High frequency of circulating follicular helper T cells in patients with bronchial asthma.

Background: Bronchial asthma is a chronic airway inflammatory disease primarily characterized by an abnormality in the IgE pathway. Follicular helper T (Tfh) cells are the specialized subset indispensible for providing cognate help to B cells during formation of germinal centers. The more recent work presents clear evidence that human blood CD4(+) CXCR5(+) T cells, circulating Tfh (cTfh) cells, are counterparts of Tfh cells in germinal centers. Methods: 11 patients with mild asthma, 15 severe asthma patients, and 20 healthy controls were enrolled in this study. The percentages of cTfh cells were assessed by flow cytometry. The correlation between the percentage of cTfh cells and the level of serum total IgE was also analyzed. Additionally, the serum level of IL-21 was quantified by ELISA. Expression of Bcl-6 mRNA and IL-21 mRNA were assayed by real-time polymerase chain reaction. Results: The frequency of the cTfh cells was significantly higher in severe asthma than in mild asthma patients and in healthy individuals and positively correlated with total IgE in blood. Furthermore, expression of Bcl-6 mRNA and plasma IL-21 concentrations in asthma patients was increased. Conclusions: Our findings provide evidence of increased frequency of cTfh cells in asthma patients, which implies that this cell subset might play an important role in the pathogenesis of asthma.