IL-23/IL-17 biology and therapeutic considerations

CD4(+) T-lymphocytes are pivotal in immune responses to pathogens and in pathogenesis of various inflammatory diseases. Upon activation by the innate immune system, naive CD4(+) helper T (T-H) -lymphocytes differentiate into effector cells that are characterized by their cytokine profiles. T-Helper 1 (T-H 1) and T(H)2 lymphocytes have long been regarded as two sides of a coin in adaptive immune responses. However, recent data indicate a novel lineage of TH lymphocytes specified by the production of interleukin-17 (IL17). Here I describe the recent literature on the regulatory mechanisms underlying generation of IL-17-expressing T-lymphocytes. In addition, I also summarize on the biological function of these cells in infection, autoimmunity and allergy. IL-17 and IL-17-expressing inflammatory TH lymphocytes may thus serve as good targets for therapeutic intervention in treatment of patients with inflammatory diseases.