CD4 and asthma: The identification of CD4+ T cells expressing type 2 cytokines, such as interleukin (IL)-4, IL-5, and IL-13, in bronchial biopsy specimens and bronchial lavage fluids [2,3], as well as the recent clinical application of biomedicines against type 2 cytokines [4,5,6], further emphasizes the importance of Th2 cells in the development of asthma.