Helper T cells are essential part of body's immune system. These cells are divided in many subsets based upon their ability to produce different cytokines. Following the discovery of interleukin-17 (IL-17) producing T helper (Th17) cells as a distinct lineage of T helper cells it became clear that these cells play an important role in the host defense and participate in the pathogenesis of many inflammatory and autoimmune diseases. The Th17 cells can alter their differentiation program ultimately giving rise to either protective or pro-inflammatory pathogenic cells. The protective and non-pathogenic Th17 cells are termed as Treg17 cells.