IL4 and asthma: The Th2 hypothesis, first proposed by Musman in 1982, states that asthma results from a relative increment in Th2 response accompanied by a decrement in Th1 response, resulting in the increment of Th2 products (such as IL-4, IL-5, and IL-13) and a corresponding decrement of Th1 products (such as interferon gamma (IFN-γ) and IL-12) [41].