T_FR cell deletion. Upregulation of T_FH cell activities, including a skewing toward type 2 T_FH (T_FH 2) and IL-13 producing T_FH (T_FH 13) phenotypes, and defects in T_FR cells have been identified in patients with allergic diseases. Allergen immunotherapy (AIT) reinstates the balance between T_FH and T_FR cells in patients with allergic diseases, resulting in clinical benefits. Collectively, further understanding of T_FH and T_FR cells and their role in the immunopathogenesis of allergic diseases creates opportunities to develop novel therapeutic approaches.

Reduced CD4+T Cell CXCR3 Expression in Patients With Allergic Rhinitis

While T cells are considered to play a primary role in IgE-mediated atopic diseases, little is known about the systemic variations of T cell subsets from patients with allergic rhinitis (AR). To elucidate the characteristics of peripheral T cells, we analyzed natural killer, B cell, and T cell populations, performed T cell subset construction, and assessed chemokine receptor and associated serum cytokine expression in 25 AR patients and 20 healthy controls. Our results revealed increased levels of CD4⁺T cells, serum interleukin (IL)-10, IL-6, and interferon (IFN)-γ, and reduced Th1 and Th17 subsets, identified by their chemokine receptors, in AR patients. These results suggest a systemic activation of T cell responses in AR. We further demonstrated that AR patients exhibit significantly reduced CD4⁺T cell CXCR3 expression, especially in patients with moderate-severe disease severity, demonstrating that CXCR3 is a potential key molecule that hinders the Th1/Th2 balance in AR pathology. Overall, systemic T cell activation occurred in AR patients and CXCR3 dramatically decreased in CD4⁺T cells, which may ultimately be used as a potential disease and/or therapeutic target.

Role of allergen-specific T-follicular helper cells in immunotherapy

PURPOSE OF REVIEW

The discovery of novel T-cell subsets including follicular helper T (Tfh) cells has broadened our knowledge on the complex immune networks in allergic diseases. This review summarizes the evidence for Tfh cells in controlling immune responses to allergens with a particular focus on immunoglobulin E (IgE) production and discusses the implication of such regulation in allergen-specific immunotherapy.

RECENT FINDINGS

Tfh cells support the production of IgE in animal models for allergic diseases. Among Tfh cells, the type 2 subset (Tfh2) is considered as the major player that secretes IL-4 and promotes the isotype switching to IgE. In human inflammatory airway diseases, including allergic rhinitis, asthma, and nasal polyps, the increased frequencies of circulating or tissue Tfh2 cells have been reported. Notably, the frequencies of Dermatophagoides pteronyssinus group 1 (Der p 1)-specific IL-4 Tfh cells in blood positively correlated with serum Der p-specific IgE levels in allergic rhinitis patients. After allergen immunotherapy (AIT), Der p 1-specific IL-4 Tfh cells declined in allergic rhinitis patients, which associated with the remission of clinical symptoms.

SUMMARY

Allergen-specific IL-4 Tfh cells contribute to the production of allergen-specific IgE and correlate with clinical efficacy of AIT in allergic rhinitis patients, which suggest allergen-specific Tfh cells as a promising therapeutic target and biomarker for AIT in allergic rhinitis.