IL-2 receptor subunit, p75: direct demonstration of its IL-2 binding ability by using a novel monoclonal antibody

A new monoclonal antibody (mAb), TU11 mAb, was found to be specific for the p75 subunit of human interleukin 2 receptor (IL-2R). TU11 mAb reacted with human and Gibbon ape cell lines positive for IL-2Rp75 but not with cell lines negative for IL-2Rp75 tested. TU11 mAb specifically detected a single cell surface molecule with a molecular weight of 75 kd. The 75 kd molecule was identical to p75 detected by TU27 mAb specific for human IL-2Rp75 in sequential immunoprecipitation. TU11 mAb did not block IL-2 binding to the high-affinity IL-2R at all and precipitated p75 bound with IL-2. Using TU11 mAb, we have demonstrated here that solubilized p75 has an IL-2 binding site.