ABSTRACT
Interleukin 9 (IL-9) is a cytokine mainly produced by activated TH2 cells upon stimulation with antigen. The study of murine IL-9 originated in the search for a growth promoting activity that allowed for the antigen-independent proliferation of T helper cell clones [1]. Stable T cell lines could be derived in the absence of feeder cells and antigen, provided supernatants from activated TH2 cells were added to the culture. The growth factor present in such supernatants was further purified, designated P40, and its corresponding cDNA was cloned [2].
