beta 2-agonist exerts differential effects on the development of cord blood T cells but not on peripheral blood T cells

Asthma is a chronic inflammatory disease characterized by reversible airway obstruction caused by edematous airway lining, thickened mucosal secretion s, and smooth muscle constriction. beta2-adrenoceptor agonists are widely u sed in the treatment of bronchial asthma because of their ability to induce relaxation of airway smooth muscle. Evidence indicates that desensitizatio n and down-regulation of beta -adrenoceptors occurs in long-term beta2-agon ist therapy, and these medications were thought to cause increased severity of, and mortality in, asthma. The purpose of this study was to delineate f urther the potential adverse effects of beta2-agonists on the development o f T lymphocytes. T cells isolated from umbilical cord blood and adult perip heral blood were cultured in the presence of salbutamol. Intracellular stai ning with fluorescence-labeled antibodies was used to differentiate the fre quency of type 1 T-helper (Th1) and type 2 T-helper (Th2) cells. The result s showed a statistically significant inverse relationship between the conce ntration of salbutamol and the ratio of Th1 over Th2 on cord blood T cells. However, this trend was not observed in adult peripheral blood T cells, Th e data revealed another potential adverse effect in which chronic beta2-ago nist exposure predisposed differentiation of T lymphocytes towards Th2 whil e that of Th 1 was relatively suppressed, especially in cord blood T cells. Hence, beta2-agonists, despite their effect in symptomatic rescue in asthm a, should not be used indiscriminately as long-term therapeutic agents.