Changes in the Th9 cell population and related cytokines in the peripheral blood of infants with recurrent wheezing

Introduction
T helper type 9 (Th9) cells have been shown to play a key role in initiating allergic reactions and promoting airway inflammation. However, to the best of our knowledge, their role has not been analyzed in infants with recurrent wheezing.

Material and methods
We performed a case-control study including 34 infants with recurrent wheezing and the same number of healthy infants as controls; all subjects were aged 1- to 3-years-old. The Th9 cell populations in the peripheral blood of these subjects were analyzed using flow cytometry, along with the assessment of Th9- and Th2-related plasma cytokine levels, including interleukin (IL)-1b, IL-4, IL-5, IL-9, IL-10, IL-13, IL-17A, and IL-33, and transforming growth factor b1 (TGF-b1) using a Luminex 200 immunoassay.

Results
Our results indicated that infants with recurrent wheezing had higher percentages of Th9 cells (median, 0.69%; range, 0.46-1.08%) as compared to healthy infants (median, 0.25%, range, 0.13-0.36%; p < 0.05). In addition, infants with recurrent wheezing also exhibited higher plasma levels of cytokines IL-4, IL-9, IL-10, IL-33, and TGF-b1. Furthermore, the percentage of Th9 cells was positively correlated with the levels of IL-4 (r = 0.408, p < 0.05) and IL-9 (r = 0.644, p < 0.05) in the peripheral blood of wheezing infants.

Conclusions
Our findings suggest that the percentage of Th9 cells is increased in infants with recurrent wheezing; thus, Th9 cells may play an important role in the pathogenesis of recurrent wheezing.