The Th1/Th2 paradigm: A misrepresentation of helper T cell plasticity

For decades, the Th1/2 paradigm has been used to classify immune responses as either Th1 or Th2-biased. However, in recent years, a staggering amount of evidence has emerged to support rejection of the classical Th1/Th2 paradigm, such as the discoveries of new helper T cell subsets, helper T cell plasticity and protective mixed-Th1/Th2 responses. This opinion piece investigates the shortcomings of classical Th1/Th2 paradigm in the context of recent works, with the goal of facilitating the development of newer models to represent the diversity of Th cells.