The work presents the newest knowledge on a new phenotype of T helper lymphocytes (Th9) and on
Interleukin 9 (IL-9). Processes leading to transformation of naïve T lymphocyte into Th9 lymphocytes are presented, including the role of
IL-4 and TGFβ signaling. Involvement of
transcription factor network in production of
IL-9 is described. Other cells capable of expressing
IL-9 and secreting
IL-9 are portrayed. Diversity of
IL-9 effects caused by activation of
IL-9 receptors on various types of cells is presented. Principal effects of the activation of
IL-9 receptor on T-cells seem to be antiapoptotic and stimulatory which leads to enhanced defense against
parasitic infection and
cancer development but, from the other side, it perpetuate chronic
inflammation in
autoimmune diseases and allergic processes. In the last years the role of
IL-9 in
autoimmune diseases such as
rheumatic diseases and
inflammatory bowel disease gained importance since the increased expression of this
cytokine has been observed in animal models of intestinal
inflammation and in groups of patients with
ulcerative colitis. It was also noted that neutralization of
IL-9 in animal models of
ulcerative colitis leads to amelioration of inflammatory process, what could have significance in the treatment of this disease in humans in the future.