This factor plays an essential role in the function of the regulatory T cells that control Th1 and Th2 immune responses [33], and Borrego et al. have reported that, in comparison with healthy children, CTLA4 expression is diminished in wheezy subjects and those at high risk of asthma, thus suggesting that impaired CTLA4 expression may play a role in reducing bronchial obstruction [34]. Here, CTLA4 is linked to asthma.