IL4 and asthma: The allergen-specific Th2 cells orchestrate the inflammation process in asthma by producing Th2 cytokines, such as IL-4, IL-5, and IL-13, which enhance allergen-specific IgE synthesis, increase airway mucus production and the growth and differentiation of airway eosinophils, and directly induce the development of airway hyperresponsiveness (AHR), a cardinal feature of asthma [1].