New radioimmunoassay for the detection of free IL2 receptor in supernatants of murine helper and cytotoxic T-cell lines.

Using two purified monoclonal antibodies which recognize distinct epitopes of the murine IL2 receptor, we devised a new radioimmunoassay for the detection of free IL2 receptor in lymphocyte culture supernatants. Murine cell lines of both helper and cytotoxic phenotypes produce free IL2 receptor. There appears to be a quantitative relationship between membrane IL2 receptor expression and the presence of free IL2 receptor. The latter molecule may have a biological role, possibly that of a negative signal for lymphocyte growth and/or that of an IL2 transport protein.