Defective immunological suppression can be a cause of the inflammation that leads to an allergic condition such as asthma. Suppressor regulatory T cells (Tregs) are essential for inducing and maintaining immunological tolerance to foreign and self-antigens, including allergens. Tregs are apparently altered in number and function in allergic asthmatic patients. Some treatments that ameliorate asthma symptoms lead to an increase in the number and functional impairment of Tregs, indicating that these cells play an important role in the anti-inflammatory effect of those medications.