IL-17RB+ granulocytes are associated with airflow obstruction in asthma

Abstract

Background: Interleukin (IL)-25 (IL-17E) is a proinflammatory cytokine that plays an important role in the T-helper type 2 cell pathway. The effects of IL-25 are mediated by its specific receptor, IL-17RB. Previous studies have defined an IL-17RB⁺ granulocyte population known as type 2 myeloid (T2M) cells that express T-helper type 2 cell cytokines. The correlation of IL-17RB⁺ granulocytes, T2M cells, and asthma parameters is unknown.

Objective: To investigate the relation of IL-17RB⁺ granulocytes (and its subset, T2M cells) in patients with asthma with clinical parameters including spirometric values and the Asthma Control Test (ACT).

Methods: Peripheral blood from subjects with asthma and healthy controls was collected and analyzed by flow cytometry. Granulocytes were gated for IL-17RB⁺, T2M (CD11b⁺CD16⁺CD177⁺IL-17RB⁺), and eosinophil (CD16^-) populations. Spirometry testing was performed on subjects with asthma. ACT scores and medical histories were collected by questionnaire and chart review. Correlations of IL-17RB⁺ cells and T2M cells with spirometry and ACT score were analyzed.

Results: Percentages of IL-17RB⁺ granulocytes and T2M cells were larger in subjects with asthma than in controls. Furthermore, percentages of the 2 cell populations were negatively correlated with degree of airway obstruction as measured by the ratio of percentage-predicted forced expiratory volume in 1 second to force vital capacity (r = -0.17, P = .043 for IL-17RB⁺ granulocytes; r = -0.32, P = .03 for T2M cells). There was no correlation with ACT score. The percentage of eosinophils was increased in subjects with asthma. However, IL-17RB⁺ eosinophil percentages were similar between subjects with asthma and controls and did not correlate with any clinical parameter.

Conclusion: IL-17RB⁺ granulocytes and T2M cells from peripheral blood were increased in subjects with asthma, and the 2 cell types correlated with degree of airflow obstruction.