Detection of interleukin 2 receptors on murine lymphocytes using fluorescent interleukin 2

Murine interleukin 2 receptors found on freshly isolated and on in vitro activated lymphocytes were identified using a fluorescent interleukin 2 (IL2F). Three percent of freshly isolated small thymocytes bound the IL2F; these cells appeared to be dual CD4 and CD8 positive cells. Ten percent of the larger thymocytes also bound the IL2F; phenotypically, these cells were more heterogenous in their CD4/CD8 composition than the small IL2F+ thymocytes. Freshly isolated splenocytes bound more IL2F than did the thymocytes. Twenty-four percent of the small splenocytes were IL2F+ and they were mostly B220+ cells. Half of the larger splenocytes were IL2 receptor positive and these cells consisted of B and T cells. Using mitogen stimulated splenocytes, three times as many LPS stimulated B220+ blasts bound the fluorescent IL2 than freshly isolated large B220+ cells; this level of IL2F binding was maintained for four days. Of the Con A blasts, more CD8+ cells (30%) bound IL2F than did CD4+ blasts (19%); these cells maintained this level of IL2F binding for only three days. The IL2F binding could be completely inhibited by excess unlabeled IL2 and could be inhibited by 92% using a monoclonal antibody directed against the IL2 binding region of the IL2 alpha receptor, indicating that IL2F can bind to both IL2 alpha and IL2 beta receptors.