SHARING OF THE IL-2 RECEPTOR-GAMMA CHAIN WITH THE FUNCTIONAL IL-9 RECEPTOR COMPLEX

The third subunit, the so-called common gamma (gamma(c)) chain, of the IL-2 receptor is shared among the receptors for IL-2, IL-4, IL-7 and IL-15, and dysfunction of the gamma(c) chain is thought to cause X-linked severe combined immunodeficiency (XSCID) ascribed to impairment of early T cell development. However, cytokines linked to XSCID are as yet unidentified. A mAb specific for the gamma(c) chain, TUGm2, profoundly inhibited cell proliferation in response to IL-9. Another mAb, TUGm3, immunoprecipitated [I-125]IL-9 cross-linked with either the IL-9 receptor or the gamma(c) chain. These results demonstrate that the gamma(c) chain is included in the functional receptor complex for IL-9, which was initially characterized as a T cell growth factor and is essential for IL-9-dependent growth signal transduction.