IL4 and asthma: The development of airway eosinophilia is dependent on pathological networks involving close interactions between innate as well as adaptive immunity occurring in type 2 (T2) asthma following the involvement of group 2 innate lymphoid cells (ILC2) and T helper 2 (Th2) lymphocytes; these cells produce several cytokines including interleukin-5 (IL-5), -4 (IL-4) and -13 (IL-13).