Frequencies of circulating CD4+CD25+CD127low cells in atopics are altered by bronchial allergen challenge

Abstract

Recent studies in rodents revealed that regulatory T cells (T reg cells) with CD4+CD25+ phenotype can exert suppressive effects on experimentally-induced allergic airway inflammation and airway hyper-reactivity. It is unclear however, whether modulations of bronchoconstriction responses in human subjects might be related to T reg cells. We report here for the first time the changes in frequency of circulating lymphocytes with putative T reg cell phenotype (CD4+CD25+CD127low) in relation to bronchoconstriction phenotype following an intrabronchial allergen challenge. Thirty-one house dust mite sensitive patients were challenged with Dermatophagoides pteronyssinus extract (Dp). Eleven isolated early responders (IER) were compared with nine dual (early and late) responders (DR) and to 11 non-responders (NR). Frequencies of peripheral blood CD4+CD25+CD127low lymphocytes were assessed in all groups of patients by using three-parameter flow cytometry before, and six and 24 h, after allergen inhalation. At baseline, frequencies of CD4+CD25+CD127low lymphocytes were not statistically different among NR, IER and DR. When all individuals were analyzed together, a statistically significant decrease in frequency of CD4+CD25+CD127low lymphocytes was observed 6 h after the bronchial challenge. Interestingly, such a pattern was found consistently only in NR, while IER and DR displayed varying responses resulting in a trend similar to that of NR. Twenty-four hours after the bronchial challenge, frequencies of CD4+CD25+CD127low lymphocytes in all groups tended to return to baseline values. Our data indicate that bronchial allergen inhalation in sensitive patients (predominantly in those who did not develop significant bronchoconstriction) is associated with a decrease of proportion of peripheral lymphocytes with regulatory T cell phenotype.