Characterization of T cell subpopulations involved in the pathogenesis of asthma and allergic diseases.

Allergic asthma is a complex and heterogeneous disease which is characterized by intermittent reversible airway obstruction, chronic inflammation of the airways, bronchial hyperreactivity and an infiltration of lymphocytes and eosinophils into the airway submucosa. Animal models and clinical studies in humans have indicated an important role for T helper type 2 lymphocytes, producing IL-4, IL-5 and IL-13, in the pathogenesis of this disorder. However, although IL-4 and IL-13 have strong anti-inflammatory properties, the physiologic anti-inflammatory Th2 response does not seem to be operational in allergic asthma. Moreover, the induction of a Th1 response seems to aggravate, rather than ameliorate, its inflammatory character. This article will focus on the involvement of T lymphocyte subpopulations in the pathogenesis of allergic asthma and allergic diseases. In addition, a potential role of the subpopulation(s) of T regulatory cells in the induction and/or maintaince of the disease process will be discussed.