The Th1/Th2 concept

The Th1/Th2 concept The Th1/Th2 concept was originally defined on the basis of cytokine patterns produced by CD4+ T cell clones. Meanwhile, it has become clear that this concept can be extended to two stricingly different types of immune responses of the immune system termed T1 and T2. Whereas T1 responses refer to immunity against intracellular organisms, T2 responses are important for the clearance of extracellular pathogens like worms. In this article, the characteristics of Th1/Th2 responses, their regulatory capacities on each other and the implications of this concept for immunity and autoimmunity are being reviewed.