Background: Interleukin-17A (IL-17A)-producing CD4+T helper cells have been implicated in allergic inflammation; however, the role of IL-17A in allergic rhinitis (AR) patients with different degrees of atopy and airway reactivity to methacholine (Mch) has not been examined.

Objectives: To explore IL-17A-producing CD3+CD4+T cells in peripheral blood of patients with persistent AR and assess the degree of atopy, eosinophil count (Eo count), and bronchial hyper-responsiveness (BHR) to methacholine.

Methods: The study involved 61 patients and 30 controls. The percentage of CD3+CD4+IL-17A+T cells in peripheral blood was measured by flow cytometry, bronchial challenges with Mch were performed, as was skin prick tests with standard inhalant allergens, and Eo count was measured. Atopic status was determined by the number of positive SPT results and wheal mean diameter.

Results: A statistically significant difference in Th17 cell percentage was found in the AR and control groups (2.59 ± 1.32% and 1.24 ± 0.22% respectively, P = 0.001). Forty-one patients (67.2%) were polysensitized to indoor and outdoor allergens, while 20 (32.8%) had positive skin prick tests to indoor allergens. CD4+T cells were significantly higher in the patient group compared to the control group (2.91 ± 1.5% versus 1.91 ± 0.62%, P = 0.005), as was Eo count (4.48 ± 2.13 vs. 2.32 ± 1.83) (P = 0.0001). Forty-one in the AR group (67%) and 7 (23%) in the control group were Mch-positive (P = 0.001). The percentage of IL-17A-producing CD4+T cells was significantly higher in males compared to females (3.15 ± 1.8% versus 2.31 ± 0.9%, P = 0.02)

Conclusions: Polysensitized AR patients exhibited higher IL-17A-producing CD4+T cell levels and eosinophil counts. Male patients displayed a higher frequency of IL-17A-producing T cells.